State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, 866 Yu Hangtang Road, Hangzhou, Zhejiang 310058, China.
Hangzhou Botanical Garden, Taoyuanling Road, Hangzhou, Zhejiang 310013, China.
Mol Plant. 2023 May 1;16(5):809-828. doi: 10.1016/j.molp.2023.03.005. Epub 2023 Mar 9.
The secondary vascular tissue emanating from meristems is central to understanding how vascular plants such as forest trees evolve, grow, and regulate secondary radial growth. However, the overall molecular characterization of meristem origins and developmental trajectories from primary to secondary vascular tissues in woody tree stems is technically challenging. In this study, we combined high-resolution anatomic analysis with a spatial transcriptome (ST) technique to define features of meristematic cells in a developmental gradient from primary to secondary vascular tissues in poplar stems. The tissue-specific gene expression of meristems and derived vascular tissue types were accordingly mapped to specific anatomical domains. Pseudotime analyses were used to track the origins and changes of meristems throughout the development from primary to secondary vascular tissues. Surprisingly, two types of meristematic-like cell pools within secondary vascular tissues were inferred based on high-resolution microscopy combined with ST, and the results were confirmed by in situ hybridization of, transgenic trees, and single-cell sequencing. The rectangle shape procambium-like (PCL) cells develop from procambium meristematic cells and are located within the phloem domain to produce phloem cells, whereas fusiform shape cambium zone (CZ) meristematic cells develop from fusiform metacambium meristematic cells and are located inside the CZ to produce xylem cells. The gene expression atlas and transcriptional networks spanning the primary transition to secondary vascular tissues generated in this work provide new resources for studying the regulation of meristem activities and the evolution of vascular plants. A web server (https://pgx.zju.edu.cn/stRNAPal/) was also established to facilitate the use of ST RNA-seq data.
次生维管组织起源于分生组织，这对于理解森林树木等维管植物如何进化、生长和调节次生径向生长至关重要。然而，从初生到次生木质部的茎干木质部分生组织起源和发育轨迹的全面分子特征在技术上具有挑战性。在这项研究中，我们将高分辨率解剖分析与空间转录组（ST）技术相结合，以定义杨树茎中从初生到次生维管组织的分生组织细胞在发育梯度中的特征。相应地，将分生组织和衍生的维管组织类型的组织特异性基因表达图谱绘制到特定的解剖结构域。拟时分析用于追踪从初生到次生维管组织的发育过程中分生组织的起源和变化。令人惊讶的是，基于高分辨率显微镜结合 ST，推断出次生维管组织内存在两种类型的分生组织样细胞池，并且通过原位杂交、转基因树木和单细胞测序对结果进行了验证。矩形形状原形成层样（PCL）细胞由原形成层分生组织细胞发育而来，位于韧皮部区域内以产生韧皮部细胞，而梭形形状形成层区（CZ）分生组织细胞由梭形后生分生组织细胞发育而来，位于 CZ 内以产生木质部细胞。本工作中生成的跨越初生到次生维管组织转变的基因表达图谱和转录网络为研究分生组织活性的调控和维管植物的进化提供了新的资源。还建立了一个网络服务器（https://pgx.zju.edu.cn/stRNAPal/），以方便使用 ST RNA-seq 数据。
