基于转录组与代谢组学联合分析干化处理对沙地云杉成熟体细胞胚胎的影响

Integrated transcriptomics and metabolomics analyses of the effects of desiccation treatment on mature somatic embryos of Picea mongolica

摘要:

沙地云杉(Picea mongolica)为我国特有珍稀树种，体细胞胚胎发生技术的应用对其良种繁育具有重要意义。然而，体细胞胚胎脱水耐受性获得机制尚不明确，制约了人工种子的开发与应用。本研究旨在通过干化处理模拟脱水胁迫，解析沙地云杉成熟体胚的代谢响应网络，揭示其适应脱水胁迫的核心调控通路。本研究以沙地云杉成熟体细胞胚胎为材料，通过干化处理模拟脱水胁迫，综合运用转录组学与广泛靶向代谢组学技术进行分析。结果显示，干化处理引发了大规模的转录与代谢响应，共鉴定到15 723个差异表达基因与91个差异代谢物。基因功能富集分析表明，差异基因显著富集于细胞膜/壁组织、苯丙烷生物合成及植物激素信号等通路。代谢物则显著富集于丙氨酸、天冬氨酸和谷氨酸代谢、植物激素生物合成和植物次生代谢物生物合成等途径。丙氨酸、天冬氨酸和谷氨酸代谢是唯一在转录与代谢层面均显著富集的核心通路；三羧酸循环(tricarboxylic acid cycle, TCA)上游被激活，异柠檬酸脱氢酶编码基因的表达量显著上调，伴随异柠檬酸与α-酮戊二酸的极显著积累。谷氨酰胺合成酶基因与天冬酰胺合成酶基因表达显著上调，驱动了l-谷氨酰胺与l-天冬酰胺的优先积累，而4-氨基丁酸支路产物含量显著下降。本研究系统阐明了沙地云杉体细胞胚胎通过协同调控丙氨酸、天冬氨酸和谷氨酸代谢通路、实施“开源节流”策略以适应干化胁迫，为通过代谢工程靶向改良林木体细胞胚胎质量提供了重要的理论依据与关键分子靶标。

Abstract:

Picea mongolica, a rare and endemic conifer in China, holds great value for afforestation in arid regions. Somatic embryogenesis represents a key biotechnology for its clonal propagation. However, the mechanisms governing the acquisition of desiccation tolerance in somatic embryos remain poorly understood, hindering the development and application of synthetic seeds. In this study, desiccation treatment was performed on the mature somatic embryos of P. mongolica to simulate dehydration stress. Integrated transcriptomics and widely targeted metabolomics analyses were performed to unravel the underlying adaption mechanisms. The treatment triggered extensive molecular reprogramming, leading to the identification of 15 723 differentially expressed genes (DEGs) and 91 differentially accumulated metabolites (DAMs). Functional enrichment analysis revealed that DEGs were significantly associated with cell wall/membrane remodeling, phenylpropanoid biosynthesis, and plant hormone signaling. DAMs were significantly enriched in pathways such as alanine, aspartate and glutamate metabolism, biosynthesis of plant hormones, and biosynthesis of plant secondary metabolites. Strikingly, alanine, aspartate and glutamate metabolism emerged as the central hub, being the only pathway significantly enriched at both omics levels. Within this nexus, desiccation activated the upstream tricarboxylic acid cycle, evidenced by the up-regulation of the isocitrate dehydrogenase 1 gene and substantial accumulation of isocitrate and α-ketoglutarate. Concurrently, the genes encoding glutamine synthetase and asparagine synthetase were strongly induced, channeling nitrogen flux toward the accumulation of l-glutamine and l-asparagine, while metabolites in the 4-aminobutyrate shunt significantly decreased. Collectively, our findings delineate a coordinated carbon supply and nitrogen channeling metabolic reprogramming strategy in P. mongolica somatic embryos to cope with desiccation. This study provides not only a systematic understanding of dehydration tolerance in woody somatic embryos but also a foundational framework and specific molecular targets for quality improvement via metabolic engineering.