Effect of drought stress on the expression of genes linked to antioxidant enzymatic activity in landraces of Zea mays L. and Pennisetum glaucum (L.) R. Br.

Millets are usually considered more drought tolerant than other cereals. Pearl millet [Pennisetum glaucum (L.) R. Br.] could be an alternative to maize (Zea mays L.) for drought hit regions of the world. In this current study, the sensitivity of these two plants was evaluated under a simulated condition of drought stress. Genotypes IP35451 (pearl millet) and LRN1303 (maize) were compared for their tolerance to drought stress. The growth parameters viz., root/shoot ratio and relative water content were reduced drastically in LRN1303 than in IP35451. Photosystem II was also measured and the study revealed a decrease in electron transport rate and photosynthetically active photo flux density in LRN1303 as compared to IP35451 which had an efficient photosynthesis capacity during drought. Malondialdehyde content and concentration of antioxidant enzymes (Ascorbate peroxidase, Catalase, Glutathione reductase and Superoxide dismutase) revealed that the genotype IP35451 (pearl millet) is better adapted to drought as compared to LRN1303 (maize). Moreover, the gene expression study of three identified genes at transcript levels proved their occurrence as indicators for drought tolerance. GBSS11a in leaf and root displayed steady up-regulation under drought stress in IP35451 (pearl millet), and an initial increase with a subsequent down-regulation in LRN1303 (maize). Expression of antioxidant genes revealed that APX1 and CAT1 in leaves and roots were more remarkably sensitive to drought in IP35451 (pearl millet), however, not for LRN1303 (maize) where they might support better detoxifying action against reactive oxygen species effect under drought condition. The results showed different capacities of LRN1303 (maize) and IP35451 (pearl millet) to activate expression of drought related mRNA. The outcome of the study will be helpful to provide new avenues in future research related to attaining drought tolerant landraces and their genomics.