The RNA binding protein EHD6 recruits the m6A reader YTH07 and sequesters OsCOL4 mRNA into phase-separated ribonucleoprotein condensates to promote rice flowering

Abstract

N⁶-Methyladenosine (m⁶A) is one of the most abundant modifications of eukaryotic mRNA, but its comprehensive biological functionality remains further exploration. In this study, we identified and characterized a new flowering-promoting gene, EARLY HEADING DATE6 (EHD6), in rice. EHD6 encodes an RNA recognition motif (RRM)-containing RNA binding protein that is localized in the non-membranous cytoplasm ribonucleoprotein (RNP) granules and can bind both m⁶A-modified RNA and unmodified RNA indiscriminately. We found that EHD6 can physically interact with YTH07, a YTH (YT521-B homology) domain-containing m⁶A reader. We showed that their interaction enhances the binding of an m⁶A-modified RNA and triggers relocation of a portion of YTH07 from the cytoplasm into RNP granules through phase-separated condensation. Within these condensates, the mRNA of a rice flowering repressor, CONSTANS-like 4 (OsCOL4), becomes sequestered, leading to a reduction in its protein abundance and thus accelerated flowering through the Early heading date 1 pathway. Taken together, these results not only shed new light on the molecular mechanism of efficient m⁶A recognition by the collaboration between an RNA binding protein and YTH family m⁶A reader, but also uncover the potential for m⁶A-mediated translation regulation through phase-separated ribonucleoprotein condensation in rice.

Keywords: EHD6; N(6)-methyladenosine; YTH domain-containing protein; heading date; m(6)A; phase separation.