Background: H₂S is proved to be functioning as a signaling molecule in an array of physiological processes in the plant and animal kingdom. However, the H₂S synthesis pathway and the responses to cold conditions remain unclear in postharvest mushroom.

Results: The biosynthesis of H₂S in the Agaricus bisporus mushroom tissues exhibited an increasing tendency during postharvest storage and was significantly triggered by cold treatment. The cystathionine γ-lyase (AbCSE) and cystathionine β-synthase (AbCBS) genes were cloned and proved responsible for H₂S biosynthesis. Furthermore, transcriptional and posttranscriptional regulation of AbCSE and AbCBS were crucial for the enzyme activities and subsequent H₂S levels. However, the AbMST was not involved in this process. Moreover, the AbCSE and AbCBS genes displayed low identity to the characterized genes, but typical catalytic domains, activity sites, subunit interface sites, and cofactor binding sites were conserved in the respective protein sequences, as revealed by molecular modeling and docking study. The potential transcription factors responsible for the H₂S biosynthesis in cold conditions were also provided.

Conclusions: The H₂S biosynthetic pathway in postharvest mushroom was unique and distinct to that of other horticultural products.