Recently, Li Li’s team from the Hybrid Rice Research Center published a research paper entitled”EMBRYO SAC DEVELOPMENT 1 affects seed setting rate in rice by controlling embryo sac development” in Plant Physiology, an international authoritative journal of botany. , Revealing that the egg-shaped family protein EMBRYO SAC DEVELOPMENT 1 (ESD1) affects the seed setting rate by regulating the development of rice embryo sacs.
Seed setting rate is one of the key factors that determine rice yield. Therefore, in-depth study of the mechanism that affects seed setting rate is of great significance to increase rice yield. Embryo sac is an important part of rice spikelet, and its development directly affects the seed setting rate. Oval family proteins (OFP) play a key role in regulating the growth and development of plants, including fruit ripening and quality formation, DNA repair, secondary cell wall formation and embryo sac development. In addition, the team’s previous research found that OFP family protein ESD1 is mainly highly expressed in rice panicles.
In this study, in situ hybridization combined with RT-qPCR results showed that during the development of rice panicles, ESD1 mainly functions in the ovule and localization of the expressed protein In the cytoplasm. The loss-of-function mutant esd1 of ESD1 was obtained using CRISPR/Cas9 technology; phenotypic analysis showed that the plant height, number of grains per ear, number of tillers, and 1000-grain weight of the esd1 mutant were not significantly different from those of the wild type, but the seed setting rate was significantly reduced . Further research found that the stamen development and pollen tube growth of the mutant esd1 were normal. The detection of fertilization rate of spikelet spikelets of mutant esd1, as well as the statistical results of cross and saturated pollination, further showed that the anther development of mutant esd1 was normal, and the reason for the decrease in seed setting rate occurred before fertilization. The results of mature embryo sac structure detection showed that during the mitosis of the functional megaspore, the egg cells of the mutant esd1 part of the embryo sac were degraded during the differentiation process, which hindered the subsequent fertilization and ultimately reduced the seed setting rate. In addition, the transcription level detection of genes involved in rice embryo sac development combined with transcriptome data analysis revealed that the expression of the embryo sac development gene OsAPC6 was significantly down-regulated in the mutant esd1. OsAPC6 encodes a cell cycle-related ubiquitin ligase, which can degrade mitosis-related regulatory factors through the ubiquitin-proteasome pathway. Therefore, the ubiquitin-mediated protein degradation pathway may be involved in the regulation of rice embryo sac development.
In short, this study shows that ESD1, as a key regulator of rice seed setting rate, is of great significance for increasing rice yield. The research results not only help to further clarify the regulation mechanism of embryo sac development, but also have high theoretical value in revealing the molecular mechanism of rice grain formation. Assistant researcher Wang Tiankang is the first author of the paper, researcher Li Li is the corresponding author of the paper, and Professor Wang Jianlong of Hunan Agricultural University is the co-corresponding author of the paper.