Genome-wide identification and effect on volatile aroma compounds of lipoxygenase in fruit fatty acid metabolism pathway in Capsicum chinense
Kun Wu, Mengxian Yang, Lianzhu Chen, Lijun Ou, Zhoubin Liu, Qin Deng, Renquan Huang, Muhammad Ahsan Altaf, Zhiwei Wang, Lu Xu, Huizhen Fu, Shanhan Cheng
Abstract
• Sixteen LOX genes were identified in the Capsicum chinense genome, revealing genomic features of LOXs in chili peppers and providing insights through bioinformatic analyses. • qRT-PCR analysis showed that LOX gene expression patterns varied among chili peppers with different pungency levels. • Metabolomic analysis further revealed that the expression of certain CcLOX genes was positively correlated with the accumulation of specific aldehydes. Additionally, expression levels of ADH and AAT , two key genes downstream in the fatty acid metabolism pathway, were also positively correlated with the accumulation of related metabolites. • This research provides a foundation for future research on how fatty acid metabolism-related genes regulate the formation of chili fruit aroma. Volatile aroma compounds (VACs), including aldehydes, alcohols, and esters derived from the fatty acid metabolism pathway (FAP), enable plants to produce distinct aroma profiles. Lipoxygenase (LOX) is a key enzyme in this pathway, significantly affecting the aroma components and content of fruits and vegetables. However, the role of LOXs in the biosynthesis and regulation of VACs in chili remains unclear. In this study, we identified the genomic information of LOXs in peppers and analyzed their expression characteristics across different chili varieties and fruit development stages. We also investigated the relationship between changes in fatty acid pathway enzymes and VAC content. The results showed that 16 LOX genes are present in the Capsicum chinense genome, with nine located on known chromosomes and four in tandem repeats on chromosome 1. qRT-PCR analysis revealed that 9S-LOX expression was higher in peppers with greater spiciness, while 13S-LOX expression was higher in peppers with lower spiciness. Metabolomic analysis revealed that ester accumulation, including 4-methylpentyl 3-methylbutanoate, varied across peppers with different pungency levels, leading to distinct aroma profiles. Combining expression levels with metabolomics data, we found that the expression levels of CcLOX1, CcLOX4, CcLOX5, and CcLOX12 were positively correlated with the accumulation of Hexanal, (E)-2-nonenal, and (E)-2-hexenal. Additionally, the expression levels of ADH and AAT genes, located downstream in the fatty acid metabolism pathway, were positively correlated with the accumulation of substances like (Z)-2-pentenol and 6-methylhept-4-en-1-yl 3-methylbutanoate. These findings provide a foundation for further research on the mechanisms through which fatty acid metabolism pathway genes regulate chili fruit aroma formation.