WANG Xue-Ting1, LIANG Man-Man1, LI Han2, QI Guo-Hui2, SHEN Yan-Hong1,*
1 College of Horticultural Science ＆ Technology/Hebei Key Laboratory of Horticultural Germplasm Excavation and Innovative Utilization, Hebei Normal University of Science ＆ Technology, Qinhuangdao 066000, China; 2 College of Forestry, Hebei Agricultural University, Baoding 071000, China
Abstract：Walnut (Juglans regia) is highly valued by consumers for its distinctive aroma, yet the molecular mechanisms underlying its aroma formation remain unclear. In this study, fresh 'Qingxiang' walnut kernels were analyzed using headspace solid-phase microextraction (HS-SPME)-gas chromatography-mass spectrometry (GC-MS) and transcriptome sequencing (RNA-seq) to systematically investigate the dynamic changes in aroma-related genes and volatile compounds during kernel development from 85 to 141 d after flowering. GC-MS analysis identified 70 volatile organic compounds (VOCs), with aldehydes (e.g., nonanal), alcohols (e.g., 1-octen-3-ol), and ketones (e.g., 3-octanone) as key aroma contributors. Based on odor activity value (OAV>1), 11 core aroma-active compounds were screened, including (E)-2-butenal and hexanal. Transcriptome analysis revealed that differentially expressed genes (DEGs) during fruit maturation were significantly enriched in starch and sucrose metabolism (94), pyruvate metabolism (66), fatty acid biosynthesis (39), terpenoid backbone biosynthesis (35), α-linolenic acid metabolism (36), and fatty acid degradation (29). Further integration of omics data and aroma dynamics enabled the construction of a regulatory network for aldehyde and ketone biosynthesis, It was found that hydroperoxide lyase (HPL) coding gene JrHPL, alcohol dehydrogenase (ADH) coding genes JrADH_7 and JrADH_8, and aldehyde dehydrogenase (ALDH) coding gene JrALDH_7 play key roles in aroma metabolism. This study reveals the multi-omics regulatory mechanism of walnut aroma formation, offering a theoretical reference for molecular breeding strategies to enhance nut flavor.
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