Ethylene-nitrogen synergism induces tolerance to copper stress by modulating antioxidant system and nitrogen metabolism and improves photosynthetic capacity in mustard.

This study aimed to test the efficiency of ethylene (Eth; 200 µL L-1 ethephon) in presence or absence of nitrogen (N; 80 mg N kg-1 soil) in protecting photosynthetic apparatus from copper (Cu; 100 mg Cu kg-1 soil) stress in mustard (Brassica juncea L.) and to elucidate the physio-biochemical modulation for Eth plus N-induced Cu tolerance. Elevated Cu-accrued reductions in photosynthesis and growth were accompanied by significantly higher Cu accumulation in leaves and oxidative stress with reduced assimilation of N and sulfur (S). Ethylene in coordination with N considerably reduced Cu accumulation, lowered lipid peroxidation, lignin accumulation, and contents of reactive oxygen species (hydrogen peroxide, H2O2, and superoxide anion, O2•-), and mitigated the negative effect of Cu on N and S assimilation, accumulation of non-protein thiols and phytochelatins, enzymatic, and non-enzymatic antioxidants (activity of ascorbate peroxidase, APX, and glutathione reductase, GR; content of reduced glutathione, GSH, and ascorbate, AsA), cell viability, photosynthesis, and growth. Overall, the effect of ethylene-nitrogen synergism was evident on prominently mitigating Cu stress and protecting photosynthesis. The approach of supplementing ethylene with N may be used as a potential tool to restrain Cu stress, and protect photosynthesis and growth of mustard plants.

Genome-wide identification and expression analysis of sulfate transporter (SULTR) genes in potato (Solanum tuberosum L.).

MAIN CONCLUSION: Solanum tuberosum genome analysis revealed 12 StSULTR genes encoding 18 transcripts. Among genes annotated at group level ( StSULTR I-IV), group III members formed the largest SULTRs-cluster and were potentially involved in biotic/abiotic stress responses via various regulatory factors, and stress and signaling proteins. Employing bioinformatics tools, this study performed genome-wide identification and expression analysis of SULTR (StSULTR) genes in potato (Solanum tuberosum L.). Very strict homology search and subsequent domain verification with Hidden Markov Model revealed 12 StSULTR genes encoding 18 transcripts. StSULTR genes were mapped on seven S. tuberosum chromosomes. Annotation of StSULTR genes was also done as StSULTR I-IV at group level based mainly on the phylogenetic distribution with Arabidopsis SULTRs. Several tandem and segmental duplications were identified between StSULTR genes. Among these duplications, Ka/Ks ratios indicated neutral nature of mutations that might not be causing any selection. Two segmental and one-tandem duplications were calculated to occur around 147.69, 180.80 and 191.00 million years ago (MYA), approximately corresponding to the time of monocot/dicot divergence. Two other segmental duplications were found to occur around 61.23 and 67.83 MYA, which is very close to the origination of monocotyledons. Most cis-regulatory elements in StSULTRs were found associated with major hormones (such as abscisic acid and methyl jasmonate), and defense and stress responsiveness. The cis-element distribution in duplicated gene pairs indicated the contribution of duplication events in conferring the neofunctionalization/s in StSULTR genes. Notably, RNAseq data analyses unveiled expression profiles of StSULTR genes under different stress conditions. In particular, expression profiles of StSULTR III members suggested their involvement in plant stress responses. Additionally, gene co-expression networks of these group members included various regulatory factors, stress and signaling proteins, and housekeeping and some other proteins with unknown functions.

Calcium and Potassium Supplementation Enhanced Growth, Osmolyte Secondary Metabolite Production, and Enzymatic Antioxidant Machinery in Cadmium-Exposed Chickpea (Cicer arietinum L.).

This work examined the role of exogenously applied calcium (Ca; 50 mM) and potassium (K; 10 mM) (alone and in combination) in alleviating the negative effects of cadmium (Cd; 200 µM) on growth, biochemical attributes, secondary metabolites and yield of chickpea (Cicer arietinum L.). Cd stress significantly decreased the length and weight (fresh and dry) of shoot and root and yield attributes in terms of number of pods and seed yield (vs. control). Exhibition of decreases in chlorophyll (Chl) a, Chl b, and total Chl was also observed with Cd-exposure when compared to control. However, Cd-exposure led to an increase in the content of carotenoids. In contrast, the exogenous application of Ca and K individually as well as in combination minimized the extent of Cd-impact on previous traits. C. arietinum seedlings subjected to Cd treatment exhibited increased contents of organic solute (proline, Pro) and total protein; whereas, Ca and K-supplementation further enhanced the Pro and total protein content. Additionally, compared to control, Cd-exposure also caused elevation in the contents of oxidative stress markers (hydrogen peroxidase, H2O2; malondialdehyde, MDA) and in the activity of antioxidant defense enzymes (superoxide dismutase, SOD; catalase, CAT; ascorbate peroxidase, APX; glutathione reductase, GR). Ca, K, and Ca + K supplementation caused further enhancements in the activity of these enzymes but significantly decreased contents of H2O2 and MDA, also that of Cd accumulation in shoot and root. The contents of total phenol, flavonoid and mineral elements (S, Mn, Mg, Ca and K) that were also suppressed in Cd stressed plants in both shoot and root were restored to appreciable levels with Ca- and K-supplementation. However, the combination of Ca + K supplementation was more effective in bringing the positive response as compared to individual effect of Ca and K on Cd-exposed C. arietinum. Overall, this investigation suggests that application of Ca and/or K can efficiently minimize Cd-toxicity and eventually improve health and yield in C. arietinum by the cumulative outcome of the enhanced contents of organic solute, secondary metabolites, mineral elements, and activity of antioxidant defense enzymes.

Arsenic toxicity in garden cress (Lepidium sativum Linn.): significance of potassium nutrition.

In a hydroponic culture, experiments were performed to study the influence of potassium (K) supplementation (0, 20, 40, 60, 80, and 100 mg L(-1)) on the arsenic (As; 0, 8, and 10 mg L(-1))-accrued changes in growth traits (plant biomass, root-shoot length) and the contents of lepidine, As and K, in garden cress (Lepidium sativum Linn.) at 10 days after treatment. The changes in these traits were correlated with shoot proline content, protein profile, and the activities of antioxidant enzymes namely superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), glutathione reductase (GR, EC 1.8.1.7), and ascorbate peroxidase (APX, EC 1.11.1.11). In general, As-alone treatments significantly decreased the growth traits but lead to significant enhancements in shoot proline and enzyme activities. K-supplementation to As-treated L. sativum seedlings decreased shoot-As content, reduced As-induced decreases in growth traits but enhanced the content of shoot proline, and the activities of the studied enzymes maximally with K100 + As8 and As10 mg L(-1). Both 8 and 10 mg L(-1) of As drastically downregulated the shoot proteins ranging from 43-65 kDa. With As10 mg L(-1), there was a total depletion of protein bands below 23 kDa; however, K80 mg L(-1) maximally recovered and upregulated the protein bands. Additionally, protein bands were downregulated (at par with As-alone treatment) above K80 mg L(-1) level. Interestingly, As-stress increased lepidine content in a dose-dependent manner which was further augmented with the K-supplementation. It is suggested that K protects L. sativum against As-toxicity by decreasing its accumulation and strengthening antioxidant defense system and protein stability.