An R2R3-Type Transcription Factor OsMYBAS1 Regulates Seed Germination under Artificial Accelerated Aging in Transgenic Rice (Oryza sativa L.)

Abstract

MYB-type transcription factors play an essential regulatory role in seed germination and the response to seedling establishment stress. This study isolated a rice R2R3-MYB transcription factor, OsMYBAS1, and functionally characterized its role in seed germination. There was no significant difference in the germination rate of each transgenic line in the standard germination test. However, compared to the germination rate of the wild type (WT) measured in the artificial accelerated aging test, the germination rates of the overexpression lines OE-OsMYBAS1-1 and OE-OsMYBAS1-2 were significantly increased by 25.0% and 21.7%, respectively. In contrast, the germination rates of the knockout mutants osmybas1-1 and osmybas1-2 were decreased by 21.7% and 33.3%, respectively. Additionally, the above data indicated that OsMYBAS1 possibly plays a positive role in rice seed germination. Moreover, the antioxidant enzyme activities of OsMYBAS1-overexpressing plants were enhanced by 38.5% to 151.0% while the superoxide dismutase (SOD) enzyme activity of osmybas1 mutants was decreased by 27.5%, and the malondialdehyde (MDA) content was increased by 24.7% on average. Interestingly, the expression of the antioxidation-related genes OsALDH3, OsAPX3, and OsCATC was enhanced in the OsMYBAS1 overexpression lines, which is consistent with the above results. Furthermore, transcriptome sequencing determined 284 differentially expressed genes (DEGs), which were mainly involved in the carbohydrate metabolic process, glycerolipid metabolism, and glycerophospholipid metabolism. Therefore, these findings provide valuable insight into the breeding of new rice varieties with high seed germination.