Center for Genomics and Biotechnology, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
J Plant Physiol. 2021 May;260:153405. doi: 10.1016/j.jplph.2021.153405. Epub 2021 Mar 8.
In vitro organogenesis is a multistep process which is largely controlled by the balance between auxin and cytokinin. Previous studies revealed a complex network regulating in vitro organogenesis in Arabidopsis thaliana; however, our knowledge of the molecular mechanisms underlying de novo shoot formation in papaya (Carica papaya) remains limited. Here, we optimized multiple factors to achieve an efficient and reproducible protocol for the induction of papaya callus formation and shoot regeneration. Subsequently, we analyzed the dynamic transcriptome profiles of samples undergoing this process, identified 5381, 642, 4047, and 2386 differentially expressed genes (DEGs), including 447, 66, 350, and 263 encoding transcription factors (TFs), in four stage comparisons. The DEGs were mainly involved in phytohormone modulation and transduction processes, particularly for auxin and cytokinin. Of these, 21 and 7 candidate genes involved in the auxin and cytokinin pathways, respectively, had distinct expression patterns throughout in vitro organogenesis. Furthermore, we found two genes encoding key TFs, CpLBD19 and CpESR1, were sharply induced on callus induction medium and shoot induction medium, indicating these two TFs may serve as proxies for callus induction and shoot formation in papaya. We therefore report a regulatory network of auxin and cytokinin signaling in papaya according to the one previously modeled for Arabidopsis. Our comprehensive analyses provide insight into the early molecular regulation of callus initiation and shoot formation in papaya, and are useful for the further identification of the regulators governing in vitro organogenesis.
体外器官发生是一个多步骤的过程，主要由生长素和细胞分裂素之间的平衡控制。以前的研究揭示了一个复杂的网络来调节拟南芥的体外器官发生；然而，我们对木瓜（Carica papaya）中从头形成新梢的分子机制的了解仍然有限。在这里，我们优化了多个因素，以实现一种高效且可重复的方法来诱导木瓜愈伤组织形成和芽再生。随后，我们分析了经历这一过程的样品的动态转录组谱，在四个阶段的比较中鉴定了 5381、642、4047 和 2386 个差异表达基因（DEGs），包括 447、66、350 和 263 个编码转录因子（TFs）。DEGs 主要参与植物激素的调节和转导过程，特别是生长素和细胞分裂素。其中，21 和 7 个候选基因分别参与生长素和细胞分裂素途径，在体外器官发生过程中表现出不同的表达模式。此外，我们发现两个编码关键 TF 的基因，CpLBD19 和 CpESR1，在愈伤组织诱导培养基和芽诱导培养基中被强烈诱导，表明这两个 TF 可能作为木瓜愈伤组织诱导和芽形成的代表。因此，我们根据拟南芥模型报告了一个在木瓜中生长素和细胞分裂素信号转导的调控网络。我们的综合分析为木瓜中愈伤组织起始和芽形成的早期分子调控提供了深入的了解，并有助于进一步鉴定控制体外器官发生的调节剂。
