Transcriptome analysis of isoxaben-induced loss of cell wall integrity in Arabidopsis seedling liquid culture

Plant cells are surrounded by walls, which must often meet opposing functional requirements during plant growth and defense. The cells meet them by modifying wall structure and composition in a tightly controlled and adaptive manner. The modifications seem to be mediated by a dedicated cell wall integrity (CWI) maintenance mechanism. Currently the mode of action of the mechanism is not understood and it is unclear how its activity is coordinated with established plant defense signaling. We investigated both the responses to cell wall damage (CWD) compromising CWI and the underlying mechanism in Arabidopsis thaliana. A cellulose biosynthesis inhibitor isoxaben was used as a tool to induce the loss of cell wall integrity. Isoxaben was chosen because it only affects a certain cell type / differentiation stage, and weakens the cell walls indirectly by inhibiting a biosynthetic process, making CWD occurrence dependent on high turgor levels (allowing simultaneous manipulation of the responses by addition of osmotica like sorbitol, mannitol, etc.). Isoxaben treatment causes structural damage, induction of lesion formation, cell death, deposition of lignin and callose as well as production of jasmonic acid and salicylic acid. Isoxaben-resistant mutant ixr1-1 is included to ensure the specificity of the treatment. Both genotypes (Col-0 and ixr1-1) were treated with either isoxaben or DMSO (mock). Three replicates of each sample were analyzed.

植物细胞被细胞壁包被，在植物生长与防御过程中，细胞壁往往需要兼顾相互对立的功能需求。植物细胞通过受严密调控且具有适应性的方式修饰细胞壁的结构与组成，以此协调这些功能需求。这类修饰似乎由一套专门的细胞壁完整性（cell wall integrity, CWI）维持机制所介导。目前，该机制的作用模式尚未阐明，其活性如何与已确立的植物防御信号通路相协调也尚不明确。本研究以拟南芥（Arabidopsis thaliana）为材料，探究了破坏细胞壁完整性的细胞壁损伤（cell wall damage, CWD）响应及其潜在调控机制。研究选用纤维素生物合成抑制剂异恶草胺（isoxaben）作为诱导细胞壁完整性丧失的工具试剂。选择异恶草胺的原因在于，其仅作用于特定细胞类型/分化阶段，且通过抑制生物合成过程间接削弱细胞壁，使得细胞壁损伤的发生依赖于高膨压水平——这一特性允许通过添加山梨醇、甘露醇等渗透压调节剂同步调控相关响应过程。异恶草胺处理会引发细胞壁结构损伤、病斑形成、细胞死亡、木质素与胼胝质沉积，同时诱导茉莉酸与水杨酸的生成。本研究设置异恶草胺抗性突变体ixr1-1作为对照，以确保处理的特异性。分别对两种基因型材料（Col-0与ixr1-1）施加异恶草胺处理或二甲基亚砜（DMSO，空白对照）处理。每个样本设置三次生物学重复并进行分析。