Abstract

Plant vacuolar H+-ATPases (V-type H+-ATPases, VHA) and vacuolar H+-pyrophosphatases (V-PPase, VHP) are key proton pumps. VHA and VHP regulate cellular pH homeostasis and ion transport via the proton motive force across the vacuolar membrane, functioning in plant responses to environmental stress. However, they remain poorly characterized in melon, a high-value horticultural crop limited by environmental stresses. Here, a total of 24 V-type proton pump genes were identified from the whole melon genome. Collinearity analysis indicates that the proton pump genes are highly conserved in melons, although species-specific expansions and gene duplication events have been observed in the a and c subunits. Predictions of cis-acting elements in the promoters indicate that these genes are rich in regulatory elements associated with responding to plant hormones and abiotic stress. It was found that most genes were stimulated in response to salt treatment and exhibited consistent expression trends in both Elizabeth and Baishami. However, in Elizabeth, the responses of CmVHA-c″1 and CmVHA-a3 were slower, while the induction of CmVHP2;1 was almost undetectable in response to salt stress. This study provides a foundation for further functional analysis of proton pump genes and new insights into melon stress responses.

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