Identification of pivotal genes associated with sugar and organic acid metabolism during Prunus mume fruit ripening via metabolomic and transcriptomic analyses
The fruit of Prunus mume has been one of the most popular functional foods and Chinese traditional medicines for centuries. Sugars and organic acids determine flavor, nutritional and medicinal quality of P. mume fruit. This study examined changes in the metabolism of sugars and organic acids at four stages of fruit ripening, by which sucrose and citrate were identified as the predominant sugar and organic acid, respectively. Abscisic acid (ABA) revealed significant positive correlation with citrate and sucrose accumulation, as also demonstrated by the coexression tendency. During ripening, the increase of sucrose was significantly associated with up-regulation of SPS (LOC103341128), SUS (LOC103323057) and GLGC (LOC103320871), and with down-regulation of three INVs (LOC 103337231, LOC 103333352 and LOC103341755). For citrate, upregulation of PEPC (LOC103318857) and CS (LOC103328745) in citrate synthesis could significantly accelerate the citrate accumulation, while downregulation of NADP-IDH (LOC103340345) and GS (LOC103321068 and LOC103338669) could be responsible for reduction of citrate degradation. Therefore, the accumulation of sucrose and citrate depended mainly on both strong synthesis and weak degradation. In addition, 328 differentially expressed transcription factors and 97 transport carriers might be responsible for the regulation and transportation of sugars and organic acids. Protein-protein interactome analysis implied a highly complex metabolism network in which AP2 might be one of the central nodes. These findings contribute to clarify the metabolism of sugars and organic acids in P. mume.