Transcriptomic profiling of Arabidopsis hypocotyls of brl3 mutants and tissue-specific overexpressors under elevated temperatures. Transcriptomic profiling of Arabidopsis hypocotyls of brl3 mutants and tissue-specific overexpressors under elevated temperatures

Climate change is having a drastic impact on global agriculture. Indeed stress factors such as elevated temperature, drought and rising atmospheric CO2 reduce arable land surface, crop cultivation and yield and overall sustainable food production on earth. However, plants possess immense innate adaptive plasticity and a more in-depth understanding of the underlying molecular mechanisms is crucial to strategize for sustaining populations under worsening climate change. Brassinosteroids (BRs) are constitutive plant growth regulators that also control plant adaptation to abiotic stress. Downstream components of the BR biosynthetic pathway, BES1/BZR1 play central role in thermomorphogenesis, but involvement of the BR receptors is not well understood. Here, we show that the BRL3 receptor is essential for plant adaptation to warmer environment. The brl3 mutants lack thermal responsiveness and the BRL3 overexpression causes hyper-thermomorphogenesis response. BRL3 activates canonical BRI1 pathway upon elevated temperature. Further, phloem-specific expression of BRL3 completely rescues the growth adaptation defects of the brl3 mutant. This ability of BRL3 represents a previously unknown thermoresponsive mechanism specifically from phloem and uncouples the roles of BR receptors in generic growth vs adaptation to changing climate conditions. Overall design: A two factor experimental design (Genotype and temperature) with several levels in genotype factor: The hypocotyl of 6-day-old Arabidopsis seedlings of Col-0 (WT), brl3 mutant (SALK_006024C), phloem-complemented line pSUC2:BRL3-GFP; brl3-2 and BRL3ox (35S:BRL3-GFP, Fàbregas et al., 2018) grown at 22ºC (growth optimum) and 28ºC (elevated temperature) were sampled and RNA sequenced. Two biological replicates per genotype and condition. A total of 16 samples.

气候变化正对全球农业造成剧烈冲击。事实上，高温、干旱以及大气CO₂浓度升高等胁迫因子，会缩减全球可耕地面积、抑制作物种植与产量，并破坏整体可持续粮食生产。然而，植物拥有极强的先天适应性可塑性；深入解析其背后的分子机制，对于制定策略以在日益恶化的气候变化背景下维持人类粮食供给至关重要。油菜素类固醇（Brassinosteroids, BRs）是组成型植物生长调节物质，同时亦可调控植物对非生物胁迫的适应性。BR生物合成通路的下游组分BES1/BZR1在热形态建成中发挥核心作用，但BR受体的参与机制尚未得到充分阐明。本研究证实，BRL3受体对于植物适应高温环境不可或缺。brl3突变体丧失热响应能力，而BRL3过表达则会引发超敏热形态建成反应。在温度升高时，BRL3会激活经典的BRI1信号通路。进一步研究发现，仅在韧皮部特异性表达BRL3，即可完全恢复brl3突变体的生长适应缺陷。BRL3的这一功能揭示了一种此前未被发现的、源自韧皮部的热响应机制，同时厘清了BR受体在一般性生长与气候变化适应性中的不同功能。整体实验设计：采用基因型与温度双因素实验设计，基因型因素包含多个组别：将6日龄拟南芥幼苗的下胚轴样本分为Col-0（野生型WT）、brl3突变体（SALK_006024C）、韧皮部互补株系pSUC2:BRL3-GFP; brl3-2以及BRL3过表达株系BRL3ox（35S:BRL3-GFP, Fàbregas et al., 2018），分别在22℃（适宜生长温度）与28℃（高温胁迫）条件下培养后取样，进行RNA测序。每个基因型与条件设置2个生物学重复，总计16个样本。