转录组分析揭示了柑橘顶端优势调控腋芽生长的关键网络。

National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops / College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, PR China.

Gene. 2024 Oct 30;926:148623. doi: 10.1016/j.gene.2024.148623. Epub 2024 May 29.

Topping, an important tree shaping and pruning technique, can promote the outgrowth of citrus axillary buds. However, the underlying molecular mechanism is still unclear. In this study, spring shoots of Citrus reticulata 'Huagan No.2' were topped and transcriptome was compared between axillary buds of topped and untopped shoots at 6 and 11 days after topping (DAT). 1944 and 2394 differentially expressed genes (DEGs) were found at 6 and 11 DAT, respectively. KEGG analysis revealed that many DEGs were related to starch and sucrose metabolism, signal transduction of auxin, cytokinin and abscisic acid. Specially, transcript levels of auxin synthesis, transport, and signaling-related genes (SAURs and ARF5), cytokinin signal transduction related genes (CRE1, AHP and Type-A ARRs), ABA signal responsive genes (PYL and ABF) were up-regulated by topping; while transcript levels of auxin receptor TIR1, auxin responsive genes AUX/IAAs, ABA signal transduction related gene PP2Cs and synthesis related genes NCED3 were down-regulated. On the other hand, the contents of sucrose and fructose in axillary buds of topped shoots were significantly higher than those in untopped shoots; transcript levels of 16 genes related to sucrose synthase, hexokinase, sucrose phosphate synthase, endoglucanase and glucosidase, were up-regulated in axillary buds after topping. In addition, transcript levels of genes related to trehalose 6-phosphate metabolism and glycolysis/tricarboxylic acid (TCA) cycle, as well to some transcription factors including Pkinase, Pkinase_Tyr, Kinesin, AP2/ERF, P450, MYB, NAC and Cyclin_c, significantly responded to topping. Taken together, the present results suggested that topping promoted citrus axillary bud outgrowth through comprehensively regulating plant hormone and carbohydrate metabolism, as well as signal transduction. These results deepened our understanding of citrus axillary bud outgrowth by topping and laid a foundation for further research on the molecular mechanisms of citrus axillary bud outgrowth.

摘心是一种重要的整形和修剪技术，可以促进柑橘腋芽的生长。然而，其潜在的分子机制尚不清楚。在这项研究中，以‘华柑 2 号’春梢为试材，在摘心后 6 和 11 天（DAT）比较摘心和未摘心春梢腋芽的转录组。分别在 6 和 11 DAT 发现了 1944 和 2394 个差异表达基因（DEGs）。KEGG 分析表明，许多 DEGs 与淀粉和蔗糖代谢、生长素、细胞分裂素和脱落酸的信号转导有关。特别地，生长素合成、运输和信号转导相关基因（SAURs 和 ARF5）、细胞分裂素信号转导相关基因（CRE1、AHP 和 Type-A ARRs）、ABA 信号响应基因（PYL 和 ABF）的转录水平在摘心后上调；而生长素受体 TIR1、生长素响应基因 AUX/IAAs、ABA 信号转导相关基因 PP2Cs 和合成相关基因 NCED3 的转录水平下调。另一方面，摘心春梢腋芽中的蔗糖和果糖含量明显高于未摘心春梢；蔗糖合酶、己糖激酶、蔗糖磷酸合酶、内切葡聚糖酶和葡糖苷酶相关的 16 个基因在摘心后在腋芽中上调表达。此外，海藻糖 6-磷酸代谢和糖酵解/三羧酸（TCA）循环以及一些转录因子（包括 Pkinase、Pkinase_Tyr、Kinesin、AP2/ERF、P450、MYB、NAC 和 Cyclin_c）的相关基因的转录水平对摘心有明显响应。总之，本研究结果表明，通过综合调节植物激素和碳水化合物代谢以及信号转导，摘心促进了柑橘腋芽的生长。这些结果加深了我们对柑橘腋芽生长的理解，为进一步研究柑橘腋芽生长的分子机制奠定了基础。