Mutation of an Arabidopsis NatB N-Alpha-Terminal Acetylation Complex Component Causes Pleiotropic Developmental Defects

N-α-terminal acetylation is one of the most common, but least understood modifications of eukaryotic proteins. Although a high degree of conservation exists between the N-α-terminal acetylomes of plants and animals, very little information is available on this modification in plants. In yeast and humans, N-α-acetyltransferase complexes include a single catalytic subunit and one or two auxiliary subunits. Here, we report the positional cloning of TRANSCURVATA2 (TCU2), which encodes the auxiliary subunit of the NatB N-α-acetyltransferase complex in Arabidopsis. The phenotypes of loss-of-function tcu2 alleles indicate that NatB complex activity is required for flowering time regulation and for leaf, inflorescence, flower, fruit and embryonic development. In double mutants, tcu2 alleles synergistically interact with alleles of ARGONAUTE10, which encodes a component of the microRNA machinery. In summary, NatB-mediated N-α-terminal acetylation of proteins is pleiotropically required for Arabidopsis development and seems to be functionally related to the microRNA pathway.

Nα末端乙酰化（N-α-terminal acetylation）是真核蛋白质（eukaryotic proteins）最普遍却最缺乏研究的修饰方式之一。尽管动植物的Nα末端乙酰化组（N-α-terminal acetylomes）之间存在高度保守性，但目前关于植物中该修饰的相关信息仍极为匮乏。在酵母与人类体内，Nα乙酰转移酶复合物（N-α-acetyltransferase complexes）包含一个催化亚基与一至两个辅助亚基。本研究报道了拟南芥（Arabidopsis）中NatB型Nα乙酰转移酶复合物辅助亚基的编码基因TRANSCURVATA2（TCU2）的图位克隆（positional cloning）结果。功能缺失型tcu2等位基因的表型分析显示，NatB复合物的活性对于开花时间调控，以及叶片、花序、花、果实与胚胎发育均不可或缺。在双突变体中，tcu2等位基因与编码微RNA（microRNA）通路组分的ARGONAUTE10等位基因存在协同互作关系。综上，NatB介导的蛋白质Nα末端乙酰化对拟南芥发育具有多效性必需性，且其功能似乎与微RNA途径密切相关。