On May 9th, Academician Wan Jianmin's team and Jia Guifang's team from Peking University published a paper titled The RNA binding protein EHD6 recruits the m6A reader YTH07 and sequesters OsCOL4mRNA into phase-separated ribonucleoprotein condensates to in Molecular Plant Research paper promoting rice flowering. This paper revealed the mechanism by which RNA-binding proteins regulate rice heading stage through phase separation mediated by the m6A pathway. Rice is one of the most important food crops in the world, and heading stage is a key trait that determines the regional and seasonal adaptability of varieties, which affects the yield and quality of rice. It is of great significance to explore new genes at heading stage and analyze the molecular regulation mechanism at heading stage for cultivating rice varieties with high yield, high quality and wide adaptability. m6A refers to the methylation modification that occurs at the N6 position of adenine in the RNA molecule and is one of the most common and important RNA modifications in eukaryotic mRNA. It was found that the modification was recognized by the m6A reader and had biological functions such as affecting mRNA stability, splicing of precursor RNA, selective polyadenylation and promoting translation. However, it is unclear whether the heading stage of rice is regulated by the m6A pathway. In addition, recent studies have found that m6A is also involved in the process of translation inhibition, but its molecular mechanism still needs to be elucidated. In this study, a gene Early Heading Date 6 (EHD6) was cloned to promote rice heading in both long and short days. This gene encodes an RNA-binding protein containing PrLD and RRM domains, and subcellular localization experiments show that EHD6 exhibits a scattered distribution in the cytoplasm, which is caused by PrLD domain-mediated phase separation.
Further yeast two-hybrid sieve library showed that EHD6 could interact with the m6A reader protein YTH07 containing YTH domain, which was subsequently verified by various experiments such as pull-down, BiFC and Co-IP. In vitro and in vivo experiments showed that EHD6 could promote the efficient binding of YTH07 to m6A, and CLIP-seq et al. found that most of the target genes bound to EHD6 were modified by m6A, and about 80% of the target genes bound to YTH07 were also target genes of EHD6. Further studies showed that EHD6 could also promote the phase separation of YTH07, block the translation of the heading inhibitory gene OsCOL4 from mRNA to protein by forming condensates, reduce the protein accumulation of OsCOL4, and then relieve the transcriptional repression of the downstream gene Ehd1, produce more anthocyclins, and promote rice heading. This study not only discovered the phenomenon of efficient binding of m6A by RNA-binding proteins through interaction with the YTH family, revealed the molecular mechanism of m6A inhibition of protein accumulation through phase separation, but also provided genetic resources such as EHD6 and YTH07 for the regulation of rice heading stage.
Dr. Cui Song of Academician Wan Jianmin's research group and Song Peizhe of Professor Jia Guifang's group of Peking University are the co-first authors of this paper, and Academician Wan Jianmin, Professor Zhou Shirong and Professor Jia Guifang are the co-corresponding authors of the paper.
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