Effect of PEG-induced drought stress on seed germination of four lentil genotypes

Seeds of four lentil genotypes (Castelluccio, Eston, Pantelleria, and Ustica) were subjected to five levels (0, 10, 15, 18, and 21%) of polyethylene glycol (PEG-6000). Germination percentage, root length, tissue water content (WC), α- and β-amylases, α-glucosidase activities, and osmolyte content were evaluated at 24, 48, and 72 h after starting the germination test. Water stress reduced seed germination percentage, root length, and seedling WC in all cultivars to different extent. The increase in proline content and total soluble sugars was greater for Eston and Castelluccio compared to the other genotypes. The activity of the enzymes involved in the germination process decreased in all cultivars; the activities of α-amylase and α-glucosidase were most negatively affected by osmotic stress, mainly in the drought sensitive Ustica and Pantelleria. Overall, Eston and Castelluccio were able to express greater drought tolerance and consequently could be used as a valuable resource for breeding programs.     

不同基因型茶菊对盐胁迫的响应

为探讨不同基因型茶菊(tea Chrysanthemum)在盐胁迫下的生理响应并对其进行耐盐性评价, 以4个不同基因型茶菊为材料, 采用营养液浇灌法, 研究了不同浓度NaCl (0、40、80、120、160、200 mmol·L^-1)胁迫下茶菊生理生化和光合生理响应特性。结果表明: 随着NaCl胁迫程度加大, 不同基因型茶菊叶片细胞膜透性(Cond)、丙二醛(MDA)含量、叶片脯氨酸(Pro)含量和可溶性糖(SS)含量增加; 超氧化物歧化酶(SOD)含量呈先升后降趋势; ‘乳荷’、‘黄滁龙’叶绿素(Chl)含量持续下降, ‘繁白露’和‘玉人面’叶绿素含量呈先升后降的趋势; 净光合速率(P_n)、蒸腾速率(T_r)和气孔导度(G_s)随NaCl胁迫浓度提高而极显著降低, 气孔限制值呈先升后降的趋势。采用隶属函数法对茶菊进行耐盐性评价, 不同基因型茶菊耐盐性由强到弱依次为‘乳荷’ > ‘玉人面’ > ‘繁白露’ > ‘黄滁龙’。其中, 耐盐性品种‘玉人面’、‘乳荷’在NaCl胁迫下, Chl含量、P_n、T_r和G_s下降幅度小, MDA含量和气孔限制值增幅较小。     

Proteomic profiling of aphid Macrosiphum euphorbiae responses to host-plant-mediated stress induced by defoliation and water deficit

Abiotic and biotic host-plant stress, such as desiccation and herbivory, may strongly affect sap-sucking insects such as aphids via changes in plant chemicals of insect nutritional or plant defensive value. Here, we examined (i) water deprivation and (ii) defoliation by the beetle Leptinotarsa decemlineata as stresses indirectly affecting the aphid Macrosiphum euphorbiae via its host plant Solanum tuberosum. For plant-induced stress, aphids were reared on healthy vs. continuously stressed potato for 14 days (no watering; defoliation maintained at approximately 40%). Aphid performance under stress was correlated with metabolic responses monitored by profiling of the aphid proteome. M. euphorbiae was strongly affected by water stress, as adult survival, total aphid number and biomass were reduced by 67%, 64%, and 79%, respectively. Aphids performed normally on defoliated potato, indicating that they were unaffected or able to compensate any stress induced by plant defoliation. Stressed aphid proteomes revealed 419-453 protein spots, including 27 that were modulated specifically or jointly under each kind of host-plant stress. Reduced aphid fitness on water-stressed plants mostly correlated with modulation of proteins involved in energy metabolism, apparently to conserve energy in order to prioritize survival. Despite normal performance, several aphid proteins that are known to be implicated in cell communication were modulated on defoliated plants, possibly suggesting modified aphid behaviour. The GroEL protein (or symbionin) of the endosymbiont Buchnera aphidicola was predominant under all conditions in M. euphorbiae. Its expression level was not significantly affected by aphid host-plant stresses, which is consistent with the high priority of symbiosis in stressed aphids.     

Germination and seedling growth of carrots under salinity and moisture stress

Poor crop stand is a common problem in saline areas. Germination and seedling emergence may be depressed as a result of impeded aeration, saline or dry conditions. In this study, we examined the effects of salinity and moisture stress and their interactions on seed germination and seedling growth of carrots. Variable soil matric and osmotic potentials were either obtained by equilibrating soil salinized to different degrees on a 0.5 MPa ceramic plate soil moisture extractor or by adding different amounts of salt solutions to the same mass of air-dried soil, based on a previously determined soil moisture release curve, and allowing to equilibrate for 1 week. Germination decreased significantly in the investigated silty soil (Aquic Ustifluvent) at soil moisture potentials higher than −0.01 MPa, whereas osmotic potentials as low as −0.5 MPa did not influence germination. Matric potentials of −0.3 and −0.4 MPa, respectively, resulted in a strong decrease (35–95%) of germination and delayed germination by 2 to 5 days in the silty soil to which different amounts (18 and 36%, respectively) and sizes (0.8–1.2 mm and 1.5–2.2 mm, respectively) of sand particles had been added. No effect of sand and grain diameter was detected. Germination was not affected by comparable osmotic potentials. Seedling growth showed a much higher sensitivity than germination to decreasing matric potentials, but was not affected by osmotic potentials ranging from −0.05 to −0.5 MPa. Optimum shoot growth occurred at matric potentials between −0.025 and −0.1 MPa. Shoot and root growth decreased markedly at matric potentials higher than −0.01 MPa. Fresh weight of shoots decreased gradually at matric potentials lower than −0.2 MPa. Root growth was significantly increased at matric potentials of −0.1 to −0.3 MPa, whereas comparable osmotic potentials did not have equivalent effects. It is concluded that germination and seedling growth are differently affected by comparable matric and osmotic stresses and that water stress exerts a more negative effect than salt stress.     

Proteome-level changes in the roots of Pisum sativum in response to salinity

We initiated a proteomics-based approach to identify root proteins affected by salinity in pea (Pisum sativum cv. Cutlass). Salinity stress was imposed either on 2-wk old pea plants by watering with salt water over 6 wk or by germinating and growing pea seeds for 7 days in Petri dishes. Concentrations of NaCl above 75 mM had significant negative effects on growth and development of peas in both systems. Salinity-induced root proteome-level changes in pea were investigated by 2-D electrophoresis of proteins from control, 75 and 150 mM NaCl-treated plants and seedlings. The majority of the protein spots visualised showed reproducible abundance in root protein extracts from whole plants and seedlings. Of these proteins, 35 spots that exhibited significant changes in abundance due to NaCl treatment were selected for identification using ESI-Q-TOF MS/MS. The identities of these proteins, which include pathogenesis-related (PR) 10 proteins, antioxidant enzymes such as superoxide dismutase (SOD) as well as nucleoside diphosphate kinase (NDPK) are presented, and the roles of some of them in mediating responses of pea to salinity are discussed. This is the first report of salinity-induced changes in the root proteome of pea that suggests a potential role for PR10 proteins in salinity stress responses. Our findings also suggest the possible existence of a novel signal transduction pathway involving SOD, H₂O₂, NDPK and PR10 proteins with a potentially crucial role in abiotic stress responses.     

Function of a novel GDSL-type pepper lipase gene, <Emphasis Type="Italic">CaGLIP1</Emphasis>, in disease susceptibility and abiotic stress tolerance

GDSL-type lipase is a hydrolytic enzyme whose amino acid sequence contains a pentapeptide motif (Gly-X-Ser-X-Gly) with active serine (Ser). Pepper GDSL-type lipase (CaGLIP1) gene was isolated and functionally characterized from pepper leaf tissues infected by Xanthomonas campestris pv. vesicatoria (Xcv). The CaGLIP1 protein was located in the vascular tissues of Arabidopsis root. The CaGLIP1 gene was preferentially expressed in pepper leaves during the compatible interaction with Xcv. Treatment with salicylic acid, ethylene and methyl jasmonate induced CaGLIP1 gene expression in pepper leaves. Sodium nitroprusside, methyl viologen, high salt, mannitol-mediated dehydration and wounding also induced early and transient CaGLIP1 expression in pepper leaf tissues. Virus-induced gene silencing of CaGLIP1 in pepper conferred enhanced resistance to Xcv, accompanied by the suppressed expression of basic PR1 (CaBPR1) and defensin (CaDEF1) genes. The CaGLIP1 lipase produced in Escherichia coli hydrolyzed the substrates of short and long chain nitrophenyl esters. The CaGLIP1-overexpressing Arabidopsis exhibited enhanced hydrolytic activity toward short and long chain nitrophenyl ester, as well as enhanced susceptibility to the bacterial pathogen Pseudomonas syringae pv. tomato and the biotrophic oomycete Hyaloperonospora parasitica. SA-induced expression of AtPR1 and AtGST1, also was delayed in CaGLIP1-overexpressing plants by SA application. During seed germination and plant growth, the CaGLIP1 transgenic plants showed drought tolerance and differential expression of drought- and abscisic acid (ABA)-inducible genes AtRD29A, AtADH and AtRab18. ABA treatment differentially regulated seed germination and gene expression in wild-type and CaGLIP1 transgenic Arabidopsis. Overexpression of CaGLIP1 also regulated glucose- and oxidative stress signaling. Together, these results indicate that CaGLIP1 modulates disease susceptibility and abiotic stress tolerance. The nucleotide sequence data reported here has been deposited in the GenBank database under the accession number AY775336.     

The molecular mechanism of plasma membrane H+-ATPases in plant responses to abiotic stress

Plasma membrane H⁺-ATPases (PM H⁺-ATPases) are critical proton pumps that export protons from the cytoplasm to the apoplast. The resulting proton gradient and difference in electrical potential energize various secondary active transport events. PM H⁺-ATPases play essential roles in plant growth, development, and stress responses. In this review, we focus on recent studies of the mechanism of PM H⁺-ATPases in response to abiotic stresses in plants, such as salt and high pH, temperature, drought, light, macronutrient deficiency, acidic soil and aluminum stress, as well as heavy metal toxicity. Moreover, we discuss remaining outstanding questions about how PM H⁺-ATPases contribute to abiotic stress responses.     

Comprehensive physiological analyses and reactive oxygen species profiling in drought tolerant rice genotypes under salinity stress

Rice being a staple cereal is extremely susceptible towards abiotic stresses. Drought and salinity are two vital factors limiting rice cultivation in Eastern Indo-Gangetic Plains (EIGP). Present study has intended to evaluate the consequences of salinity stress on selected drought tolerant rice genotypes at the most susceptible seedling stage with an aim to identify the potential multi-stress (drought and salt) tolerant rice genotype of this region. Genotypic variation was obvious in all traits related to drought and salt susceptibility. IR84895-B-127-CRA-5-1-1, one of the rice genotypes studied, exhibited exceptional drought and salinity tolerance. IR83373-B-B-25-3-B-B-25-3 also displayed enhanced drought and salt tolerance following IR84895-B-127-CRA-5-1-1. Variations were perceptible in different factors involving photosynthetic performance, proline content, lipid peroxidation, K⁺/Na⁺ ratio. Accumulation of reactive oxygen species (ROS) disintegrated cellular and sub-cellular membrane leading to decreased photosynthetic activities. Therefore, accumulation and detoxification of reactive oxygen species was also considered as a major determinant of salt tolerance. IR84895-B-127-CRA-5-1-1 showed improved ROS detoxification mediated by antioxidant enzymes. IR84895-B-127-CRA-5-1-1 seedlings also displayed significant recovery after removal of salt stress. The results established a direct association of ROS scavenging with improved physiological activities and salt tolerance. The study also recommended IR84895-B-127-CRA-5-1-1 for improved crop performance in both drought and saline environments of EIGP. These contrasting rice genotypes may assist in understanding the multiple stress associated factors in concurrent drought and salt tolerant rice genotypes.     

不同盐度胁迫下杜氏盐藻全转录组测序及注释

【目的】通过对杜氏盐藻的转录组进行测序和基因功能分析,阐明不同浓度盐胁迫对杜氏盐藻生长发育以及不同信号途径的影响。【方法】分别获取9%NaCl浓度和24%NaCl浓度培养下的杜氏盐藻转录组并通过Illumina平台进行测序。将所得的序列进行拼接、去冗余处理。【结果】获得40682个unigenes,其中注释到NR数据库的10905个,注释到NT数据库的2768个,注释到SWISS-PROT数据库的7261个,注释到COG/KOG数据库的6499个。受到高盐胁迫的杜氏盐藻细胞相比低盐环境下,有717个基因表达上调,1012个基因表达下调。进一步对60个显著差异基因进行了功能聚类,发现盐胁迫诱导了光合作用途径的基因表达。【结论】杜氏盐藻通过提高光合作用基因表达增强耐盐性。该研究最大范围上挖掘了杜氏盐藻在高盐和低盐环境的基因转录水平,为深入揭示杜氏盐藻盐胁迫下基因差异表达提供了平台,并为进一步研究杜氏盐藻耐盐机理提供理论依据。     

Distinct physiological responses of two rice cultivars subjected to iron toxicity under field conditions

Iron toxicity is recognised as the most widely distributed nutritional disorder in lowland and irrigated rice, derived from the excessive amounts of ferrous ions generated by the reduction of iron oxides in flooded soils. Rice cultivars with variable degrees of tolerance to iron toxicity have been developed, and cultural practices such as water management and fertilisation can be used to reduce its negative impact. However, because of the complex nature of iron toxicity, few physiological data concerning tolerance mechanisms to excess iron in field conditions are available. To analyse the physiological responses of rice to iron excess in field conditions, two rice cultivars with distinct tolerance to iron toxicity [BR‐IRGA 409 (susceptible) and IRGA 420 (tolerant)] were grown in two areas, with a well‐established history of iron toxicity (in Camaquã, RS, Brazil) and without iron toxicity (in Cachoeirinha, RS, Brazil). Plants from the susceptible cultivar grown in the iron‐toxic site showed lower levels of chlorophylls and soluble proteins (together with higher carbonyl levels) indicating photooxidative and oxidative damage. The toxic effects observed were because of the accumulation of high levels of iron and not because of any indirectly induced shoot deficiency of other nutrients. Higher activities of antioxidative enzymes were also observed in leaves of plants from the susceptible cultivar only in the iron‐toxic site, probably as a result of oxidative stress rather than because of specific involvement in a tolerance mechanism. There was no difference between cultivars in iron accumulation in the symplastic and apoplastic space of leaves, with both cultivars accumulating 85–90% of total leaf iron in the symplast. However, susceptible plants accumulated higher levels of iron in low‐molecular‐mass fractions than tolerant plants. The accumulation of iron in the low‐molecular‐mass fraction probably has a direct influence on iron toxicity, and the adaptive strategy of tolerant plants may rely on their capacity to buffer the iron amounts present in the low mass fraction, a new parameter to be considered when evaluating tolerance to iron excess in field‐cultivated rice plants.