在高等植物中,精子細胞向胚囊的成功傳遞是由花粉管的生長介導的。因此,深入解析作物花粉萌發和花粉管生長的分子機制至關重要。
研究人員通過對水稻花粉特異基因突變體的篩選,篩選到一個水稻花粉萌發調控因子T-DNA插入突變體GORI(Germinating modulator of rice pollen),該突變體表現出野生型與雜合子1:1的分離比。GORI基因編碼一個7-WD40基序蛋白,與擬南芥中的JINGUBANG/REN4同源。GORI基因在水稻花粉中特異表達,其蛋白定位於細胞核、胞漿和質膜。此外,通過CRISPR-Cas9創造的純合突變體gori-2明顯表現出雄性不育且花粉管萌發和伸長受到破壞的表型。此外,gori-2萌發花粉管的肌動蛋白細絲也是減少的,果膠分布也發生了改變。轉錄組分析結果表明,與野生型相比,gori-2中有852個花粉特異基因表達下調,這些基因與細胞壁修飾和網狀蛋白外殼組裝密切相關。這也揭示出Gori在形成介導花粉管生長的內吞/胞吞複合體中起關鍵作用。
The Plant Journal, 21 December 2020
GORI encoding the WD40 domain protein is required for pollen tube germination and elongation in rice
Author
Yu‐Jin Kim, Myung‐Hee Kim, Woo‐Jong Hong, Sunok Moon, Eui‐Jung Kim, Jeniffer Silva, Jinwon Lee, Sangho Lee, Sun Tae Kim, Soon Ki Park, Ki‐Hong Jung*
*: Graduate School of Biotechnology & Crop Biotech Institute, Kyung Hee University, Korea
Abstract
Successful sperm cell delivery to the embryo sac is mediated by pollen tube growth in higher plants. The molecular mechanisms underlying pollen germination and tube growth in crop plants remain highly unclear, although these mechanisms are crucial to plant reproduction and seed formation. By screening pollen‐specific gene mutants in rice (Oryza sativa), we identified a T‐DNA insertional mutant of Germinating modulator of rice pollen (GORI) that showed one‐to‐one segregation ratio for wild type (WT) to heterozygotes. GORI encodes a seven‐WD40 motif protein that is homologous to JINGUBANG/REN4 in Arabidopsis. GORI is specifically expressed in rice pollen, and its protein is localized in the nucleus, cytosol, and plasma membrane. Furthermore, a homozygous mutant, gori‐2, created through CRISPR-Cas9 clearly exhibited male sterility with disruption of pollen tube germination and elongation. The germinated pollen tube of gori‐2 exhibited decreased actin filament and altered pectin distribution. Transcriptome analysis revealed that 852 pollen‐specific genes were down regulated in gori‐2 compared with the WT, and gene ontology enrichment analysis indicated that these genes are strongly associated with cell wall modification and clathrin coat assembly. Based on the molecular features of GORI, phenotypical observation of the gori mutant, and its interaction with endocytic proteins and Rac GTPase (ROP), we propose that GORI plays key roles in forming endo/exocytosis complexes that could mediate pollen tube growth in rice.
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