PCPR5-mediated nucleo-cytoplasmic localization of IAA12 and IAA19 controls lateral root development during abiotic stress

第一作者：Heejae Nam

第一单位：韩国浦项科技大学

通讯作者：Ildoo Hwang

背景回顾：Plasticity of the root system architecture (RSA) is essential in enabling plants to cope with various environmental stresses and is mainly controlled by the phytohormone auxin. Lateral root development is a major determinant of RSA. 

提出问题：Abiotic stresses reduce auxin signaling output, inhibiting lateral root development; however, how abiotic stress translates into a lower auxin signaling output is not fully understood.  

主要发现：Here, we show that the nucleo-cytoplasmic distribution of the negative regulators of auxin signaling AUXIN/INDOLE-3-ACETIC ACID INDUCIBLE 12 (AUX/IAA12 or IAA12) and IAA19 determines lateral root development under various abiotic stress conditions. 

结果1-IAA12/19胞质定位-生长素信号-侧根发育：The cytoplasmic localization of IAA12 and IAA19 in the root elongation zone enforces auxin signaling output, allowing lateral root development.  

结果2-CPR5-IAA12/19胞质易位：Among components of the nuclear pore complex, we show that CONSTITUTIVE EXPRESSOR OF PATHOGENESIS-RELATED GENES 5 (CPR5) selectively mediates the cytoplasmic translocation of IAA12/19. 

结果3-非生物胁迫-CPR5表达-IAA12/19核定位-侧根发育：Under abiotic stress conditions, CPR5 expression is strongly decreased, resulting in the accumulation of nucleus-localized IAA12/19 in the root elongation zone and the suppression of lateral root development, which is reiterated in the cpr5 mutant. 

结论：This study reveals a regulatory mechanism for auxin signaling whereby the spatial distribution of AUX/IAA regulators is critical for lateral root development, especially in fluctuating environmental conditions.

根系结构（RSA）的可塑性对于植物适应不同的环境胁迫是十分重要的，而其主要受到植物激素生长素的控制。侧根的发育是RSA的主要决定因素。非生物胁迫往往会降低生长素的输出，从而抑制侧根的发育；但是，非生物胁迫信号是如何被最终翻译为低水平的生长素信号输出的还不清楚。本文中，作者发现生长素信号转导负调控因子IAA12和IAA19的核质分布决定了其在各种非生物胁迫条件下的侧根发育。根伸长区IAA12和IAA19在胞质的定位增强了生长素信号输出，从而侧根侧根能够正常发育。在细胞核孔复合物的组分中，作者鉴定到了CPR5蛋白能够选择性地介导IAA12/19的胞质易位。在非生物胁迫条件下，CPR5基因的表达大幅度降低，导致根伸长区中IAA12/19在细胞核的积累，从而抑制了侧根的发育，而这些表型在cpr5突变体中同样存在。本文的研究揭示了一个作用于生长素信号转导的调控机制，通过对AUX/IAA蛋白的空间分布，从而介导植物尤其在波动环境条件下的侧根发育。