State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
Department of Plant Pathology, Ohio State University, Columbus, OH, 43210, USA.
New Phytol. 2020 Jan;225(1):413-429. doi: 10.1111/nph.16156. Epub 2019 Sep 30.
Protein arginine methyltransferases (PRMTs) regulate many physiological processes, including autophagy. However, the direct roles of the various PRMTs during autophagosome formation remain unclear. Here, we characterised the function of MoHMT1 in the rice blast fungus, Magnaporthe oryzae. Knockout of MoHMT1 results in inhibited growth and a decreased ability to cause disease lesions on rice seedlings. MoHMT1 catalyses the di-methylation of arginine 247, 251, 261 and 271 residues of MoSNP1, a U1 small nuclear ribonucleoprotein (snRNP) component, likely in a manner dependent on direct interaction. RNA-seq analysis revealed that alternative splicing of pre-mRNAs of 558 genes, including the autophagy-related (ATG) gene MoATG4, was altered in MoHMT1 deletion mutants, compared with wild-type strains under normal growth conditions. During light exposure or nitrogen starvation, MoHMT1 localises to autophagosomes and MoHMT1 mutants display defects in autophagy induction. Under nitrogen starvation, six additional MoATG genes were identified with retained introns in their mRNA transcripts, corresponding with a significant reduction in transcripts of intron-spliced isoforms in the MoHMT1 mutant strain. Our study shows that arginine methylation plays an essential role in accurate pre-mRNA splicing necessary for a range of developmental processes, including autophagosome formation.
蛋白质精氨酸甲基转移酶（PRMTs）调节许多生理过程，包括自噬。然而，各种 PRMTs 在自噬体形成过程中的直接作用尚不清楚。在这里，我们研究了水稻纹枯病菌（Magnaporthe oryzae）中 MoHMT1 的功能。MoHMT1 的敲除导致生长受到抑制，在水稻幼苗上引起病斑的能力降低。MoHMT1 催化 U1 小核核糖核蛋白（snRNP）成分 MoSNP1 中精氨酸 247、251、261 和 271 残基的二甲基化，可能依赖于直接相互作用。RNA-seq 分析显示，在正常生长条件下，与野生型菌株相比，MoHMT1 缺失突变体中包括自噬相关（ATG）基因 MoATG4 在内的 558 个基因的前体 mRNA 的选择性剪接发生改变。在光照或氮饥饿条件下，MoHMT1 定位于自噬体中，MoHMT1 突变体在自噬诱导中存在缺陷。在氮饥饿条件下，在 MoHMT1 突变体菌株中，发现了另外六个具有保留内含子的 MoATG 基因，这与内含子剪接同工型的转录物显著减少相对应。我们的研究表明，精氨酸甲基化在包括自噬体形成在内的一系列发育过程中，对于准确的前体 mRNA 剪接是必不可少的。
