RNA化学修饰m^(6)A在植物中的研究进展

RNA chemical modification of mA in plants

N^(6)-甲基腺嘌呤(N^(6)-methyladenosine,m^(6)A)是真核生物mRNA中丰度最高的甲基化修饰形式.m^(6)A修饰是由m^(6)A甲基转移酶复合物催化形成,并由去甲基化酶脱去甲基修饰,而m^(6)A修饰的生物学功能则是由结合蛋白进行调控.随着m^(6)A检测和测序技术的发展,多种m^(6)A修饰相关蛋白在植物中鉴定出来,其调控的生物学功能越来越受到人们的关注.本文针对植物m^(6)A修饰相关调控蛋白及其功能、m^(6)A修饰位置分布及基序特征和m^(6)A调控的分子机制综述研究进展,展望m^(6)A在植物中的研究重点和方向.

N^(6)-methyladenosine(m^(6)A) is the most prevalent methylation modification form of eukaryotic messenger RNAs(mRNA).In plants, m^(6)A participates in a variety of biological processes by affecting mRNA alternative polyadenylation, stability,and translation. In existing research, the absence of some methyltransferase complexes, such as methyltransferase A(MTA), methyltransferase B(MTB), FKBP12 interacting protein(FIP37), and virilizer(VIR), in plants causes embryonic lethality. Lowering gene expression levels of different methyltransferase components will cause severely hindered growth and development, such as growth retardation, over-proliferation of shoot apical meristem, aberrant gravity response,abnormal vascular tissue development, etc. Loss of demethylase Alk B homolog 10 B(ALKBH10 B) increases m^(6)A modification levels of FLOWERING LOCUS T(FT), SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 3(SPL3),and SPL9, lowering their stability, which leads to delayed flowering. The absence of Alk B homolog 9 B(ALKBH9 B) can increase the genomic m^(6)A modification level of the alfalfa mosaic virus(AMV), weakening its infection capacity to plants.RNA binding proteins are mainly proteins with the YTH-domain. The evolutionarily conserved c-terminal region(ECT)represents main RNA binding proteins in plants. ECT2, ECT3, and ECT4, three kinds of ECTs, affect trichome branch numbers, precise leaf formation timing, and leaf morphology. Furthermore, the longer isoform of CLEAVAGE AND POLYADENYLATION SPECIFICITY FACTOR 30(CPSF30-L) which has mRNA binding function influences processes of polyadenylation site selection and phase separation. In addition to these features, these binding proteins are quite likely to be involved in plant response processes to adversity stress. Through the comprehensive analysis of existing studies, we considered that m^(6)A is mainly enriched in the 3′ untranslated regions(3′UTR) region nearby the stop codon of plant mRNAs. As for the m^(6)A modification enriched in the 5′ untranslated regions(5′UTR) region may be relevant to the higher abundance of chloroplast-related genes. The whole plant m^(6)A-seq results show that RR[A]CH is a main m^(6)A motif of plants. Sequencing of m^(6)A at specific tissue sites or the sequence recognized by the binding protein indicated that UGU[A]Y is a plant-specific motif. As for the divergences in existing research about how m^(6)A influences plant mRNA stability, we supposed that the existence of m^(6)A is positively correlated with mRNA stability. However, there would be a negative correlation between m^(6)A level and mRNA stability when m^(6)A exists. In this article, we reviewed the research progress of plant m^(6)A on three aspects, including m^(6)A modification-related regulatory proteins and their functions, m^(6)A position distribution and its motif characteristics, and the molecular mechanism of m^(6)A regulation. Finally, we summarized the high-valued research emphasis and directions of m^(6)A in plants.