Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement & Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Innovative Academy of Seed Design, Chinese Academy of Sciences, Guangzhou, 510650, China.
University of the Chinese Academy of Sciences, Beijing, 100049, China.
New Phytol. 2021 Jul;231(1):137-151. doi: 10.1111/nph.17314. Epub 2021 Mar 30.
The phytohormone gibberellin (GA) is critical for anther development. RGA, a member of the DELLA family of proteins that are central GA signalling repressors, is a key regulator of male fertility in plants. However, the downstream genes in GA-RGA-mediated anther development remain to be characterised. We identified RGA Target 1 (RGAT1), a novel Arabidopsis gene, that functions as an important RGA-regulated target in pollen development. RGAT1 is predominantly expressed in the tapetum and microspores during anther stages 8-11, and can be directly activated by RGA and suppressed by GA in inflorescence apices. Both loss of function and gain of function of RGAT1 led to abnormal tapetum development, resulting in abortive pollen and short siliques. In RGAT1-knockdown and overexpression lines, pollen abortion occurred at stage 10. Loss of RGAT1 function induced the premature degeneration of tapetal cells with defective ER-derived tapetosomes, while RGAT1 overexpression delayed tapetum degeneration. TUNEL assay confirmed that RGAT1 participates in timely tapetal programmed cell death. Moreover, reducing RGAT1 expression partially rescued the tapetal developmental defects in GA-deficient ga1-3 mutant. Our findings revealed that RGAT1 is a direct target of RGA and plays an essential role in GA-mediated tapetum and pollen development.
植物激素赤霉素（GA）对花粉囊的发育至关重要。RGA 是 DELLA 家族蛋白的成员，是植物中 GA 信号转导的主要抑制剂，是雄性育性的关键调节剂。然而，GA-RGA 介导的花粉囊发育的下游基因仍有待鉴定。我们鉴定了 RGA Target 1（RGAT1），这是一个新的拟南芥基因，作为花粉发育中 RGA 调节的重要靶标。RGAT1 在花粉囊发育的 8-11 期主要在绒毡层和小孢子中表达，并且可以被 RGA 直接激活，在花序顶端被 GA 抑制。RGAT1 的功能丧失和获得都导致了绒毡层发育异常，导致花粉败育和短蒴果。在 RGAT1 敲低和过表达系中，花粉败育发生在 10 期。RGAT1 功能丧失导致绒毡层细胞过早退化，内质网衍生的绒毡体有缺陷，而 RGAT1 过表达则延迟了绒毡层的退化。TUNEL 检测证实 RGAT1 参与了绒毡层的程序性细胞死亡。此外，降低 RGAT1 的表达部分挽救了 GA 缺失的 ga1-3 突变体中绒毡层发育的缺陷。我们的研究结果表明，RGAT1 是 RGA 的直接靶标，在 GA 介导的绒毡层和花粉发育中起重要作用。
