Wen Zhengyang, Chen Zhifeng, Liu Xinyan, Sun Jingbo, Zhang Feng, Zhang Mengxia, Dong Chunjuan
State Key Laboratory of Vegetable Biobreeding, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
College of Biology and Agricultural Technology, Zunyi Normal College, Zunyi 563006, China.
Antioxidants (Basel). 2023 Jul 19;12(7):1451. doi: 10.3390/antiox12071451.
Adventitious root (AR) formation is a critical process in cutting propagation of horticultural plants. Brassinosteroids (BRs) have been shown to regulate AR formation in several plant species; however, little is known about their exact effects on pepper AR formation, and the downstream signaling of BRs also remains elusive. In this study, we showed that treatment of 24-Epibrassinolide (EBL, an active BR) at the concentrations of 20-100 nM promoted AR formation in pepper (). Furthermore, we investigated the roles of apoplastic reactive oxygen species (ROS), including hydrogen peroxide (HO) and superoxide radical (O), in EBL-promoted AR formation, by using physiological, histochemical, bioinformatic, and biochemical approaches. EBL promoted AR formation by modulating cell-wall-located polyamine oxidase (PAO)-dependent HO production and respiratory burst oxidase homologue (RBOH)-dependent O production, respectively. Screening of and gene families combined with gene expression analysis suggested that EBL-promoted AR formation correlated with the upregulation of , , , and in the AR zone. Transient expression analysis confirmed that CaPAO1 was able to produce HO, and CaRBOH2, CaRBOH5, and CaRBOH6 were capable of producing O. The silencing of , , , and in pepper decreased the ROS accumulation and abolished the EBL-induced AR formation. Overall, these results uncover one of the regulatory pathways for BR-regulated AR formation, and extend our knowledge of the functions of BRs and of the BRs-ROS crosstalk in plant development.
不定根（AR）形成是园艺植物扦插繁殖中的一个关键过程。油菜素甾体类化合物（BRs）已被证明可调节多种植物物种的不定根形成；然而，关于它们对辣椒不定根形成的确切影响知之甚少，并且BRs的下游信号传导也仍然不清楚。在本研究中，我们表明用20 - 100 nM浓度的24 - 表油菜素内酯（EBL，一种活性BR）处理可促进辣椒不定根的形成。此外，我们通过生理、组织化学、生物信息学和生化方法研究了质外体活性氧（ROS），包括过氧化氢（HO）和超氧阴离子自由基（O）在EBL促进不定根形成中的作用。EBL分别通过调节细胞壁定位的多胺氧化酶（PAO）依赖性HO产生和呼吸爆发氧化酶同源物（RBOH）依赖性O产生来促进不定根形成。对 和 基因家族的筛选以及基因表达分析表明，EBL促进的不定根形成与不定根区域中 、 、 和 的上调相关。瞬时表达分析证实CaPAO1能够产生HO，并且CaRBOH2、CaRBOH5和CaRBOH6能够产生O。辣椒中 、 、 和 的沉默降低了ROS积累并消除了EBL诱导的不定根形成。总体而言，这些结果揭示了BR调节不定根形成的调控途径之一，并扩展了我们对BR功能以及植物发育中BR - ROS相互作用的认识。
