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Plos Genentics：拟南芥非光合质体中的脂肪酸合成作用于花粉发育

已有 2763 次阅读 2019-1-18 10:19 |个人分类:每日摘要|系统分类:论文交流

Regulation of pollen lipid body biogenesis by MAP kinases and downstream WRKY transcription factors in Arabidopsis

First author: Yueping Zheng; Affiliations: Zhejiang University (浙江大学): Hangzhou, China

Corresponding author: Shuqun Zhang

Signaling pathways that control the activities in non-photosynthetic plastids, important sites of plant metabolism, are largely unknown. Previously, we demonstrated that WRKY2 and WRKY34 transcription factors play an essential role in pollen development downstream of mitogen-activated protein kinase 3 (MPK3) and MPK6 in Arabidopsis. Here, we report that GLUCOSE-6-PHOSPHATE/PHOSPHATE TRANSLOCATOR 1 (GPT1) is a key target gene of WRKY2/WRKY34. GPT1 transports glucose-6-phosphate (Glc6P) into plastids for starch and/or fatty acid biosynthesis depending on the plant species. Loss of function of WRKY2/WRKY34 results in reduced GPT1 expression, and concomitantly (伴随地), reduced accumulation of lipid bodies in mature pollen, which leads to compromised pollen viability, germination, pollen tube growth, and male transmission in Arabidopsis. Pollen-specific overexpression of GPT1 rescues the pollen defects of wrky2 wrky34 double mutant. Furthermore, gain-of-function activation of MPK3/MPK6 enhances GPT1 expression; whereas GPT1 expression is reduced in mkk4 mkk5double mutant. Together, this study revealed a cytoplasmic/nuclear signaling pathway capable of coordinating the metabolic activities in plastids. High-level expression of GPT1 at late stages of pollen development drives Glc6P from cytosol into plastids, where Glc6P is used for fatty acid biosynthesis, an important step of lipid body biogenesis. The accumulation of lipid bodies during pollen maturation is essential to pollen fitness and successful reproduction.

目前，对于调控植物非光合质体的信号通路还所知甚少，但这些质体是植物代谢的重要位点。作者先前的研究揭示了拟南芥中WRKY2和WRKY34转录因子在花粉发育过程中在丝裂原活化蛋白激酶MPK3和MPK6的下游发挥重要作用。本文，作者报道了葡糖-6-磷酸/磷酸转运体GPT1基因是WRKY2/WRKY34的一个关键靶基因。GPT1将葡糖-6-磷酸Glc6P转运至质体用于淀粉或脂肪酸的生物合成。WRKY2/WRKY34的功能缺失突变体会导致GPT1基因的表达下调，同时会减少成熟花粉中脂质体的积累，进而导致拟南芥的花粉活力、萌发、花粉管生长及雄配子转移受损。花粉特异性过表达GPT1能够拯救wrky2 wrky34双突的表型。综上，本文的研究揭示了一个细胞质/核信号通路能够协调质体中的代谢活性。花粉发育后期高水平的GPT1表达驱动Glc6P由细胞质转运到质体中用于脂肪酸的合成，这是脂质体合成通路上的一个重要步骤。花粉成熟过程中脂质体的积累对于花粉活性和生殖成功是至关重要的。