背景:外显子连接复合物(EJC),它包含四个核心组件,真核起始因子4AIII(eIF4AIII),MAGO/NASHI(MAGO),Y14/Tsunagi/RNA结合蛋白8A,和Barentsz/转移淋巴结51,在细胞核和细胞质中形成,在基因表达中起着重要作用。在植物中发现了编码核心EJC成分的基因,包括大米。目前,已经在水稻中证明了MAGO和Y14同源物的功能特征。然而,目前尚不清楚eIF4AIII是否对水稻中的功能性EJC至关重要。
结果:本研究调查了两种DEAD盒RNA解旋酶,与eIF4AIII同源的OsRH2和OsRH34,在米饭里。氨基酸序列分析表明OsRH2和OsRH34具有99%的同一性和100%的相似性,它们的基因表达模式在不同的水稻组织中相似,但幼苗中OsRH2mRNA的水平比OsRH34mRNA的水平高约58倍。从双分子荧光互补结果来看,OsRH2和OsRH34与OsMAGO1和OsY14b物理相互作用,分别,表明OsRH2和OsRH34都是水稻EJC的核心成分。为了研究OsRH2和OsRH34在水稻中的生物学作用,通过RNA干扰产生转基因水稻植株。三个独立的OsRH2和OsRH34双敲低转基因品系的表型包括侏儒症,节点间距离短,生殖延迟,胚胎发育缺陷,种子结实率低。这些表型类似于具有赤霉素相关发育缺陷的突变体。此外,OsRH2和OsRH34双敲除转基因品系表现出未剪接水稻未发育的TAPETUM1mRNA的积累。
结论:水稻含有两个eIF4AIII同源基因,OsRH2和OsRH34。幼苗中OsRH2mRNA的丰度比OsRH34mRNA的丰度高约58倍,表明OsRH2是水稻中主要的eIF4AIII。OsRH2和OsRH34都是EJC的核心部件,参与植物高度的调节,花粉,和水稻的种子发育。
BACKGROUND: The exon junction complex (EJC), which contains four core components, eukaryotic initiation factor 4AIII (eIF4AIII), MAGO/NASHI (MAGO), Y14/Tsunagi/RNA-binding protein 8A, and Barentsz/Metastatic lymph node 51, is formed in both nucleus and cytoplasm, and plays important roles in gene expression. Genes encoding core EJC components have been found in plants, including rice. Currently, the functional characterizations of MAGO and Y14 homologs have been demonstrated in rice. However, it is still unknown whether eIF4AIII is essential for the functional EJC in rice.
RESULTS: This study investigated two DEAD box RNA helicases, OsRH2 and OsRH34, which are homologous to eIF4AIII, in rice. Amino acid sequence analysis indicated that OsRH2 and OsRH34 had 99 % identity and 100 % similarity, and their gene expression patterns were similar in various rice tissues, but the level of OsRH2 mRNA was about 58-fold higher than that of OsRH34 mRNA in seedlings. From bimolecular fluorescence complementation results, OsRH2 and OsRH34 interacted physically with OsMAGO1 and OsY14b, respectively, which indicated that both of OsRH2 and OsRH34 were core components of the EJC in rice. To study the biological roles of OsRH2 and OsRH34 in rice, transgenic rice plants were generated by RNA interference. The phenotypes of three independent OsRH2 and OsRH34 double-knockdown transgenic lines included dwarfism, a short internode distance, reproductive delay, defective embryonic development, and a low seed setting rate. These phenotypes resembled those of mutants with gibberellin-related developmental defects. In addition, the OsRH2 and OsRH34 double-knockdown transgenic lines exhibited the accumulation of unspliced rice UNDEVELOPED TAPETUM 1 mRNA.
CONCLUSIONS: Rice contains two eIF4AIII paralogous genes, OsRH2 and OsRH34. The abundance of OsRH2 mRNA was about 58-fold higher than that of OsRH34 mRNA in seedlings, suggesting that the OsRH2 is major eIF4AIII in rice. Both OsRH2 and OsRH34 are core components of the EJC, and participate in regulating of plant height, pollen, and seed development in rice.