Effect of selenium and silicon on transcription factors NAC5 and DREB2A involved in drought-responsive gene expression in rice

Drought is one of the main environmental stresses and many investigators identified beneficial effects of both silicon and selenium on plant growth and development. To examine the effects of Si and Se on rice (Oryza sativa L.) responses to drought, two cultivars Giza 177 and IET 1444 pretreated with 1.5 mM Si or 0.03 mM Se were then exposed to a water stress until leaf rolling was observed. The enhanced growth of Se or Si pre-treated plants was associated with a significant increase in the content of proline and glycine betaine in both shoots and roots. Furthermore, the transcription factors (TFs), dehydration responsive element-binding protein DREB2A, and NAC5 [no apical meristem (NAM), Arabidopsis thaliana activating factor (ATAF), and cup-shaped cotyledon (CUC)] were over-expressed in the drought stressed rice shoots. Notably, a pretreatment with either Se or Si significantly enhanced the expression of both TFs, DREB2A, NAC5, as well as the expression of the ring domain containing OsRDCP1 gene and some drought specific genes, such as OsCMO coding rice choline monooxygenase and dehydrin OsRAB16b. Expression of TFs and the studied genes was markedly enhanced in the Si-stressed shoots of cv. IET 1444 which favors its drought tolerance.