Michael Smith Laboratories, University of British Columbia, 301-2185 East Mall, Vancouver, BC, V6T 1Z4, Canada.
Forest Improvement and Research Management Branch, British Columbia Ministry of Forests, Lands, and Natural Resource Operations and Rural Development, 7380 Puckle Road, Saanichton, BC, V8M 1W4, Canada.
New Phytol. 2023 Sep;239(6):2138-2152. doi: 10.1111/nph.19103. Epub 2023 Jul 4.
Stone cells are a specialized, highly lignified cell type found in both angiosperms and gymnosperms. In conifers, abundance of stone cells in the cortex provides a robust constitutive physical defense against stem feeding insects. Stone cells are a major insect-resistance trait in Sitka spruce (Picea sitchensis), occurring in dense clusters in apical shoots of trees resistant (R) to spruce weevil (Pissodes strobi) but being rare in susceptible (S) trees. To learn more about molecular mechanisms of stone cell formation in conifers, we used laser microdissection and RNA sequencing to develop cell-type-specific transcriptomes of developing stone cells from R and S trees. Using light, immunohistochemical, and fluorescence microscopy, we also visualized the deposition of cellulose, xylan, and lignin associated with stone cell development. A total of 1293 genes were differentially expressed at higher levels in developing stone cells relative to cortical parenchyma. Genes with potential roles in stone cell secondary cell wall formation (SCW) were identified and their expression evaluated over a time course of stone cell formation in R and S trees. The expression of several transcriptional regulators was associated with stone cell formation, including a NAC family transcription factor and several genes annotated as MYB transcription factors with known roles in SCW formation.
石细胞是一种特化的、高度木质化的细胞类型，存在于被子植物和裸子植物中。在针叶树中，皮层中石细胞的丰富程度为茎部取食昆虫提供了强大的固有物理防御。石细胞是西特卡云杉（Picea sitchensis）的主要抗虫性状，在对云杉象鼻虫（Pissodes strobi）具有抗性（R）的树木的顶梢密集地聚集，但在易感（S）树木中则很少见。为了更多地了解针叶树中石细胞形成的分子机制，我们使用激光显微切割和 RNA 测序，从 R 和 S 树上发育中的石细胞中开发出细胞类型特异性转录组。我们还使用光、免疫组织化学和荧光显微镜，可视化与石细胞发育相关的纤维素、木聚糖和木质素的沉积。与皮层薄壁组织相比，在发育中的石细胞中，有 1293 个基因的表达水平更高。鉴定了具有潜在作用的基因在石细胞次生细胞壁形成（SCW）中的作用，并在 R 和 S 树上的石细胞形成过程中评估了它们的表达。几个转录调节因子的表达与石细胞的形成有关，包括一个 NAC 家族转录因子和几个被注释为 MYB 转录因子的基因，它们在 SCW 形成中具有已知的作用。
