Al-Mamun Mahamud Hossain, Cazzonelli Christopher Ian, Krishna Priti
School of Science, Western Sydney University, Richmond, NSW, Australia.
Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, Australia.
Front Plant Sci. 2024 May 8;15:1387321. doi: 10.3389/fpls.2024.1387321. eCollection 2024.
Plants modify their root system architecture (RSA) in response to nitrogen (N) deficiency. The plant steroidal hormone, brassinosteroid (BR), plays important roles in root growth and development. This study demonstrates that optimal levels of exogenous BR impact significant increases in lateral root length and numbers in seedlings under mild N-deficient conditions as compared to untreated seedlings. The impact of BR on RSA was stronger under mild N deficiency than under N-sufficient conditions. The BR effects on RSA were mimicked in dominant mutants of BZR1 and BES1 ( and ) transcription factors, while the RSA was highly reduced in the BR-insensitive mutant , confirming that BR signaling is essential for the development of RSA under both N-sufficient and N-deficient conditions. Exogenous BR and constitutive activity of BZR1 and BES1 in dominant mutants led to enhanced root meristem, meristematic cell number, and cortical cell length. Under mild N deficiency, displayed higher fresh and dry shoot weights, chlorophyll content, and N levels in the shoot, as compared to the wild type. These results indicate that BR modulates RSA under both N-sufficient and N-deficient conditions via the transcription factors BES1/BZR1 module and confers tolerance to N deficiency.
植物会根据氮（N）缺乏情况来改变其根系结构（RSA）。植物甾体激素油菜素内酯（BR）在根系生长和发育中发挥着重要作用。本研究表明，与未处理的幼苗相比，在轻度缺氮条件下，最佳水平的外源BR能显著增加幼苗侧根的长度和数量。在轻度缺氮条件下，BR对RSA的影响比在氮充足条件下更强。BZR1和BES1转录因子的显性突变体模拟了BR对RSA的影响，而在BR不敏感突变体中RSA则大幅降低，这证实了BR信号传导对于氮充足和缺氮条件下RSA的发育都是必不可少的。外源BR以及显性突变体中BZR1和BES1的组成型活性导致根分生组织、分生细胞数量和皮层细胞长度增加。在轻度缺氮条件下，与野生型相比，[此处原文可能缺失具体突变体名称]表现出更高的地上部鲜重和干重、叶绿素含量以及地上部氮含量。这些结果表明，BR通过转录因子BES1/BZR1模块在氮充足和缺氮条件下调节RSA，并赋予对缺氮的耐受性。
