热胁迫下莴苣种子萌发的转录组和代谢组解析

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Transcriptomic and Metabolomic Analysis ofLettuce （Lactuca sativa L.） Seed Germination under Heat Stress

WEI Jinpeng1，²，ZHANGQi1，YANGLe1，²，ZHOU Yuliang²，CHENBingxian1 （Agro-BiologicalGeneResearchCenter，GuangdongAcademyofAgricultural Sciences/GuangdongProvincialKey Laboratory for CropGermplasmResources Preservation and Utilization，Guangzhou510640; 2CollegeofAgriculture，SouthChina Agricultural University，Guangzhou 510642）

Abstract：In order to elucidate the molecular mechanismof lettuce seed germination under heat stress，the transcriptome，metabolome and multi-omics combined analysis were performed on the seeds of two letuce varieties，heat-tolerant cultivar Italian Letuceand heat-sensitive cultivar Four-Season Fodder Lettuce. Untargeted metabolomicsidentified 391 differentially expressd metabolites（DEMs），revealing specific activationof the tyrosine metabolismand flavonoid biosynthesis pathways.Metabolites including muconic acid， L-tyrosine，L-tyramine，and p-hydroxycinnamic acid were significantly enriched.Transcriptomeanalysis detected 3127 diffrentially expressed genes （DEGs），indicating two distinct genetic regulatory mechanisms associated with early thermotolerance in letuce germination：（1）Unique upregulation of heat shock protein （HSP）-related genes in Italian Lettuce；（2） Activation of β -glucanase-coding genes by AP2/ERF transcription factors，facilitating repair of heat-damaged cell wall.Keycandidate genes were initially screened using Gene

SetEnrichment Analysis（GSEA）combined with protein-protein interaction（PPI）network analysis.qRT-PCR validation corroborated theRNA-seq findings.Integrated multi-omicsanalysis demonstrated significant downregulation of ethylene biosynthesis genes（ACO，1-Aminocyclopropane-1-Carboxylate Oxidase）inFourSeason Fodder Lettuce.Concurrent suppression occurred in core flavonoid pathway genes， β -glucosidaseencoding genes，and biosynthesis ofaromatic amino acids（tyrosine）.These results indicate that heat stress inhibits seed germination through a dual mechanism involving metabolic flux blockage and inactivation of the antioxidant defense system.This study delineates the gene-metaboliteregulatory network underlying the heatstress response during lettuce seed germination，providing a theoretical foundation for the molecular interactions governing germination inhibition.

Key words：lettuce seed;heat stress;flavonoids;transcriptome-metabolomecombinationanalysis;qRT-PCR

高温是限制冷季蔬菜莴苣（LactucasativaL.）种子萌发的关键因素之一。（剩余25069字）