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 branch 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,branch,transcriptome analysis,metabolome,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、多干型与正常类型马尾松为对象，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、细胞分裂素、脱落酸、赤霉素的含量存在显著差异，表现为多干型>正常分枝>狐尾型；狐尾型的IAA/ABA和IAA/CTK的比值最大，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、戊糖和葡萄糖醛酸的相互转化等通路，进一步筛选获得植物激素信号转导途径相关的差异表达基因35个。（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，双氢玉米素核苷等在多干型马尾松中呈上调趋势。该研究初步揭示马尾松产生分枝现象的差异激素和调控机制，为激素调控马尾松的分枝提供参考。

Abstract:

The improvement of traits including stem straightness, internode length, and branching is an important breeding objective for Pinus massoniana breeding, as branching directly affects stem form and timber yield. To systematically decipher the molecular and physiological mechanisms underlying the formation of distinct branching phenotypes in Pinus massoniana, this study integrated targeted hormone quantification, metabolomic profiling, and high-throughput transcriptomic sequencing to analyze apical buds from three representative branching types: fox-tail type, multi-stem type, and normal type. The results showed that: (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, with accumulation levels following the order multi-stem type > normal 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 encyclopediaof genesand genomes (KEGG) enrichment analysis of differentially expressed genes (DEGs) revealed that significant enrichment in pathways including zeatin biosynthesis, amino acid metabolism, and pentose and glucuronate interconversions. Further functional annotation and strict 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 Pinus massoniana. (3) Integrated analysis indicated that cytokinins, auxins, and their associated metabolites and corresponding regulatory genes play a regulatory role in the branching process of Pinus massoniana. Specifically, compounds such as tryptamine, indole, and trans-zeatin showed an upward trend in the fox-tail type, while dihydrozeatin ribonucleoside showed an increasing trend in the multi-stem type. This study preliminarily elucidates the differential hormonal and regulatory mechanisms underlying branching variation in Pinus massoniana, providing a reference for endogenous hormone mediated branching regulation in this species.