Auxin abolishes SHI‐RELATED SEQUENCE5‐mediated inhibition of lateral root development in Arabidopsis

First author: Ting‐Ting Yuan; Affiliations: Wuhan University (武汉大学): Wuhan, China

Corresponding author: Ying‐Tang Lu

Lateral roots (LRs), which form in the plant post‐embryonically, determine the architecture of the root system. While negative regulatory factors that inhibit LR formation and are counteracted by auxin exist in the pericycle, these factors have not been characterized. Here, we report that SHI‐RELATED SEQUENCE5 (SRS5) is an intrinsic negative regulator of LR formation and that auxin signaling abolishes this inhibitory effect of SRS5. Whereas LR primordia (LRPs) and LRs were fewer and less dense in SRS5ox and Pro35S:SRS5‐GFP plants than in the wild type, they were more abundant and denser in the srs5‐2 loss‐of‐function mutant. SRS5 inhibited LR formation by directly downregulating the expression of LATERAL ORGAN BOUNDARIES‐DOMAIN 16 (LBD16) and LBD29. Auxin repressed SRS5 expression. Auxin‐mediated repression of SRS5 expression was not observed in the arf7‐1 arf19‐1 double mutant, likely because ARF7 and ARF19 bind to the promoter of SRS5 and inhibit its expression in response to auxin. Taken together, our data reveal that SRS5 negatively regulates LR formation by repressing the expression of LBD16 and LBD29 and that auxin releases this inhibitory effect through ARF7 and ARF19.

侧根形成于植物胚胎发生后，决定了植物的根系统结构。植物中柱鞘存在生长素的情况下，抑制侧根形成的某些负调控因子的作用会被抵。本文中，作者报道了SRS5是侧根形成的固有负调控因子，而生长素信号能够废除该基因对于侧根形成的抑制效应。SRS5ox和Pro35S:SRS5‐GFP植株的侧根原基和侧根都要比野生型要少，密度也要低的多，而在srs5‐2功能缺失突变体中侧根就要更加密集。SRS5通过直接下调LBD16和LBD29基因的表达来抑制侧根的形成。生长素能够抑制SRS5基因的表达。作者在arf7‐1 arf19‐1双突变体中并未观察到生长素介导的SRS5基因表达抑制，说明很有可能ARF7和ARF19在响应生长素的情况下，通过结合到SRS5基因的启动子抑制其表达。综上，本文的研究揭示了SRS5通过抑制LBD16和LBD29基因的表达来抑制侧根的形成，而生长素则通过ARF7和ARF19来解除这种抑制效果。

通讯：吕应堂  (http://www.bio.whu.edu.cn/info/1191/4303.htm)

个人简介：1978-1982年，武汉大学，学士；1982-1984年，中科院北京遗传所，硕士；1986-1991年，夏威夷大学，博士；1986-1996，美国加州大学伯克利分校，博士后。

研究方向：活性氧、一氧化氮与植物激素如何协调调控植物应答生物及非生物逆境胁迫的分子及细胞学机制。

doi: https://doi.org/10.1111/nph.16115

Journal: New Phytologist

Published date: August 12, 2019