Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore.
Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore.
J Exp Bot. 2023 Jun 27;74(12):3560-3578. doi: 10.1093/jxb/erad088.
Plants respond to vegetative shade with developmental and physiological changes that are collectively known as shade avoidance syndrome (SAS). Although LONG HYPOCOTYL IN FAR-RED 1 (HFR1) is known to be a negative regulator of SAS by forming heterodimers with other basic helix-loop-helix (bHLH) transcription factors to inhibit them, its function in genome-wide transcriptional regulation has not been fully elucidated. Here, we performed RNA-sequencing analyses of Arabidopsis thaliana hfr1-5 mutant and HFR1 overexpression line [HFR1(ΔN)-OE] to comprehensively identify HFR1-regulated genes at different time points of shade treatment. We found that HFR1 mediates the trade-off between shade-induced growth and shade-repressed defence, by regulating the expression of relevant genes in the shade. Genes involved in promoting growth, such as auxin biosynthesis, transport, signalling and response were induced by shade but suppressed by HFR1 under both short and long durations of shade. Likewise, most ethylene-related genes were shade-induced and HFR1-repressed. However, shade suppressed defence-related genes, while HFR1 induced their expression, especially under long durations of shade treatment. We demonstrated that HFR1 confers increased resistance to bacterial infection under shade.
植物通过发育和生理变化来响应营养遮荫，这些变化统称为避荫综合征（SAS）。尽管 LONG HYPOCOTYL IN FAR-RED 1（HFR1）被认为是通过与其他碱性螺旋-环-螺旋（bHLH）转录因子形成异二聚体来抑制它们，从而成为 SAS 的负调节剂，但它在全基因组转录调控中的功能尚未完全阐明。在这里，我们对拟南芥 hfr1-5 突变体和 HFR1 过表达系[HFR1（ΔN）-OE]进行了 RNA-seq 分析，以全面鉴定在不同遮荫处理时间点受 HFR1 调控的基因。我们发现 HFR1 通过调节遮荫下相关基因的表达，介导了遮荫诱导生长和遮荫抑制防御之间的权衡。促进生长的相关基因，如生长素的生物合成、运输、信号转导和响应，在短时间和长时间遮荫下均被遮荫诱导，但被 HFR1 抑制。同样，大多数乙烯相关基因被遮荫诱导，而被 HFR1 抑制。然而，遮荫抑制防御相关基因，而 HFR1 诱导其表达，特别是在长时间遮荫处理下。我们证明了 HFR1 在遮荫下赋予了对细菌感染的更高抗性。
