The Crucial Role Of Gibberellic Acid On Germination Of Drought-Resistant Upland Rice

Drought is one of the main factors restricting seed germination. In order to reveal the physiological and molecular mechanisms of improved germination ability in upland rice under drought stress, we investigated the seed germination characteristics and the expression of genes related to gibberellic acid (GA3), alpha-amylase, and expansin of upland rice cultivar IRAT109 and lowland rice cultivar Yuefu under drought stress induced by 15 % (m/v) polyethylene glycol (PEG) and GA3 application. Seed germination decreased in upland rice and lowland rice under PEG-induced stress; upland rice was less affected than lowland rice. The germination vigour, root length, and shoot length were significantly higher in upland rice than in lowland rice under PEG stress. The GA3/abscisic acid ratio, alpha-amylase activity, and soluble sugar content in the germinated seeds were higher in upland rice. An RNA sequencing analysis revealed that 14 genes related to gibberellins, alpha-amylase, and expansin had a significantly higher expression in upland rice than in lowland rice. On the other hand, application of GA3 significantly increased the germination vigour, shoot length, root length, alpha-amylase activity, and soluble sugar content in upland rice. It also induced higher expressions of alpha-amylase and expansin related genes in upland rice. The results indicate that GA3 plays an important role in promoting seed germination in upland rice under drought stress by increasing the expressions of alpha-amylase and expansin genes.