Transcriptomic and biochemical insights into LOX pathway aroma biosynthesis during ripening of Ziziphus jujuba Mill. cv. Li

TL;DR

This study explores how the LOX pathway contributes to aroma development in jujube fruits during ripening, identifying key compounds and genetic factors involved.

Contribution

The study identifies key aroma compounds and genetic transcripts linked to the LOX pathway in jujube ripening, offering a genetic basis for quality improvement.

Findings

Hexanal, (E)-2-hexenal, and (E)-2-nonenal are key aroma compounds in ripening jujube fruits.

LOX enzyme activity increases significantly during ripening, while ADH activity remains low.

Transcriptome analysis identified 12 candidate genes associated with volatile compound accumulation.

Abstract

Aroma is a critical determinant of fruit quality, largely synthesized through the lipoxygenase (LOX) pathway. We hypothesized that the dynamic regulation of the LOX pathway during jujube fruit ripening governs the distinct evolution of its key aroma compounds. This study used HS-SPME coupled with GC–MS to profile aroma compounds in jujube during ripening. Semi-quantitative analysis revealed hexanal (1160–1870 μg/kg) and (E)-2-hexenal (1470–3180 μg/kg) as the most abundant aldehydes, followed by benzaldehyde and (E)-2-pentenal. Odor activity value (OAV) analysis identified hexanal, (E)-2-hexenal, and (E)-2-nonenal as the key aroma compounds. LOX enzyme activity increased from 277 U/g to 711 U/g during ripening, while ADH and AAT activities showed fluctuating trends. Transcriptome analysis revealed 12 candidate transcripts involved in aroma synthesis, with multivariate statistical analysis demonstrating coordinated changes in gene expression associated with volatile accumulation. Our findings verify the hypothesis that LOX pathway regulation drives aroma evolution during jujube ripening and provide a genetic foundation for targeted quality improvement in jujube fruits.

•Identified hexanal, (E)-2-hexenal, and (E)-2-nonenal as the key aroma compounds.•LOX activity increased 2.6-fold during ripening while ADH activity remained low.•Revealed a metabolic bottleneck at the ADH step, explaining the lack of alcohols.•Transcriptome analysis revealed 12 candidate transcripts regulating volatiles.•Multivariate analysis linked gene expression patterns with volatile accumulation.

Identified hexanal, (E)-2-hexenal, and (E)-2-nonenal as the key aroma compounds.

LOX activity increased 2.6-fold during ripening while ADH activity remained low.

Revealed a metabolic bottleneck at the ADH step, explaining the lack of alcohols.

Transcriptome analysis revealed 12 candidate transcripts regulating volatiles.

Multivariate analysis linked gene expression patterns with volatile accumulation.

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