PDF(Pubmed)
Abstract：
Embryogenesis is a critical developmental process that establishes the body organization of higher plants. During this process, the biogenesis of chloroplasts from proplastids is essential. A failure in chloroplast development during embryogenesis can cause morphologically abnormal embryos or embryonic lethality. In this study, we isolated a T-DNA insertion mutant of the Arabidopsis gene EMBRYO DEFECTIVE 2726 (EMB2726). Heterozygous emb2726 seedlings produced about 25% albino seeds with embryos that displayed defects at the 32-cell stage and that arrested development at the late globular stage. EMB2726 protein was localized in chloroplasts and was expressed at all stages of development, such as embryogenesis. Moreover, the two translation elongation factor Ts domains within the protein were critical for its function. Transmission electron microscopy revealed that the cells in emb2726 embryos contained undifferentiated proplastids and that the expression of plastid genome-encoded photosynthesis-related genes was dramatically reduced. Expression studies of DR5:GFP, pDRN:DRN-GFP, and pPIN1:PIN1-GFP reporter lines indicated normal auxin biosynthesis but altered polar auxin transport. The expression of pSHR:SHR-GFP and pSCR:SCR-GFP confirmed that procambium and ground tissue precursors were lacking in emb2726 embryos. The results suggest that EMB2726 plays a critical role during Arabidopsis embryogenesis by affecting chloroplast development, possibly by affecting the translation process in plastids.
摘要：
胚胎发生是建立高等植物身体组织的关键发育过程。在这个过程中,叶绿体的生物发生是必不可少的。胚胎发生过程中叶绿体发育的失败会导致胚胎形态异常或胚胎致死。在这项研究中,我们分离了拟南芥基因胚胎缺陷2726(EMB2726)的T-DNA插入突变体。杂合的emb2726幼苗产生了约25％的白化种子，其胚在32细胞阶段表现出缺陷，并在球形后期阻止了发育。EMB2726蛋白定位于叶绿体中，在发育的各个阶段都有表达，如胚胎发生。此外，蛋白质中的两个翻译延伸因子Ts结构域对其功能至关重要。透射电子显微镜显示，emb2726胚胎中的细胞含有未分化的前质体，质体基因组编码的光合作用相关基因的表达显着降低。DR5:GFP的表达研究,pDRN:DRN-GFP,和pPIN1:PIN1-GFP报道系表明生长素生物合成正常,但改变了极性生长素转运。pSHR:SHR-GFP和pSCR:SCR-GFP的表达证实emb2726胚胎中缺乏原形成层和地面组织前体。结果表明，EMB2726通过影响叶绿体发育在拟南芥胚胎发生中起关键作用，可能是通过影响质体的翻译过程。
