Key Laboratory of Horticultural Crop Biology and Germplasm Innovation (Ministry of Agriculture), Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China; Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, China Agricultural University, Beijing, 100193, China.
Key Laboratory of Horticultural Crop Biology and Germplasm Innovation (Ministry of Agriculture), Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
Plant Sci. 2021 Mar;304:110803. doi: 10.1016/j.plantsci.2020.110803. Epub 2020 Dec 24.
Grafting is widely used worldwide because of its obvious advantages, especially in solanaceous vegetable crops. However, the molecular mechanisms underlying graft formation are unknown. In this study, internode tissues from above and below the graft junction were harvested, and we performed weighted gene co-expression network analysis (WGCNA) to describe the temporal and spatial transcriptional dynamics that occur during graft formation in tomato. The wounding stress response involved in JA, ETH, and oxylipins mainly occurred at 1 h after grafting (HAG). From 3 to 12 HAG, the biological processes of snRNA and snoRNA modification and the gibberellin-mediated signaling pathway functioned both above and below the graft junction. However, auxin transport and signaling, DNA replication, and xylem and phloem pattern formation were restricted to the scion, whereas the cytokinin-activated signaling pathway and the cellular response to sucrose starvation was restricted to the rootstock. At 24-72 HAG, cell division occurred above the graft junction, and photosynthesis-related pathways were activated below the graft junction. The levels of auxin and cytokinin reached their maxima above and below the graft junction at 12 HAG, respectively. Exogenous application of certain concentrations of IAA and 6-BA will promote xylem and phloem transport capacity. The current work has analyzed the stage-specific events and hub genes during the developmental progression of tomato grafting. We found that auxin and cytokinin levels respond to grafting, above and below the graft junction, respectively, to promote the formation of xylem and phloem patterning. In addition, the accumulation of auxin above the graft junction induced cells to prepare for mitosis and promoted the formation of callus. In short, our work provides an important reference for theoretical research and production application of tomato grafting in the future.
嫁接在全球范围内得到广泛应用，因为它具有明显的优势，特别是在茄科蔬菜作物中。然而，嫁接形成的分子机制尚不清楚。在这项研究中，我们采集了嫁接结合部上下的节间组织，并进行了加权基因共表达网络分析（WGCNA），以描述番茄嫁接过程中发生的时空转录动态。JA、ETH 和氧化脂类参与的创伤应激反应主要发生在嫁接后 1 小时（HAG）。从 3 到 12 HAG，snRNA 和 snoRNA 修饰的生物学过程和赤霉素介导的信号通路在嫁接结合部的上下部都起作用。然而，生长素运输和信号、DNA 复制以及木质部和韧皮部模式形成仅限于接穗，而细胞分裂素激活的信号通路和细胞对蔗糖饥饿的反应仅限于砧木。在 24-72 HAG，细胞分裂发生在嫁接结合部上方，光合作用相关途径在嫁接结合部下方被激活。生长素和细胞分裂素的水平分别在嫁接结合部的上下部于 12 HAG 达到最大值。IAA 和 6-BA 的某些浓度的外源应用将促进木质部和韧皮部的运输能力。目前的工作分析了番茄嫁接发育过程中特定阶段的事件和枢纽基因。我们发现，生长素和细胞分裂素水平分别在嫁接结合部的上下部响应嫁接，以促进木质部和韧皮部模式的形成。此外，嫁接结合部上方生长素的积累诱导细胞准备有丝分裂，并促进愈伤组织的形成。总之，我们的工作为未来番茄嫁接的理论研究和生产应用提供了重要参考。
