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Involvement of vacuolar processing enzyme SlVPE5 in post-transcriptional process of invertase in sucrose accumulation in tomato

Wang, Ning, Duhita, Narendra, Ariizumi, Toru, Ezura, Hiroshi
Plant physiology and biochemistry 2016 v.108 pp. 71-78
RNA interference, amino acids, beta-fructofuranosidase, enzyme activity, flavor, fruit quality, fruiting, fruits, genes, humans, hydrolysis, messenger RNA, metabolites, proteins, proteomics, sucrose, tomatoes, vacuoles
Enhancing the flavor of fruits plays a fundamental role in improving fruit quality, and volatile compositions as well as acid and sugar accumulation are significant factors that have an impact on the acceptability of sensory responses by human beings. Vacuoles in plants not only function as cell compartments that store amino acids, sugars and other metabolites but also act as lytic organelles where vacuolar proteins are post-translationally processed into mature forms or degraded by the action of vacuolar processing enzyme (VPE). We have previously characterized VPE genes (SlVPE1-5) during fruit development in tomato and discovered that the VPE enzyme activity negatively interfered with sugar accumulation in mature fruits. Comparative proteomic analysis demonstrated that acid invertase was one of the molecular targets of SlVPE5, which is involved in the hydrolysis of sucrose. This study also showed that decreased VPE enzyme activity due to suppression of SlVPE5 by RNAi strategy (RNAi-SlVPE5) accompanied with decreased enzyme activity of acid invertase. Further, we identified the enzyme activity of acid invertase was not well correlated with mRNA levels in the RNAi-SlVPE5 line. These results suggest that SlVPE5 regulates post-transcriptional processing through de novo synthesis of the acid invertase protein to suppress enzyme activity, thereby eventually ensuring sucrose hydrolysis.