籽粒大小是影響糧食作物產量的關鍵因素之一。最近，臺灣中央研究院餘淑美團隊及其合作者新發現了一個影響水稻籽粒大小的基因RBG1，能夠調控籽粒和器官發育並增強對非生物脅迫的耐受性。
研究人員從一份T-DNA激活突變體庫中鑑定到一個籽粒變大的突變體材料。經鑑定，包含actin的T-DNA序列插入到基因LOC_Os11g30430（RBG1）的啟動子區域，激活了該基因的表達。進一步研究顯示，RBG1在分生組織和增殖組織中具有優勢表達。異位表達RBG1不僅能夠導致籽粒大小顯著增加，而且還導致根、地上部和穗部等其他主要器官的大小顯著增加。而籽粒尺寸的增加主要是由於細胞數量的增加，而不是細胞體積的增大，這是因為RBG1與已知的參與細胞分裂的微管共定位，RBG1的異位表達促進了細胞分裂。此外，RBG1的異位表達也增加了生長素的積累和敏感性，從而促進了根尤其是冠根的發育。過表達RBG1會上調大量熱激蛋白的表達，提高了植物對高溫、滲透和鹽脅迫的耐受性，並能增強水稻從缺水脅迫環境下的恢復能力。在適當的組成型啟動子GOS2的調控下，RBG1的異位表達能夠提高水稻的收穫指數和產量。
該研究新發現了一個調控水稻籽粒大小的基因RBG1，並揭示了其通過對細胞分裂、生長素和逆境蛋白的誘導作用，調節水稻的產量和抗逆性的功能。
Plant Biotechnology Journal, 07 February 2020
Rice Big Grain 1 promotes cell division to enhance organ development, stress tolerance and grain yield
Author
Shuen‐Fang Lo, Ming‐Lung Cheng, Yue‐Ie Hsing, Yi‐Shih Chen, Kuo‐Wei Lee, Ya‐Fang Hong, Yu Hsiao, An‐Shan Hsiao, Pei‐Jing Chen, Lai‐In Wong, Nan‐Chen Chen, Christophe Reuzeau, Tuan‐Hua David Ho, Su‐May Yu*
*: Academia Sinica; National Chung Hsing University; National Cheng Kung University; National Chung Hsing University, Taiwan, ROC
Abstract
Grain/seed yield and plant stress tolerance are two major traits that determine the yield potential of many crops. In cereals, grain size is one of the key factors affecting grain yield. Here, we identify and characterize a newly‐discovered gene Rice Big Grain 1 (RBG1) that regulates grain and organ development, as well as abiotic stress tolerance. Ectopic expression of RBG1 leads to significant increases in the size not only of grains but also other major organs such as roots, shoots and panicles. Increased grain size is primarily due to elevated cell numbers rather than cell enlargement. RBG1 is preferentially expressed in meristematic and proliferating tissues. Ectopic expression of RBG1 promotes cell division, and RBG1 co‐localizes with microtubules known to be involved in cell division, which may account for the increase in organ size. Ectopic expression of RBG1 also increases auxin accumulation and sensitivity, which facilitates root development, particularly crown roots. Moreover, overexpression of RBG1 upregulated a large number of heat shock proteins, leading to enhanced tolerance to heat, osmotic and salt stresses, as well as rapid recovery from water‐deficit stress. Ectopic expression of RBG1 regulated by a specific constitutive promoter, GOS2, enhanced harvest index and grain yield in rice. Taken together, we have discovered that RBG1 regulates two distinct and important traits in rice, namely grain yield and stress tolerance, via its effects on cell division, auxin and stress protein induction.
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臺灣中央研究院餘淑美團隊揭示水稻糖含量調控機制