Effects of Epigenetic Mechanisms on C4 Phosphoenolpyruvate Carboxylase Transgenic Rice (Oryza sativa) Seed Germination Under Drought Stress

In order to reveal the effect of epigenetic mechanism under drought stress toward seed germination of transgenic rice within high maize C₄-type PEPC gene expressing, C₄-PEPC transgenic rice (PC) and wild type rice Kitaake (WT) were used in this study. By introducing DNA methylation inhibitor (5-azacytidine, 5azaC) and alternative splicing inhibitors (macrolides pladienolide B, PB), the drought simulation treatments with 10% (m/v) polyethylene glycol-6000 (PEG6000) alone or combining with the inhibitors were used for seed germination experiments. Seed vigor, soluble sugar and soluble protein content, α-amylase activity and the expression levels of related genes, PEPC-related genes, sugar signal-related genes, and some splicing factor genes during germination were measured. In the results, when treated with 0.25 μmol·L^-1, PB had showed a significant inhibitory effect on the seed germination of the two tested rice lines under drought conditions. The content of total soluble sugar, sucrose, glucose, fructose and soluble protein during seed germination after PB addition was reduced to a certain extent under drought conditions. PB treatment also inhibited the gene expression of sucrose nonfermenting-1 (SNF1)-related protein kinase SnRKs family and the splicing factor arginine/serine-rich proteins (SR proteins), and the activity of α-amylase as well, but the inhibitory effect on PC is less than those on WT. 5 μmol·L ^-1 5azaC treatment had an opposite effect with alternative splicing inhibitors. The combination treatment with 5azaC and PEG6000 partially alleviated the inhibitory effect of drought stress on rice seed germination, and the germination rate of the tested materials increased. It can be seen that the mechanism of DNA methylation and alternative splicing are involved in drought tolerance at the bud stage of rice lines, with a larger effect on PC.