Plant Physiol |上海交大左开井团队揭钙蛋白CML38和肽1受体2 PEPR2整合硝酸盐和油菜素内酯信号调节根的生长

植物具有显著的发育可塑性，能够适应土壤低氮等不利的环境条件。油菜素内酯(BRs)在轻度缺氮条件下促进根系对营养物质的觅食，但 BR- 和 氮信号通路在调节根系生长方面的相互作用尚不清楚。在这里，我们证明了钙调蛋白 like-38(CML38) ，一种钙调蛋白样蛋白，特异性地与 PEP1受体2(PEPR2)相互作用，并负向调节拟南芥(Arabidopsis)的根伸长，以应对低硝酸盐拟南芥。外源硝酸盐和 BR 处理诱导了 CML38和 PEPR2的转录。与 Col-0相比，单突变体 cml38、 pepr2和双突变体 cml38pepr2在低硝态氮条件下能促进初生根的生长，产生更多的侧根。这与它们较高的硝酸盐吸收能力和较强的硝酸盐同化基因表达相一致。此外，CML38和 PEPR2还调节与 BR 信号相关的常见下游基因，在 BR 信号转导中发挥积极作用。低氮促进了 BR 信号在过量表达的 Col-0和 CML38- 或 pepr2植株中的传递，而在 CML38和 pepr2突变体中则没有。综上所述，我们的研究结果阐明了 CML38与 PEPR2相互作用的机制，即整合低硝态氮和 BR 信号，协调根系发育，以防止 Arabidopsis 氮资源的迅速耗竭。

Plants exhibit remarkable developmental plasticity, enabling them to adapt to adverse environmental conditions such as low nitrogen (N) in the soil. Brassinosteroids (BRs) promote root foraging for nutrients under mild N deficiency, but the crosstalk between the BR- and N-signaling pathways in the regulation of root growth remains largely unknown. Here, we show that CALMODULIN-LIKE-38 (CML38), a calmodulin-like protein, specifically interacts with the PEP1 RECEPTOR 2 (PEPR2), and negatively regulates root elongation in Arabidopsis (Arabidopsis thaliana) in response to low nitrate. CML38 and PEPR2 are transcriptionally induced by treatments of exogenous nitrate and BR. Compared with Col-0, the single mutants cml38 and pepr2 and the double mutant cml38 pepr2 displayed enhanced primary root growth and produced more lateral roots (LRs) under low nitrate. This is consistent with their higher nitrate absorption abilities, and their stronger expression of nitrate assimilation genes. Furthermore, CML38 and PEPR2 regulate common downstream genes related to BR signaling, and they have positive roles in BR signaling. Low N facilitated BR signal transmission in Col-0 and CML38- or PEPR2-overexpressing plants, but not in the cml38 and pepr2 mutants. Taken together, our results illustrate a mechanism by which CML38 interacts with PEPR2 to integrate low-nitrate and BR signals for coordinating root development to prevent quick depletion of N resources in Arabidopsis.

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