Key Laboratory of Plant Nutrition and Fertilizer, Ministry of Agriculture, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 10081, China.
Hebei Wotu Seed Co. Ltd., Handan 057550, China.
Plant Cell. 2022 Aug 25;34(9):3319-3338. doi: 10.1093/plcell/koac161.
Phosphate (Pi) limitation represents a primary constraint on crop production. To better cope with Pi deficiency stress, plants have evolved multiple adaptive mechanisms for phosphorus acquisition and utilization, including the alteration of growth and the activation of Pi starvation signaling. However, how these strategies are coordinated remains largely unknown. Here, we found that the alternative splicing (AS) of REGULATOR OF LEAF INCLINATION 1 (RLI1) in rice (Oryza sativa) produces two protein isoforms: RLI1a, containing MYB DNA binding domain and RLI1b, containing both MYB and coiled-coil (CC) domains. The absence of a CC domain in RLI1a enables it to activate broader target genes than RLI1b. RLI1a, but not RLI1b, regulates both brassinolide (BL) biosynthesis and signaling by directly activating BL-biosynthesis and signaling genes. Both RLI1a and RLI1b modulate Pi starvation signaling. RLI1 and PHOSPHATE STARVATION RESPONSE 2 function redundantly to regulate Pi starvation signaling and growth in response to Pi deficiency. Furthermore, the AS of RLI1-related genes to produce two isoforms for growth and Pi signaling is widely present in both dicots and monocots. Together, these findings indicate that the AS of RLI1 is an important and functionally conserved strategy to orchestrate Pi starvation signaling and growth to help plants adapt to Pi-limitation stress.
磷酸盐（Pi）限制是作物生产的主要限制因素。为了更好地应对 Pi 缺乏胁迫，植物进化出了多种获取和利用磷的适应机制，包括生长的改变和 Pi 饥饿信号的激活。然而，这些策略是如何协调的仍然很大程度上是未知的。在这里，我们发现水稻（Oryza sativa）中 REGULATOR OF LEAF INCLINATION 1（RLI1）的可变剪接（AS）产生两种蛋白质异构体：RLI1a，含有 MYB DNA 结合域；RLI1b，含有 MYB 和卷曲螺旋（CC）域。RLI1a 中 CC 结构域的缺失使其能够激活比 RLI1b 更广泛的靶基因。RLI1a 而非 RLI1b 通过直接激活 BL 生物合成和信号基因来调节油菜素内酯（BL）的生物合成和信号。RLI1a 和 RLI1b 均调节 Pi 饥饿信号。RLI1 和 PHOSPHATE STARVATION RESPONSE 2 冗余地调节 Pi 饥饿信号和对 Pi 缺乏的生长反应。此外，RLI1 相关基因的 AS 产生两种用于生长和 Pi 信号的异构体，在双子叶植物和单子叶植物中广泛存在。总之，这些发现表明 RLI1 的 AS 是协调 Pi 饥饿信号和生长以帮助植物适应 Pi 限制胁迫的重要且功能保守的策略。
