Role of Zn in plant physiology and growth have been extensively studied, however, its effect on the transcriptional levels of the ∆1-pyrroline-5-carboxylate synthetase (P5CS), and sucrose transporter (SUT) and starch accumulation has received less attention. The present study aimed to investigate the efficacy of Zn on P5CS and SUT1B gene expressions in a winter wheat exposed to drought stress. In addition, the role of Zn in SUT1B expression, accumulation of starch and phytic acid in grain under post-anthesis withholding-irrigation condition was also investigated. Zn was applied via different methods including foliarly, seed priming or both. As compared with the control treatment (hydro-priming), soaking seeds in 0.2% Zn (w/v) ZnSO4·7H2O solution increased seed Zn concentration from 17.74 to 430.9 μg g−1. Application of Zn via foliarly was found better than seed priming in terms of proline (Pr) accumulation and induced P5CS mRNA accumulation. Gene expression of P5CS was significantly up-regulated by drought imposition and Zn application. The SUT1B expression was significantly affected by Zn treatments. At 7 days after drought imposition, the highest expression was observed in control plants. In contrast, Zn-treated plants exhibited higher rate of SUT1B mRNA accumulation after 2 weeks after drought imposition. Plants received Zn via foliarly display grains with higher amount of Zn content than un-treated plants or primed plants. Applied Zn via foliarly was more effective in the improvment of grain Zn and grain yield than seed priming.
