Response of adenine and pyridine metabolism during germination and early seedling growth under arsenic stress in Brassica juncea

Adenine and pyridine nucleotides play vital roles in virtually all aspects of plant growth. This study analyzed the response of adenine and pyridine metabolism during germination and early seedling growth (ESG) of Brassica juncea exposed to two doses of arsenate (AsV), 100 and 250 μM, having non-significant or significant inhibitory effects, respectively, on germination and ESG. The ratio of NAD/NADP and NAD/NADH showed no significant change in control and 100 μM AsV, but increased significantly at 250 μM AsV during initial 24 h and also at 7th day. The activity of enzymes of NAD metabolism, viz. NAD kinase, NADP phosphatase, nicotinamidase and poly(ADP-ribose) polymerases showed significant change mostly at 250 μM AsV. Further, significant decrease was observed in the ratio of ATP/ADP and in the activities of adenylate kinase and apyrase at 250 μM AsV at 7th day. External supply of ATP (1 mM) to 100 and 250 μM AsV significantly improved germination percentage and germination strength of the seeds as compared to AsV treatments alone. The study concludes that with the increase in concentration of AsV, the balance of NAD/NADP, NAD/NADH and ATP/ADP and the activities of enzymes of adenine and pyridine metabolism were significantly altered and that these changes may be responsible for inhibitory effects of AsV on germination and ESG.     

Properties of partially purified leaf ornithine aminotransferase of Brassica juncea under salt stress

Properties of the partially purified L-ornithine: 2-oxoacid aminotransferase (EC 2.6.1.13) of leaves of Brassica juncea salt tolerant somaclone SR3P6-2 and its parent cv. Prakash were studied. The enzyme from the somaclone SR3P6-2 was relatively more efficient in terms of its Km, Vmax, and Ea (activation energy) and required higher levels of chlorides for inhibition as compared to the enzyme from the parent cv. Prakash. These results suggest some salt-stress related changes in the enzyme.     

Transcriptome profiling reveals cytokinin promoted callus regeneration in Brassica juncea

Plant Cell, Tissue and Organ Culture (PCTOC) - Plant hormones not only play important roles in regulating plant growth and development, but they also promote cell dedifferentiation and...     

Kinetic and expression profiling of cytosolic pyruvate kinase enzyme during seed development of Indian mustard (Brassica juncea)

In the recent years tremendous progress has been achieved in deconstructing the oil biosynthetic pathways, majority of which is in Arabidopsis. Glycolysis is fundamental to this process as it is the cardinal supplier of precursors for fatty acid metabolism. Recent reports suggest that modification and expression of pyruvate kinase (PK), a crucial regulatory enzyme involved in glycolysis is one of the plausible ways to alter seed oil content in plants. In the present study we evaluated the kinetic behavior and expression profiling of pyruvate kinase, associated with seed development in a major oilseed crop B. juncea. Developmental profiling of the enzyme showed that enzyme activity was highest during middle stage (35 DAF) of seed development which is strongly corroborated by the expression profiling of the enzyme using RT-PCR approach. Oil accumulation pattern also correlated with the enzyme expression study. Comparative activity profiling from different tissues showed seedlings to have elevated activity than other tissues. For kinetic characterization, the enzyme was partially purified by 12.3 fold using DEAE-Sephadex column and showed a narrow pH optimum of 7.0. In presence of saturated substrate concentration, the enzyme exhibited hyperbolic kinetics for both ADP and PEP with Km (Michaelis constant value) for PEP and ADP was found to be 178.5 and 96.45 μM respectively. ATP and citrate are the most significant allosteric effectors of the partially purified PK. Study on isozymes of PK resulted in a single band.     

Quantitative proteome profiling of C. burnetii under tetracycline stress conditions

The recommended antibiotic regimen against Coxiella burnetii, the etiological agent of Q fever, is based on a semi-synthetic, second-generation tetracycline, doxycycline. Here, we report on the comparison of the proteomes of a C. burnetii reference strain either cultured under control conditions or under tetracycline stress conditions. Using the MS-driven combined fractional diagonal chromatography proteomics technique, out of the 531 proteins identified, 5 and 19 proteins were found significantly up- and down-regulated respectively, under tetracycline stress. Although the predicted cellular functions of these regulated proteins did not point to known tetracycline resistance mechanisms, our data clearly reveal the plasticity of the proteome of C. burnetii to battle tetracycline stress. Finally, we raise several plausible hypotheses that could further lead to more focused experiments on studying tetracycline resistance in C. burnetii and thus reduced treatment failures of Q fever.     

Phosphate-assisted phytoremediation of arsenic by Brassica napus and Brassica juncea: Morphological and physiological response

In this study, we examined the potential role of phosphate (P; 0, 50, 100 mg kg^?1) on growth, gas exchange attributes, and photosynthetic pigments of Brassica napus and Brassica juncea under arsenic (As) stress (0, 25, 50, 75 mg kg^?1) in a pot experiment. Results revealed that phosphate supplementation (P100) to As-stressed plants significantly increased shoot As concentration, dry biomass yield, and As uptake, in addition to the improved morphological and gas exchange attributes and photosynthetic pigments over P0. However, phosphate-assisted increase in As uptake was substantially (up to two times) greater for B. napus, notably due to higher shoot As concentration and dry biomass yield, compared to B. juncea at the P100 level. While phosphate addition in soil (P100) led to enhanced shoot As concentration in B. juncea, it reduced shoot dry biomass, primarily after 50 and 75 mg kg^?1 As treatments. The translocation factor and bioconcentration factor values of B. napus were higher than B. juncea for all As levels in the presence of phosphate. This study demonstrates that phosphate supplementation has a potential to improve As phytoextraction efficiency, predominantly for B. napus, by minimizing As-induced damage to plant growth, as well as by improving the physiological and photosynthetic attributes.     

Gene expression profiling in maize roots under aluminum stress

To investigate the molecular mechanisms of Al toxicity, cross-species cDNA array approach was employed to identify expressed sequence tags (ESTs) regulated by Al stress in root tips of Al-tolerant maize (Zea mays) genotype Cat100-6 and Al-sensitive genotype S1587-17. Due to the high degree of conservation observed between sugarcane and maize, we have analyzed the expression profiling of maize genes using 2 304 sugarcane (ESTs) obtained from different libraries. We have identified 85 ESTs in Al stressed maize root tips with significantly altered expression. Among the up-regulated ESTs, we have found genes encoding previously identified proteins induced by Al stress, such as phenyl ammonia-lyase, chitinase, Bowman-Birk proteinase inhibitor, and wali7. In addition, several novel genes up-and downregulated by Al stress were identified in both genotypes.     

不同品种芥菜对Cu胁迫响应的差异

采用水培法研究了不同品种芥菜对Cu胁迫响应的差异。结果表明:4μmol·L-1和8μmol·L-1Cu处理均抑制根和地上部生物量的积累,根受到的抑制程度大于地上部,敏感品种受到的抑制程度大于抗性品种。根中Cu积累量大于地上部,敏感品种根中Cu积累量大于抗性品种。8μmol·L-1Cu处理能明显诱导芥菜根中的MDA、Pro含量的增加及AsA含量的减少,APX、POD活性上升和GR活性下降,而不改变SOD活性。     

Proline in relation to free radical production in seedlings of Brassica juncea raised under sodium chloride stress

The production of malondialdehyde (MDA) was higher in cotyledons from NaCl-raised Brassica juncea seedlings than in control seedlings. Light accelerated the MDA-producing capacity of thylakoids isolated from both control and treated seedlings. When exposed to strong white light (920 mol photons m^-2 s^-1) the thylakoids from NaCl seedlings produced nearly 5 times more MDA than control thylakoids. In the cotyledons of NaCl seedlings, the proline level was 24-fold higher than in controls. The presence of proline during exposure of thylakoids to white light decreased MDA levels. The reduction in MDA production was higher in the thylakoids of NaCl seedlings than of controls. It is proposed that proline accumulation has an adaptive significance as it lowers the generation of free radicals and thus reduces the lipid peroxidation linked membrane deterioration under stress.     

Morphological and physio-biochemical characterization of Brassica juncea L. Czern. & Coss. genotypes under salt stress

Abstract

Soil salinity is one of the major factors responsible for the low productivity of crop plants and has become an increasing threat for agriculture. In this context, the selection of tolerant genotype/s may be one of the remedies. Keeping this in view, the effect of NaCl (0–120 mM) stress on shoot length (SL) plant^?1, area (A) leaf^?1, leaf area index (LAI), fresh weight (FW) and dry weight (DW) plant^?1, stomatal conductance (g_s), net photosynthetic rate (P _N), total chlorophyll (Chl) content, malondialdehyde (MDA) content, sensitivity rate index (SRI), leaf- nitrogen (N), potassium (K) and sodium (Na) content, leaf-K/Na ratio, nitrate reductase (NR: EC.1.6.6.1) and ATP-sulphurylase (ATP-S: EC.2.7.7.4) activities and proline (Pro) and glycinebetaine (GB) content of ten genotypes of Brassica juncea L. was studied at 55 and 65 days after sowing (DAS). NaCl treatments decreased all the above parameters, except Pro, GB, MDA, Na and SRI at both stages. Salt stress resulted in accumulation of Pro and GB, in all genotypes. The magnitude of increase in both osmolytes (Pro and GB) was higher in genotype G₈ than the other genotypes. Salt stress increased MDA and Na content while it decreased Chl, N and K content and K/Na ratio, Chl content, NR and ATP-S activities in all genotypes. But the magnitude of increase in MDA and Na content and decrease in SL plant^?1, A leaf^?1, LAI, P _N, g_s, Chl content and NR and ATP-S activities in genotype G₈ was more than that of other genotypes. These results suggest that the salt-tolerant genotype may have better osmotic adjustment and protection from free radicals by increasing the accumulation of Pro and GB content with overproduction of N and K and higher K/Na, NR and ATP-S activities under salinity stress.     

Quantitative proteomics profiling of the poly(ADP-ribose)-related response to genotoxic stress

Upon DNA damage induction, DNA-dependent poly(ADP-ribose) polymerases (PARPs) synthesize an anionic poly(ADP-ribose) (pADPr) scaffold to which several proteins bind with the subsequent formation of pADPr-associated multiprotein complexes. We have used a combination of affinity-purification methods and proteomics approaches to isolate these complexes and assess protein dynamics with respect to pADPr metabolism. As a first approach, we developed a substrate trapping strategy by which we demonstrate that a catalytically inactive Poly(ADP-ribose) glycohydrolase (PARG) mutant can act as a physiologically selective bait for the isolation of specific pADPr-binding proteins through its macrodomain-like domain. In addition to antibody-mediated affinity-purification methods, we used a pADPr macrodomain affinity resin to recover pADPr-binding proteins and their complexes. Second, we designed a time course experiment to explore the changes in the composition of pADPr-containing multiprotein complexes in response to alkylating DNA damage-mediated PARP activation. Spectral count clustering based on GeLC-MS/MS analysis was complemented with further analyses using high precision quantitative proteomics through isobaric tag for relative and absolute quantitation (iTRAQ)- and Stable isotope labeling by amino acids in cell culture (SILAC)-based proteomics. Here, we present a valuable resource in the interpretation of systems biology of the DNA damage response network in the context of poly(ADP-ribosyl)ation and provide a basis for subsequent investigations of pADPr-binding protein candidates.     

Reduced expression of BjRCE1 gene modulated by nuclear-cytoplasmic incompatibility alters auxin response in cytoplasmic male-sterile Brassica juncea

The signal from organelle to nucleus, namely retrograde regulation of nuclear gene expression, was largely unknown. Due to the nuclear-cytoplasmic incompatibility in cytoplasmic male-sterile (CMS) plants, we employed CMS Brassica juncea to investigate the retrograde regulation of nuclear gene expression in this study. We studied how reduced BjRCE1 gene expression caused by the nuclear-cytoplasmic incompatibility altered the auxin response in CMS of B. juncea. We isolated the BjRCE1 gene that was located in the nucleus from B. juncea. Over-expression of BjRCE1 enhanced auxin response in transgenic Arabidopsis. The expression of BjRCE1 was significantly reduced in CMS compared with its maintainer fertile (MF) line of B. juncea. There were fewer lateral roots in CMS than MF under normal and treatment of indole-3-acetic acid (IAA) conditions. Expression patterns of several auxin-related genes together with their phenotypes indicated a reduced auxin response in CMS compared to MF. The phenotypes of auxin response and auxin-related gene expression pattern could be mimicked by inhibiting mitochondrial function in MF. Taken together, we proposed reduced expression of BjRCE1 gene modulated by nuclear-cytoplasmic incompatibility alters auxin response in CMS B. juncea. This may be an important mechanism of retrograde regulation of nuclear gene expression in plants.     

Virulence of Agrobacterium tumefaciens strains with Brassica napus and Brassica juncea

Summary Brassica napus and Brassica juncea were infected with a number of Agrobacterium tumefaciens strains. Tumourigenesis was very rapid and extremely efficient on B. juncea with all but one of the strains. Tumourigenesis on B. napus varied widely. It was very efficient with the nopaline strains, was reduced with the succinamopine strain A281 and was very weak with the octopine strains. The latter observation was confirmed with six different B. napus rapeseed cultivars. The selectivity was due to differences in the virulence of Ti plasmids with B. napus, rather than the tumourigenicity of the T-DNA or virulence of the chromosomal genes associated with the strains. An exception was strain LBA4404. The virulence of the octopine strains was increased by coinfection with more virulent disarmed strains and by induction with acetosyringone.     

Effects of arsenite stress on growth and proteome of Klebsiella pneumoniae

In the present study an arsenite, As(III), tolerating bacterium, MR4, was isolated from Mulla River Pune, India, capable of reducing arsenate to arsenite and identified as Klebsiella pneumoniae (HQ857583). Comparative proteomic analysis using two-dimensional gel electrophoresis (2-DGE) and matrix assisted laser desorption ionization-time of flight-time of flight (MALDI-TOF/TOF) was used to monitor the proteins undergoing changes in expression levels under 2.5 mM As(III) stress. The 2-DGE proteome map has shown that 60 proteins were differentially expressed under As(III) stress, of which 39 proteins were successfully identified with a MASCOT score greater than 70 (p<0.05). Among the identified proteins, membrane transport/binding proteins, porins, and amino acid metabolism enzymes were down-regulated while stress responsive proteins and antioxidant enzymes were up-regulated. Proteins involved in carbohydrate metabolism, particularly those in pentose phosphate pathway were also up-regulated while those involved in pyruvate metabolism were down-regulated. However, proteins involved in glycolysis and tricarboxylic acid cycle showed a mixed regulation response. These findings provide new insights into the probable mechanisms by which K. pneumoniae (HQ857583) could be adapting to As(III) stress.     

Phytoremediation efficiency of Brassica juncea cultivars at vegetative and reproductive growth stages under individual and combined treatment of fluoride and aluminium

The objective of this study was to investigate phytoremediation ability of Brassica juncea cultivars for aluminium (Al) and fluoride (F) independently and in combination (Al + F). Out of 8 cultivars which were treated with Al, F, and (Al + F), 4 cultivars (Bio-902, Pusa-Tarak, CS-14, and Laxmi) were selected for further studies on the basis of growth parameters. These cultivars were exposed to soil (pH 5) supplemented with F (0, 25, 50, and 75 mg kg^?1) and Al (0, 50, 100, and 150 mg kg^?1) independently and in combination (Al + F) (0 + 0, 50 + 25, 100 + 50, and 150 + 75 mg kg^?1). We found that the accumulation of F, Al, and (Al + F) was highest in the roots followed by grains, shoots, and leaves. When the plants were treated with Al or F separately, the accumulation of Al or F were less as compared to when treated in combination (Al + F). Conclusively, the results also showed that maximum tolerance index, uptake, and translocation factor for F were highest in CS-14, Al in Bio-902, and (Al+ F) in Pusa-Tarak, and were found to be the lowest in Laxmi.