Phytotoxicity of green synthesized silver nanoparticles on Camelina sativa L

Due to the increased production and release of silver nanoparticles (AgNPs) in the environment, the concerns about the possibility of toxicity and oxidative damage to plant ecosystems should be considered. In the present study, the effects of different concentrations of AgNPs (0, 0.5, 1, 2, 3 and 4 g/L) synthesized using the extract of camelina (Camelina sativa) leaves on the growth and the biochemical traits of camelina seedlings were investigated. The results showed that AgNPs significantly increased Ag accumulation in the roots and shoots which decreased the growth and photosynthetic pigments of camelina seedlings. The highest decrease in the height and total dry weight was observed by 53.1 and 61.8% under 4 g/L AgNPs, respectively over control plants. AgNPs application over 2 g/L enhanced the accumulation of proline, malondialdehyde, hydrogen peroxide and methylglyoxal, and up-regulated the activity of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase) and glyoxalase (glyoxalase I and II) system which indicates oxidative stress induction in camelina seedlings. Moreover, AgNPs reduced ASA and GSH contents and increased DHA and GSSG contents, hence disrupting the redox balance. These results showed that AgNPs at 4 g/L had the most toxic effects on the camelina growth. Therefore, increasing oxidative stress markers and the activity of antioxidant enzymes and enzymes involved in glyoxalase system indicated the oxidative stress induced by AgNPs treatments over 2 g/L as well as the induction of antioxidant defense systems to combat AgNPs-induced oxidative stress.     

Hydrogen peroxide detoxifying enzymes show different activity patterns in host and non-host plant interactions with Magnaporthe oryzae Triticum pathotype

Wheat blast caused by the hemibiotroph fungal pathogen Magnaporthe oryzae Triticum (MoT) pathotype is a destructive disease of wheat in South America, Bangladesh and Zambia. This study aimed to determine and compare the activities of antioxidant enzymes in susceptible (wheat, maize, barley and swamp rice grass) and resistant (rice) plants when interacting with MoT. The activities of reactive oxygen species-detoxifying enzymes; catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX), glutathione S-transferase (GST), peroxidase (POX) were increased in all plants in response to MoT inoculation with a few exceptions. Interestingly, an early and very high activity of CAT was observed within 24 h after inoculation in wheat, barley, maize and swamp rice grass with lower H₂O₂ concentration. In contrast, an early and high accumulation of H₂O₂ was observed in rice at 48 hai with little CAT activity only at a later stage of MoT inoculation. The activities of APX, GST and POD were also high at an early stage of infection in rice. However, these enzymes activities were very high at a later stage in wheat, barley, maize and swamp rice grass. The activity of GPX gradually decreased with the increase of time in rice. Taken together, our results suggest that late and early inductions of most of the antioxidant enzyme activities occurs in susceptible and resistant plants, respectively. This study demonstrates some insights into physiological responses of host and non-host plants when interacting with the devastating wheat blast fungus MoT, which could be useful for developing blast resistant wheat.     

Analysis of arsenic induced physiological and biochemical responses in a medicinal plant,Withania somnifera

Withania somnifera has been an important herb in the Ayurvedic and indigenous medical systems for centuries in India. However, these grow as weeds mostly in the wastelands, which receive contaminated water from municipal and industrial sources. In the present investigation, plants of Withania somnifera were exposed to various concentrations of arsenate (AsV) and arsenite (AsIII) (0, 10, 25, 50, 100 μM) for 10 days and analysed for accumulation of arsenic (As) and physiological and biochemical changes. Plants showed more As accumulation upon exposure to AsIII (320 μg g⁻¹ DW in roots and 161 μg g⁻¹ DW in leaves) than to AsV (173 μg g⁻¹ DW in roots and 100 μg g⁻¹ DW in leaves) after 10 days of treatment. Consequently, AsIII exposure caused more toxicity to plants as compared to that AsV, as evaluated in terms of the level of photosynthetic pigments and oxidative stress parameters (superoxide, hydrogen peroxide and lipid peroxidation), particularly at higher concentrations and on longer durations. Plants could tolerate low concentrations (variable for AsIII and AsV) until longer durations (10 days) and high concentrations for shorter durations (1–5 days) through increase in antioxidant enzymes and by augmented synthesis of thiols. In conclusion, As tolerance potential of Withania plants on one hand advocates its prospective use for remediation under proper supervision and on the other demonstrates possible threat of As entry into humans due to medicinal uses.     

Respiratory CO(2) as Carbon Source for Nocturnal Acid Synthesis at High Temperatures in Three Species Exhibiting Crassulacean Acid Metabolism

Temperature effects on nocturnal carbon gain and nocturnal acid accumulation were studied in three species of plants exhibiting Crassulacean acid metabolism: Mamillaria woodsii, Opuntia vulgaris, and Kalanchoë daigremontiana. Under conditions of high soil moisture, nocturnal CO₂ gain and acid accumulation had temperature optima at 15 to 20°C. Between 5 and 15°C, uptake of atmospheric CO₂ largely accounted for acid accumulation. At higher tissue temperatures, acid accumulation exceeded net carbon gain indicating that acid synthesis was partly due to recycling of respiratory CO₂. When plants were kept in CO₂-free air, acid accumulation based on respiratory CO₂ was highest at 25 to 35°C. Net acid synthesis occurred up to 45°C, although the nocturnal carbon balance became largely negative above 25 to 35°C. Under conditions of water stress, net CO₂ exchange and nocturnal acid accumulation were reduced. Acid accumulation was proportionally more decreased at low than at high temperatures. Acid accumulation was either similar over the whole temperature range (5-45°C) or showed an optimum at high temperatures, although net carbon balance became very negative with increasing tissue temperatures. Conservation of carbon by recycling respiratory CO₂ was temperature dependent. At 30°C, about 80% of the dark respiratory CO₂ was conserved by dark CO₂ fixation, in both well irrigated and water stressed plants.     

Nutritional and ecological evaluation of dairy farming systems based on concentrate feeding regimes in semi-arid environments of Jordan

The objective of this study was to evaluate the nutritional and ecological aspects of feeding systems practiced under semi-arid environments in Jordan. Nine dairy farms representing the different dairy farming systems were selected for this study. Feed samples (n = 58), fecal samples (n = 108), and milk samples (n = 78) were collected from the farms and analysed for chemical composition. Feed samples were also analysed for metabolisable energy (ME) contents and in vitro organic matter digestibility according to Hohenheim-Feed-Test. Furthermore, fecal nitrogen concentration was determined to estimate in vivo organic matter digestibility. ME and nutrient intakes were calculated based on the farmer’s estimate of dry matter intake and the analysed composition of the feed ingredients. ME and nutrient intakes were compared to recommended standard values for adequate supply of ME, utilizable crude protein, rumen undegradable crude protein (RUCP), phosphorus (P), and calcium (Ca). Technology Impact Policy Impact Calculation model complemented with a partial life cycle assessment model was used to estimate greenhouse gas emissions of milk production at farm gate. The model predicts CH₄, N₂O and CO₂ gases emitted either directly or indirectly. Average daily energy corrected milk yield (ECM) was 19 kg and ranged between 11 and 27 kg. The mean of ME intake of all farms was 184 MJ/d with a range between 115 and 225 MJ/d. Intake of RUCP was lower than the standard requirements in six farms ranging between 19 and 137 g/d, was higher (32 and 93 g/d) in two farms, and matched the requirements in one farm. P intake was higher than the requirements in all farms (mean oversupply = 19 g/d) and ranged between 3 and 30 g/d. Ca intake was significantly below the requirements in small scale farms. Milk nitrogen efficiency N-_eff (milk N/intake N) varied between 19% and 28% and was mainly driven by the level of milk yield. Total CO₂ equivalent (CO₂ equ) emission ranged between 0.90 and 1.88 kg CO₂/kg ECM milk, where the enteric and manure CH₄ contributed to 52% of the total CO₂ equ emissions, followed by the indirect emissions of N₂O and the direct emissions of CO₂ gases which comprises 17% and 15%, respectively, from total CO₂ equ emissions. Emissions per kg of milk were significantly driven by the level of milk production (r² = 0.93) and of eDMI (r² = 0.88), while the total emissions were not influenced by diet composition. A difference of 16 kg ECM/d in milk yield, 9% in N-_eff and of 0.9 kg CO₂ equ/kg in ECM milk observed between low and high yielding animals. To improve the nutritional status of the animals, protein requirements have to be met. Furthermore, low price by-products with a low carbon credit should be included in the diets to replace the high proportion of imported concentrate feeds and consequently improve the economic situation of dairy farms and mitigate CO₂ equ emissions.     

Thermal regulation of phosphoenolpyruvate carboxylase and ribulose-1,5-bisphosphate carboxylase in c(3) and c(4) plants native to hot and temperate climates

Exposure of leaf sections from 2-week-old seedlings of sorghum (Sorghum bicolor L.) (C₄ plant), corn (Zea mays L.) (C₄), peanut (Arachis hypogaea L.) (C₃ plant), and soybean (Glycine max L.) (C₃) to 40 or 45°C for up to 4 hours resulted in significant increases in the levels of 102 kilodalton (C₄), 52 kilodalton (C₃ and C₄), and 15 kilodalton (C₃ and C₄) polypeptides. These proteins comigrated, respectively, with authentic phosphoenolpyruvate carboxylase (PEPC) and the large (RLSU) and small (RSSU) subunits of ribulose-1,5-bisphosphate carboxylase (Rubisco) during both one- and two-dimensional SDS-PAGE and reacted with antisera raised against these enzymes. After 4 hours at 50°C, levels of the polypeptides either remained relatively stable (PEPC, RLSU) or increased (RSSU) in sorghum and peanut (plants native to hot climates). In corn and soybean (plants native to temperate climates), levels of the proteins either fell sharply (corn) or showed strong evidence of incomplete processing and/or aggregation (soybean). In addition to changes in levels of the proteins, the activities of PEPC and Rubisco in extracts of leaves exposed to 50°C fell by 84% and 11% of their respective control values in sorghum and by 54% each in peanut. In corn and soybean, the activities of both enzymes were depressed at 40°C, with measured values at 50°C not exceeding 5% of those from the nonstressed controls.     

Bioremoval capacity of three heavy metals by some microalgae species (Egyptian Isolates)

Three fresh water microalgal isolates [Phormidium ambiguum (Cyanobacterium), Pseudochlorococcum typicum and Scenedesmus quadricauda var quadrispina (Chlorophyta)] were tested for tolerance and removal of mercury (Hg²⁺), lead (Pb²⁺) and cadmium (Cd²⁺) in aqueous solutions as a single metal species at conc. 5–100 mg / L under controled laboratory conditions. The obtained results showed that Hg²⁺ was the most toxic of the three metal ions to the test algae even at low concentration (< 20 mg/L). While lower concentration of Pb²⁺ and Cd²⁺ (5–20 mg / L) enhanced the algal growth (chlorophyll a and protein), elevated concentrations (40–100 mg / L) were inhibitory to the growth. The results also revealed that Ph. ambiguum was the most sensitive alga to the three metal ions even at lower concentrations (5 and 10 mg / L) while P. typicum and S. quadricauda were more tolerant to high metal concentrations up to 100 mg / L. The bioremoval of heavy metal ions (Hg²⁺, Pb²⁺ and Cd²⁺) by P. typicum from aqueous solution showed that the highest percentage of metal bioremoval occurred in the first 30 min of contact recording 97% (Hg²⁺), 86% (Cd²⁺) and 70% (Pb²⁺). Transmission electron microscopy (TEM) was used to study the interaction between heavy metal ions and P. typicum cells. At ultrastructural level, an electron dense layers were detected on the algal cell surfaces when exposed to Cd, Hg and Pb. At the same time, dark spherical electron dense bodies were accumulated in the vacuoles of the algal cells exposed to Pb. Excessive accumulation of starch around the pyrenoids were recorded as well as deteriorations of the algal cell organelles exposed to the three metal ions.     

Co-overproducing Rubisco and Rubisco activase enhances photosynthesis in the optimal temperature range in rice

Rubisco limits C₃ photosynthesis under some conditions and is therefore a potential target for improving photosynthetic efficiency. The overproduction of Rubisco is often accompanied by a decline in Rubisco activation, and the protein ratio of Rubisco activase (RCA) to Rubisco (RCA/Rubisco) greatly decreases in Rubisco-overproducing plants (RBCS-ox). Here, we produced transgenic rice (Oryza sativa) plants co-overproducing both Rubisco and RCA (RBCS-RCA-ox). Rubisco content in RBCS-RCA-ox plants increased by 23%–44%, and RCA/Rubisco levels were similar or higher than those of wild-type plants. However, although the activation state of Rubisco in RBCS-RCA-ox plants was enhanced, the rates of CO₂ assimilation at 25°C in RBCS-RCA-ox plants did not differ from that of wild-type plants. Alternatively, at a moderately high temperature (optimal range of 32°C–36°C), the rates of CO₂ assimilation in RBCS-ox and RBCS-RCA-ox plants were higher than in wild-type plants under conditions equal to or lower than current atmospheric CO₂ levels. The activation state of Rubisco in RBCS-RCA-ox remained higher than that of RBCS-ox plants, and activated Rubisco content in RCA overproducing, RBCS-ox, RBCS-RCA-ox, and wild-type plants was highly correlated with the initial slope of CO₂ assimilation against intercellular CO₂ pressures (A:Ci) at 36°C. Thus, a simultaneous increase in Rubisco and RCA contents leads to enhanced photosynthesis within the optimal temperature range.

A simultaneous increase in Rubisco and RCA contents in transgenic rice leads to an enhancement of photosynthesis at moderately high temperatures within the optimal temperature range.     

Physiological and metabolic changes in two Himalayan medicinal herbs under drought,heat and combined stresses

Valeriana jatamansi Jones and Hedychium spicatum Ham-ex-Smith are important medicinal herbs of the Himalayan region, which are highly demanded by pharmaceutical industries. Climatic variability especially increasing temperature and water deficit affects the growth and productivity of these species. In addition, increased temperature and water deficit may trigger the biosynthesis of medicinally important bioactive metabolites, which influence the quality of raw plant material and finished products. Therefore, V. jatamansi and H. spicatum plants were undertaken and subjected to different levels of drought (no irrigation), heat (35 °C), and combined stresses for investigating their physiological and metabolic responses. Both the treatments (individually and in combination) reduced relative water content, photosynthesis, carboxylation efficiency, chlorophyll content, while increased intracellular CO₂, malondialdehyde and H₂O₂ content in both the species. Transpiration and stomatal conductance increased under heat and reduced under drought stress as compared to control. Water use efficiency was found to be increased under drought, while reduced under heat stress. Protein, proline, carotenoid content and antioxidant enzymes activities (superoxide dismutase, peroxidise, catalase) initially increased and thereafter decreased during late stages of stress. Exposure of plants to combined stress was more detrimental than individual stress. In V. jatamansi, exposure to drought stress significantly (p < 0.05) increased valerenic acid content in all plant parts (1.0–6.9 fold) with maximum increase after 20 days of exposure, while under heat stress, valerenic acid content increased (1.0–1.2 fold) in belowground part of V. jatamansi, and decreased (1.1–1.3 fold) in aerial part as compared to control. In H. spicatum, exposure of individual heat stress for 25–30 days and combined stress for 5–15 days significantly (p < 0.05) increased linalool content to 6.2–6.5 fold and 8.3–19.6 fold, respectively, as compared to control. Higher accumulation of bioactive compounds after exposure to mild stress provides encouraging prospects for enhancing pharmaceutical properties of these Himalayan herbs.Supplementary Information The online version contains supplementary material available at 10.1007/s12298-021-01027-w.     

Paclobutrazol mitigates salt stress in <Emphasis Type="Italic">indica</Emphasis> rice seedlings by enhancing glutathione metabolism and glyoxalase system

Stress-induced methylglyoxal (MG) functions as a toxic molecule, inhibiting plant physiological processes such as photosynthesis and antioxidant defense systems. In the present study, an attempt was made to investigate the MG detoxification through glutathione metabolism in indica rice [Oryza sativa L. ssp. indica cv. Pathumthani 1] under salt stress by exogenous foliar application of paclobutrazol (PBZ). Fourteen-day-old rice seedlings were pretreated with 15 mg L^?1 PBZ foliar spray. After 7 days, rice seedlings were subsequently exposed to 0 (control) or 150 mM NaCl (salt stress) for 12 days. Prolonged salt stress enhanced the production of MG molecules and the oxidation of proteins, leading to decreased activity of glyoxalase enzymes, glyoxalase I (Gly I) and glyoxalase II (Gly II). Consequently, the decreased glyoxalase activities were also associated with a decline in reduced glutathione (GSH) content and glutathione reductase (GR) activity. PBZ pretreatment of rice seedlings under salt stress significantly lowered MG production and protein oxidation, and increased the activities of both Gly I and Gly II. PBZ also increased GSH content and GR activity along with the up-regulation of glyoxalase enzymes, under salt stress. In summary, salinity induced a high level of MG and the associated oxidative damage, while PBZ application reduced the MG toxicity by up-regulating glyoxalase and glutathione defense system in rice seedlings.     

Adaptational changes in the lipids and fatty acid profile of the cell and thylakoid membrane of rice plants exposed to sunlight

Adaptational changes occurring in the lipids and fatty acids of the cell and the thylakoid membrane in response to high light treatment, was studied in 30 days old rice (Oryza sativa L. cv. Jyothi) plants grown under low (150–200 μmol m⁻² s⁻¹) or moderate (600–800 μmol m⁻² s⁻¹) light conditions. Results were compared with rice plants grown in high (1200–2200 μmol m⁻² s⁻¹) light conditions. Exposure of rice plants and isolated chloroplast to high light, resulted in an increase in the amount of malonaldehyde, indicating oxidation of membrane lipids. Qualitative and quantitative changes in the phosphoglycolipids and quantitative changes in neutral lipids were observed in rice plants grown under the different growth conditions. A few of the phosphoglycolipids and neutral lipids were present exclusively in plants grown at low or moderate or high light, indicating requirement of different type of lipid composition of rice plants in response to their different growth irradiances. However, no significant quantitative changes were observed in the different saturated and unsaturated fatty acid groups of total lipids in low, moderate and high light grown rice plants, as a result of exposure to high light. No qualitative changes in the fatty acid composition due to difference in growth irradiance or high light treatment were seen. The changes observed in the phosphoglycolipids and neutral lipid composition of cell and thylakoid membrane of low, moderate and high light grown rice plants in response to high light, are probably the result of physiological changes in the rice plants, to sustain optimum structure and function of the cell and thylakoid membrane to maintain active physiological functions to endure high light conditions.     

A regulatory approach on low temperature induced enzymatic and anti oxidative status in leaf of Pui vegetable (Basella alba)

Basella alba is a soft green vegetable, survives in adverse environmental circumstances, for example, very cold temperature although the mechanism and the temperature sensitivity in this species are not clarified. Pot experiment for cultivation of B. alba was carried out to examine the effects of low temperature on the synthesis of two enzymes, polyphenol oxidase (PPO) and peroxidase (POD) in leaf of this plant. They were exposed to 8 °C for 24 h, 48 h and 72 h periods and the respective controls were kept in ambient room temperature for the above mentioned time. Low temperature causes the higher activity of PPO and the threshold level was found after 48 h period when compared to the respective controls. The activity was higher at 10 mM catechol, substrate for this enzyme, than 100 mM and 200 mM concentration, however, the three doses yielded the gradual increase in activity. Similar stimulatory effects on peroxidase (POD) activity in leaf were observed whenever the plants were exposed to cold for 24 h, 48 h and 72 h periods and maximal after 48 h period. Our findings demonstrate that the higher activity of these enzymes in leaf might be an index for the regulatory mechanism of the survival of these species in such adverse environment.     

Plant growth-promoting Bacillus sp. strain SDA-4 confers Cd tolerance by physio-biochemical improvements,better nutrient acquisition and diminished Cd uptake in Spinacia oleracea L.

Cadmium (Cd) is highly toxic metal for plant metabolic processes even in low concentration due to its longer half-life and non-biodegradable nature. The current study was designed to assess the bioremediation potential of a Cd-tolerant phytobeneficial bacterial strain Bacillus sp. SDA-4, isolated, characterized and identified from Chakera wastewater reservoir, Faisalabad, Pakistan, together with spinach (as a test plant) under different Cd regimes. Spinach plants were grown with and without Bacillus sp. SDA-4 inoculation in pots filled with 0, 5 or 10 mg kg⁻¹ CdCl₂-spiked soil. Without Bacillus sp. SDA-4 inoculation, spinach plants exhibited reduction in biomass accumulation, antioxidative enzymes and nutrient retention. However, plants inoculated with Bacillus sp. SDA-4 revealed significantly augmented growth, biomass accumulation and efficiency of antioxidative machinery with concomitant reduction in proline and MDA contents under Cd stress. Furthermore, application of Bacillus sp. SDA-4 assisted the Cd-stressed plants to sustain optimal levels of essential nutrients (N, P, K, Ca and Mg). It was inferred that the characterized Cd-tolerant PGPR strain, Bacillus sp. SDA-4 has a potential to reduce Cd uptake and lipid peroxidation which in turn maintained the optimum balance of nutrients and augmented the growth of Cd-stressed spinach. Analysis of bioconcentration factor (BCF) and translocation factor (TF) revealed that Bacillus sp. SDA-4 inoculation with spinach sequestered Cd in rhizospheric zone. Research outcomes are important for understanding morpho-physio-biochemical attributes of spinach-Bacillus sp. SDA-4 synergy which might provide efficient strategies to decrease Cd retention in edible plants and/or bioremediation of Cd polluted soil colloids.     

Potential for aflatoxin B1 and B2 production by Aspergillus flavus strains isolated from rice samples

In this study, we investigated the potential for aflatoxin B₁ (AFB₁) and B₂ (AFB₂) production in rice grain by 127 strains of Aspergillus flavus isolated from rice grains collected from China. These strains were inoculated onto rice grains and incubated at 28 °C for 21 days. AFB₁ and AFB₂ were extracted and quantified by high-performance liquid chromatography coupled with fluorescence detection. Among the tested strains, 37% produced AFB₁ and AFB₂ with levels ranging from 175 to 124 101 μg kg⁻¹ for AFB₁ and from not detected to 10 329 μg kg⁻¹ for AFB₂. The mean yields of these isolates were 5884 μg kg⁻¹ for AFB₁ and 1968 μg kg⁻¹ for AFB₂. Overall, most of the aflatoxigenic strains produced higher levels of AFB₁ than AFB₂ in rice. The obtained information is useful for assessing the risk of aflatoxin contamination in rice samples.     

Effect of cadmium on the growth and antioxidant enzymes in two varieties of Brassica juncea

Increasing contamination and higher enrichment ratio of non-essential heavy metal cadmium (Cd) induce various toxic responses in plants when accumulated above the threshold level. These effects and growth responses are genotype and Cd level dependent. An experiment was conducted to analyze the effect of Cd toxicity in Brassica juncea [L] Czern and Coss by selecting its two varieties Varuna and RH-30. Cadmium (0, 25, 50 or 100 mg CdCl₂ kg⁻¹ of soil) fed to soil decreased the values of growth characteristics, activity of nitrate reductase and leaf water potential, whereas activities of antioxidant enzymes and proline content increased with the increasing concentration of Cd, observed at 30 and 60 day stages of growth, in both the varieties. Moreover, Cd uptake by the roots was higher in RH-30 than Varuna. Also the activity of antioxidant enzymes and proline accumulation were higher in Varuna with increasing soil level of Cd. Out of the two varieties, Varuna was more tolerant than RH-30 to Cd stress.     

Development of an efficient in vitro plant regeneration system amenable to Agrobacterium- mediated transformation of a recalcitrant grain legume blackgram (Vigna mungo L. Hepper)

An efficient, rapid and direct multiple shoot regeneration system amenable to Agrobacterium-mediated transformation from primary leaf with intact petiole of blackgram (Vigna mungo) is established for the first time. The effect of the explant type and its age, type and concentration of cytokinin and auxin either alone or in combination and genotype on multiple shoot regeneration efficiency and frequency was optimized. The primary leaf explants with petiole excised from 4-day-old seedlings directly developed multiple shoots (an average of 10 shoots/ explant) from the cut ends of the petiole in 95 % of the cultures on MSB (MS salts and B₅ vitamins) medium containing 1.0 μM 6-benzylaminopurine. Elongated (2–3 cm) shoots were rooted on MSB medium with 2.5 μM indole-butyric acid and resulted plantlets were hardened and established in soil, where they resumed growth and reached maturity with normal seed set. The regenerated plants were morphologically similar to seed-raised plants and required 8 weeks time from initiation of culture to establish them in soil. The regeneration competent cells present at the cut ends of petiole are fully exposed and are, thus, easily accessible to Agrobacterium, making this plant regeneration protocol amenable for the production of transgenic plants. The protocol was further successfully used to develop fertile transgenic plants of blackgram using Agrobacterium tumefaciens strain EHA 105 carrying a binary vector pCAMBIA2301 that contains a neomycin phosphotransferase gene (nptII) and a β-glucuronidase (GUS) gene (uidA) interrupted with an intron. The presence and integration of transgenes in putative T₀ plants were confirmed by polymerase chain reaction (PCR) and Southern blot hybridization, respectively. The transgenes were inherited in Mendelian fashion in T₁ progeny and a transformation frequency of 1.3 % was obtained. This protocol can be effectively used for transferring new traits in blackgram and other legumes for their quantitative and qualitative improvements.     

Structural Transitions and Energy Landscape for Cowpea Chlorotic Mottle Virus Capsid Mechanics from Nanomanipulation in?Vitro and in Silico

Physical properties of capsids of plant and animal viruses are important factors in capsid self-assembly, survival of viruses in the extracellular environment, and their cell infectivity. Combined AFM experiments and computational modeling on subsecond timescales of the indentation nanomechanics of Cowpea Chlorotic Mottle Virus capsid show that the capsid’s physical properties are dynamic and local characteristics of the structure, which change with the depth of indentation and depend on the magnitude and geometry of mechanical input. Under large deformations, the Cowpea Chlorotic Mottle Virus capsid transitions to the collapsed state without substantial local structural alterations. The enthalpy change in this deformation state ΔH_ind = 11.5–12.8 MJ/mol is mostly due to large-amplitude out-of-plane excitations, which contribute to the capsid bending; the entropy change TΔS_ind = 5.1–5.8 MJ/mol is due to coherent in-plane rearrangements of protein chains, which mediate the capsid stiffening. Direct coupling of these modes defines the extent of (ir)reversibility of capsid indentation dynamics correlated with its (in)elastic mechanical response to the compressive force. This emerging picture illuminates how unique physico-chemical properties of protein nanoshells help define their structure and morphology, and determine their viruses’ biological function.     

ABA and BAP improve the accumulation of carbohydrates and alter carbon allocation in potato plants at elevated CO2

Elevated CO₂ interactions with other factors affects the plant performance. Regarding the differences between cultivars in response to CO₂ concentrations, identifying the cultivars that better respond to such conditions would maximize their potential benefits. Increasing the ability of plants to benefit more from elevated CO₂ levels alleviates the adverse effects of photoassimilate accumulation on photosynthesis and increases the productivity of plants. Despite its agronomic importance, there is no information about the interactive effects of elevated CO₂ concentration and plant growth regulators (PGRs) on potato (Solanum tuberosum L.) plants. Hence, the physiological response and source-sink relationship of potato plants (cvs. Agria and Fontane) to combined application of CO₂ levels (400 vs. 800 µmol mol⁻¹) and plant growth regulators (PGR) [6-benzylaminopurine (BAP) + Abscisic acid (ABA)] were evaluated under a controlled environment. The results revealed a variation between the potato cultivars in response to a combination of PGRs and CO₂ levels. Cultivars were different in leaf chlorophyll content; Agria had higher chlorophyll a, b, and total chlorophyll content by 23, 43, and 23%, respectively, compared with Fontane. The net photosynthetic rate was doubled at the elevated compared with the ambient CO₂. In Agria, the ratio of leaf intercellular to ambient air CO₂ concentrations [C_i:C_a] was declined in elevated-CO₂-grown plants, which indicated the stomata would become more conservative at higher CO₂ levels. On the other hand, the increased C_i:C_a in Fontane showed a stomatal acclimation to higher CO₂ concentration. The higher leaf dark respiration of the elevated CO₂-grown and BAP + ABA-treated plants was associated with a higher leaf soluble carbohydrates and starch content. Elevated CO₂ and BAP + ABA shifted the dry matter partitioning to the belowground more than the above-media organs. The lower leaf soluble carbohydrate content and greater tuber yield in Fontane might indicate a more efficient photoassimilate translocation than Agria. The results highlighted positive synergic effects of the combined BAP + ABA and elevated CO₂ on tuber yield and productivity of the potato plants.     

Elevated seawater temperature causes a microbial shift on crustose coralline algae with implications for the recruitment of coral larvae

Crustose coralline algae (CCA) are key reef-building primary producers that are known to induce the metamorphosis and recruitment of many species of coral larvae. Reef biofilms (particularly microorganisms associated with CCA) are also important as settlement cues for a variety of marine invertebrates, including corals. If rising sea surface temperatures (SSTs) affect CCA and/or their associated biofilms, this may in turn affect recruitment on coral reefs. Herein, we report that the CCA Neogoniolithon fosliei, and its associated microbial communities do not tolerate SSTs of 32 °C, only 2–4 °C above the mean maximum annual SST. After 7 days at 32 °C, the CCA exhibited clear signs of stress, including bleaching, a reduction in maximum quantum yield (F_v/F_m) and a large shift in microbial community structure. This shift at 32 °C involved an increase in Bacteroidetes and a reduction in Alphaproteobacteria, including the loss of the primary strain (with high-sequence similarity to a described coral symbiont). A recovery in F_v/F_m was observed in CCA exposed to 31 °C following 7 days of recovery (at 27 °C); however, CCA exposed to 32 °C did not recover during this time as evidenced by the rapid growth of endolithic green algae. A 50% reduction in the ability of N. fosliei to induce coral larval metamorphosis at 32 °C accompanied the changes in microbiology, pigmentation and photophysiology of the CCA. This is the first experimental evidence to demonstrate how thermal stress influences microbial associations on CCA with subsequent downstream impacts on coral recruitment, which is critical for reef regeneration and recovery from climate-related mortality events.