Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, SE-90736 Umeå, Sweden.
Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden.
J Exp Bot. 2021 Oct 26;72(20):7107-7118. doi: 10.1093/jxb/erab358.
Adventitious rooting is a de novo organogenesis process that enables plants to propagate clonally and cope with environmental stresses. Adventitious root initiation (ARI) is controlled by interconnected transcriptional and hormonal networks, but there is little knowledge of the genetic and molecular programs orchestrating these networks. Thus, we have applied genome-wide transcriptome profiling to elucidate the transcriptional reprogramming events preceding ARI. These reprogramming events are associated with the down-regulation of cytokinin (CK) signaling and response genes, which could be triggers for ARI. Interestingly, we found that CK free base (iP, tZ, cZ, and DHZ) content declined during ARI, due to down-regulation of de novo CK biosynthesis and up-regulation of CK inactivation pathways. We also found that MYC2-dependent jasmonate (JA) signaling inhibits ARI by down-regulating the expression of the CYTOKININ OXIDASE/DEHYDROGENASE1 (CKX1) gene. We also demonstrated that JA and CK synergistically activate expression of the transcription factor RELATED to APETALA2.6 LIKE (RAP2.6L), and constitutive expression of this transcription factor strongly inhibits ARI. Collectively, our findings reveal that previously unknown genetic interactions between JA and CK play key roles in ARI.
不定根发生是一种新的器官发生过程,使植物能够无性繁殖并应对环境压力。不定根发生(ARI)受相互连接的转录和激素网络控制,但对协调这些网络的遗传和分子程序知之甚少。因此,我们应用全基因组转录组谱分析来阐明 ARI 之前的转录重编程事件。这些重编程事件与细胞分裂素(CK)信号转导和应答基因的下调有关,这可能是 ARI 的触发因素。有趣的是,我们发现 CK 游离碱基(iP、tZ、cZ 和 DHZ)含量在 ARI 期间下降,这是由于 CK 生物合成的下调和 CK 失活途径的上调所致。我们还发现,依赖 MYC2 的茉莉酸(JA)信号通过下调细胞分裂素氧化酶/脱氢酶 1(CKX1)基因的表达抑制 ARI。我们还证明,JA 和 CK 协同激活转录因子 RELATED to APETALA2.6 LIKE(RAP2.6L)的表达,该转录因子的组成性表达强烈抑制 ARI。总之,我们的研究结果表明,JA 和 CK 之间以前未知的遗传相互作用在 ARI 中发挥关键作用。