Expression pattern of sugars and organic acids regulatory genes during watermelon fruit development

Abstract Watermelon has a fleshy fruit and that is the reason sugars and organic acids play a key role in taste formulation. So far, there is no comprehensive study in watermelon regarding accumulation and regulation of sugars and organic acids. To understand the behaviour of sugars and organic acids two watermelon inbred lines “203Z” (high sugar, low acid) and “SW” (low sugar, high acid) were used. The contents of each sugars and organic acids at three different developmental stages were measured via ion chromatography. Total 38 genes which were involved in sugars and organic acids metabolism and transport were screened out in watermelon fruit flesh. Genes for sugars and organic acids regulation and transport were highly expressed during watermelon fruit ripening. Fructose was observed as the main sugar and malic acid was the main organic acid in watermelon fruit flesh. WMFBPA-2 that is involved in fructose breakdown was positively and significantly correlated with fructose. Aluminum activated malate transporters and malate dehydrogenase genes were involved in malate regulation and degradation. It was concluded that WMALMT-3 may participate in the regulation of malic acid and its accumulation in vacuole during watermelon fruit development. WMCS was found to be associated with citric acid regulation. This study will improve our understanding and lay foundation to explore the function of these genes and improvement of watermelon fruit quality.