Browsing by Author "Misra, Shrilekha"

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A comprehensive study on dehydration-induced antioxidative responses during germination of Indian bread wheat (Triticum aestivum L. em Thell) cultivars collected from different agroclimatic zones
(Springer Science, 2012) Garg, Bharti; Jaiswal, Jai P.; Misra, Shrilekha; Tripathi, Bhumi Nath; Prasad, Manoj
To explore the adaptability of bread wheat to dehydration stress, we screened 28 cultivars collected from different agroclimatic zones, on the basis of malonaldehyde content as biochemical marker in roots of wheat seedlings during germination and classified them as highly tolerant, tolerant, sensitive and highly sensitive. From this primary screening, ten cultivars that showed differential responses to dehydration stress were selected to understand the biochemical and physiological basis of stress tolerance mechanisms. The highly tolerant cultivars showed lower levels of lipid peroxidation, less membrane damage, increased levels of antioxidants, enzymes like catalase, ascorbate peroxidase, glutathione reductase activities, and maintained higher relative water content in comparison to sensitive cultivars, indicating better protection mechanism operating in tolerant cultivars. Correspondingly, highly tolerant cultivars exhibited more accumulation of proline and less H2O2 content across different time points of polyethylene glycol treatments in comparison to sensitive ones. The above biochemical and physiological parameters were further validated through northern analysis of catalase (CAT1) gene, that showed differential expression patterns in tolerant and sensitive cultivars largely in confirmation with the biochemical and physiological analyses. Our study positively correlates the differences in the redox status and antioxidant defense system between tolerant and sensitive cultivars for the establishment of wheat seedlings in typical dehydration conditions.
Transcript profiling identifies novel transcripts with unknown functions as primary response components to osmotic stress in wheat (Triticum aestivum L.)
(Springer, 2013) Garg, Bharti; Puranik, Swati; Misra, Shrilekha; Tripathi, Bhumi Nath; Prasad, Manoj
Osmotic stress induced by dehydration and salinity, is among the major abiotic stresses that adversely impacts crop productivity and plants often display cultivar-dependent response against osmotic imbalance. To better understand the molecular mechanisms underlying differential responses to dehydration, transcriptome changes of two contrasting wheat (Triticum aestivum L.) cultivars were evaluated in plants grown under unfavorable osmotic conditions. A total of 107 non-redundant transcripts were identified. Of these, most had unknown functions (31; ~30 %) signifying the existence of putative stress-specific genes in wheat, reported here for the first time. Upon comparing with previous transcriptomic studies, 43 (40 %) of the osmotically-responsive transcripts were found not to be documented. These new transcripts may therefore signify unexplored gene sources for specific responses towards short-term osmotic stress in wheat. Through macroarray analysis, 69 (~64 %) transcripts were found to be differentially expressed (≥3-fold) and expression of 14 transcripts (with known or unknown functions) was further confirmed by quantitative real time PCR. Expression analysis of the seven unknown transcripts also revealed their tissue- and stress-specific regulation. Comparative in silico mapping of these 107 wheat transcripts against available mapping data for rice (40; ~37 %), maize (34; ~32 %), and sorghum (33; ~31 %) revealed presence of wheat orthologous sequences in these cereal crops. This study provides an interesting account on several novel genes, besides those with known functions, which may regulate stress response dynamics and thus, may be used as potential candidates to improve stress adaptability through genetic and molecular studies.