Hsieh Kun-Ting, Chen Yi-Ting, Hu Ting-Jen, Lin Shih-Min, Hsieh Chih-Hung, Liu Su-Hui, Shiue Shiau-Yu, Lo Shuen-Fang, Wang I-Wen, Tseng Ching-Shan, Chen Liang-Jwu
Institute of Molecular Biology, National Chung Hsing University, Taichung, 40227, Taiwan.
Biotechnology Center, National Chung Hsing University, Taichung, 40227, Taiwan.
Rice (N Y). 2021 Jul 28;14(1):70. doi: 10.1186/s12284-021-00499-4.
GA 2-oxidases (GA2oxs) are involved in regulating GA homeostasis in plants by inactivating bioactive GAs through 2β-hydroxylation. Rice GA2oxs are encoded by a family of 10 genes; some of them have been characterized, but no comprehensive comparisons for all these genes have been conducted.
Rice plants with nine functional GA2oxs were demonstrated in the present study, and these genes not only were differentially expressed but also revealed various capabilities for GA deactivation based on their height-reducing effects in transgenic plants. Compared to that of wild-type plants, the relative plant height (RPH) of transgenic plants was scored to estimate their reducing effects, and 8.3% to 59.5% RPH was observed. Phylogenetic analysis of class I GA2ox genes revealed two functionally distinct clades in the Poaceae. The OsGA2ox3, 4, and 8 genes belonging to clade A showed the most severe effect (8.3% to 8.7% RPH) on plant height reduction, whereas the OsGA2ox7 gene belonging to clade B showed the least severe effect (59.5% RPH). The clade A OsGA2ox3 gene contained two conserved C186/C194 amino acids that were crucial for enzymatic activity. In the present study, these amino acids were replaced with OsGA2ox7-conserved arginine (C186R) and proline (C194P), respectively, or simultaneously (C186R/C194P) to demonstrate their importance in planta. Another two amino acids, Q220 and Y274, conserved in OsGA2ox3 were substituted with glutamic acid (E) and phenylalanine (F), respectively, or simultaneously to show their significance in planta. In addition, through sequence divergence, RNA expression profile and GA deactivation capability analyses, we proposed that OsGA2ox1, OsGA2ox3 and OsGA2ox6 function as the predominant paralogs in each of their respective classes.
This study demonstrates rice has nine functional GA2oxs and the class I GA2ox genes are divided into two functionally distinct clades. Among them, the OsGA2ox7 of clade B is a functional attenuated gene and the OsGA2ox1, OsGA2ox3 and OsGA2ox6 are the three predominant paralogs in the family.
GA 2-氧化酶（GA2oxs）通过2β-羟基化使生物活性赤霉素失活，从而参与植物体内赤霉素稳态的调节。水稻GA2oxs由一个包含10个基因的家族编码；其中一些基因已被鉴定，但尚未对所有这些基因进行全面比较。
本研究证实了水稻中有9个具有功能的GA2oxs基因，这些基因不仅表达存在差异，而且根据它们在转基因植物中的矮化效应显示出不同的赤霉素失活能力。与野生型植物相比，对转基因植物的相对株高（RPH）进行评分以评估其矮化效应，观察到RPH为8.3%至59.5%。对I类GA2ox基因的系统发育分析揭示了禾本科中两个功能不同的进化枝。属于进化枝A的OsGA2ox3、4和8基因对株高降低的影响最为显著（RPH为8.3%至8.7%），而属于进化枝B的OsGA2ox7基因的影响最小（RPH为59.5%）。进化枝A的OsGA2ox3基因包含两个保守的C186/C194氨基酸，它们对酶活性至关重要。在本研究中，分别将这些氨基酸替换为OsGA2ox7保守的精氨酸（C186R）和脯氨酸（C194P），或同时替换（C_{186}R/C_{194}P），以证明它们在植物体内的重要性。OsGA2ox3中另外两个保守的氨基酸Q220和Y274分别或同时被谷氨酸（E）和苯丙氨酸（F）取代，以显示它们在植物体内的重要性。此外，通过序列差异、RNA表达谱和赤霉素失活能力分析，我们提出OsGA2ox1、OsGA2ox3和OsGA2ox6在各自的类别中起主要旁系同源基因的作用。
本研究表明水稻有9个具有功能的GA2oxs基因，I类GA2ox基因分为两个功能不同的进化枝。其中，进化枝B的OsGA2ox7是一个功能减弱的基因，而OsGA2ox1、OsGA2ox3和OsGA2ox6是该家族中的三个主要旁系同源基因。
