马尾松不同分枝类型的顶芽内源激素、转录组与代谢组分析

Analysis of endogenous hormones, metabolome and transcriptome in apical buds of Pinus massoniana with different branching types

关键词:  马尾松, 分枝, 转录组测序, 差异表达基因, 内源激素

Key words:  Pinus massoniana, branching, transcriptome sequencing, differentially expressed genes, endogenous hormones

摘要:

对通直度、节间长、分枝等性状的改良是马尾松育种的重要目标,其中分枝直接影响其干形和木材产量。为探究马尾松不同分枝类型形成的机制,该研究以狐尾型、多干型与正常分枝型马尾松为对象,对顶芽的激素含量、代谢组和转录组进行分析。结果表明:(1)3种分枝类型马尾松顶芽的生长素(IAA)、细胞分裂素(CTK)、脱落酸(ABA)、赤霉素(GA)的含量存在显著性差异,表现为多干型>正常分枝型>狐尾型; 狐尾型的IAA/ABA和IAA/CTK比值最大,多干型最小。激素物质主要富集在植物激素信号转导途径、玉米素生物合成等通路。(2)差异表达基因的KEGG分析显著富集到玉米素生物合成、氨基酸代谢、戊糖和葡萄糖醛酸相互转化等通路,进一步筛选获得与植物激素信号转导途径相关的35个差异表达基因。(3)联合分析发现,细胞分裂素和生长素及其有关物质与基因参与调控马尾松的分枝过程,其中色胺、吲哚、反式玉米素等在狐尾型马尾松中上调表达,二氢玉米素核苷等在多干型马尾松中呈上调趋势。该研究初步揭示了马尾松产生分枝现象的差异激素和调控机制,为利用激素调控马尾松的分枝提供了参考。

Abstract:

The improvement of traits including stem straightness, internode length, and branching is an important breeding objective for Pinus massoniana, as branching directly affects stem form and timber yield. To explore the mechanisms underlying the formation of different branching types in P. massoniana, this study used fox-tail type, multi-stem type, and normal branching type P. massoniana as materials, and analyzed the hormone contents, metabolome, and transcriptome of apical buds. The results were as follows:(1)The contents of four key endogenous hormones — auxin(IAA), cytokinin(CTK), abscisic acid(ABA), and gibberellin(GA)— in the apical buds of the three branching types differed significantly, following the order multi-stem type > normal branching type > fox-tail type. The ratios of IAA/ABA and IAA/CTK were highest in the fox-tail type and lowest in the multi-stem type. Hormone-related metabolites were predominantly enriched in pathways such as plant hormone signal transduction and zeatin biosynthesis, which are closely associated with the regulation of plant growth and branching development.(2)Kyoto encyclopedia of genes and genomes(KEGG)analysis of differentially expressed genes(DEGs)revealed significant enrichment in pathways including zeatin biosynthesis, amino acid metabolism, and pentose and glucuronate interconversion. Further functional annotation and rigorous screening identified 35 DEGs specifically associated with the plant hormone signal transduction pathway, thereby highlighting the central role of transcriptional regulation in the formation of branching traits in P. massoniana.(3)Integrated analysis indicated that cytokinins, auxins, and their associated metabolites and regulatory genes participated in the branching process of P. massoniana. Specifically, compounds such as tryptamine, indole, and trans-zeatin showed an upregulated trend in the fox-tail type, while dihydrozeatin riboside showed an upregulated trend in the multi-stem type. This study preliminarily elucidates the differential hormones and regulatory mechanisms underlying branching variation in P. massoniana, providing a reference for hormone-mediated branching regulation in P. massoniana.