Hu Yilong, Zhou Limeng, Yang Yuhua, Zhang Wenbin, Chen Zhonghui, Li Xiaoming, Qian Qian, Kong Fanjiang, Li Yuge, Liu Xu, Hou Xingliang
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 Chinese Academy of Sciences, Beijing 100049, China.
Plant Physiol. 2021 Apr 23;185(4):1697-1707. doi: 10.1093/plphys/kiaa114.
Seed storage protein (SSP) acts as one of the main components of seed storage reserves, of which accumulation is tightly mediated by a sophisticated regulatory network. However, whether and how gibberellin (GA) signaling is involved in this important biological event is not fully understood. Here, we show that SSP content in Arabidopsis (Arabidopsis thaliana) is significantly reduced by GA and increased in the GA biosynthesis triple mutant ga3ox1/3/4. Further investigation shows that the DELLA protein RGA-LIKE3 (RGL3), a negative regulator of GA signaling, is important for SSP accumulation. In rgl3 and 35S:RGL3-HA, the expression of SSP genes is down- and upregulated, respectively, compared with that in the wild-type. RGL3 interacts with ABSCISIC ACID INSENSITIVE3 (ABI3), a critical transcription factor for seed developmental processes governing SSP accumulation, both in vivo and in vitro, thus greatly promoting the transcriptional activating ability of ABI3 on SSP genes. In addition, genetic evidence shows that RGL3 and ABI3 regulate SSP accumulation in an interdependent manner. Therefore, we reveal a function of RGL3, a little studied DELLA member, as a coactivator of ABI3 to promote SSP biosynthesis during seed maturation stage. This finding advances the understanding of mechanisms in GA-mediated seed storage reserve accumulation.
种子贮藏蛋白（SSP）是种子贮藏物质的主要成分之一，其积累受到复杂调控网络的严格介导。然而，赤霉素（GA）信号是否以及如何参与这一重要生物学事件尚未完全清楚。在此，我们表明拟南芥中GA会显著降低SSP含量，而在GA生物合成三突变体ga3ox1/3/4中SSP含量则增加。进一步研究表明，GA信号的负调控因子DELLA蛋白RGA-LIKE3（RGL3）对SSP积累很重要。与野生型相比，在rgl3和35S:RGL3-HA中，SSP基因的表达分别下调和上调。RGL3在体内和体外均与ABSCISIC ACID INSENSITIVE3（ABI3）相互作用，ABI3是控制SSP积累的种子发育过程的关键转录因子，从而极大地促进了ABI3对SSP基因的转录激活能力。此外，遗传学证据表明RGL3和ABI3以相互依赖的方式调节SSP积累。因此，我们揭示了RGL3（一个研究较少的DELLA成员）作为ABI3的共激活因子在种子成熟阶段促进SSP生物合成的功能。这一发现推进了对GA介导的种子贮藏物质积累机制的理解。
