National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, 430070, China.
J Integr Plant Biol. 2013 Nov;55(11):1104-18. doi: 10.1111/jipb.12102. Epub 2013 Oct 17.
tRNase Z (TRZ) is a ubiquitous endonuclease that removes the 3'-trailer from precursor tRNAs during maturation. In yeast and animals, TRZ regulates the cell cycle via its (t)RNA processing activity; however, its physiological function in higher plants has not been well characterized. This study describes the identification of a rice (Oryza sativa) TRZ2 mutant; plants homozygous for the osatrz2 mutation were albinos with deficient chlorophyll content. A microscopic analysis of the mutant plants revealed that the transition of proplastids to chloroplasts was arrested at an early stage, and the number and size of the plastids in callus cells was substantially decreased. A genetic complementation test and an RNA interference analysis confirmed that disruption of OsaTRZ2 was responsible for the mutant phenotype. OsaTRZ2 is expressed in all rice tissues, but is preferentially expressed in leaves, sheathes, and calli. OsaTRZ2 was subcellularly localized in chloroplasts, and displayed tRNA 3'-end processing activity in both in vitro and in vivo assays. In the osatrz2 mutants, transcription of plastid-encoded and nucleus-encoded RNA polymerases was severely reduced and moderately increased, respectively. These results suggest that the tRNA 3' processing activity of OsaTRZ2 contributes to chloroplast biogenesis.
tRNase Z（TRZ）是一种普遍存在的内切核酸酶，可在成熟过程中从前体 tRNA 中去除 3'-trailer。在酵母和动物中，TRZ 通过其（t）RNA 加工活性来调节细胞周期；然而，其在高等植物中的生理功能尚未得到很好的表征。本研究描述了一种水稻（Oryza sativa）TRZ2 突变体的鉴定；该突变体的纯合子植株是白化体，叶绿素含量不足。对突变体植株的显微镜分析表明，原质体向叶绿体的转变在早期被阻断，愈伤组织细胞中的质体数量和大小显著减少。遗传互补测试和 RNA 干扰分析证实，OsaTRZ2 的破坏是导致突变表型的原因。OsaTRZ2 在所有水稻组织中表达，但在叶片、叶鞘和愈伤组织中优先表达。OsaTRZ2 亚细胞定位于叶绿体，并在体外和体内测定中显示出 tRNA 3'-末端加工活性。在 osatrz2 突变体中，质体编码和核编码 RNA 聚合酶的转录分别严重减少和适度增加。这些结果表明，OsaTRZ2 的 tRNA 3' 加工活性有助于叶绿体的发生。
