Isolation and characterization of six peach cDNAs encoding key proteins in organic acid metabolism and solute accumulation: involvement in regulating peach fruit acidity

Abstract

As in many other fleshy fruits, the predominant organic acids in ripe peach (Prunus persica (L.) Batsch) fruit are malic and citric acids. The accumulation of these metabolites in fruit flesh is regulated during fruit development. Six peach fruit-related genes implicated in organic acid metabolism (mitochondrial citrate synthase; cytosolic NAD-dependent malate dehydrogenase, and cytosolic NADP-dependent isocitrate dehydrogenase) and storage (vacuolar proton translocating pumps: one vacuolar H+-ATPase, and two vacuolar H+-pyrophosphatases) were cloned. Five of these peach genes were homologous to genes isolated from fruit in other fleshy fruit species. Phylogenetic and expression analyses suggested the existence of a particular vacuolar pyrophosphatase highly expressed in fruit. The sixth gene was the first cytosolic NAD-dependent malate dehydrogenase gene isolated from fruit. Gene expression was studied during the fruit development of two peach cultivars, a normal-acid (Fantasia) and a low-acid (Jalousia) cultivar. The overall expression patterns of the organic acid-related genes appeared strikingly similar for the two cultivars. The genes involved in organic acid metabolism showed a stronger expression in ripening fruit than during the earlier phases of development, but their expression patterns were not necessarily correlated with the changes in organic acid contents. The tonoplast proton pumps showed a biphasic expression pattern more consistent with the patterns of organic acid accumulation, and the tonoplast pyrophosphatases were more highly expressed in the fruit of the low-acid cultivar during the second rapid growth phase of the fruit.

Qualidade de pêssegos cv. "Eldorado" tratados com aminoetoxivinilglicina e ethephon e armazenados em atmosfera controlada

“…"Stark Red Gold" tratadas com AVG. A relação entre o etileno e o metabolismo dos ácidos orgânicos ainda não foi devidamente elucidada, porém ETIENNE et al (2002) verificaram que a expressão de cDNAs para proteínas-chave do metabolismo dos ácidos orgânicos é maior durante o amadurecimento, sendo concomitante com o aumento na produção de etileno. Os frutos armazenados em AC com 2,0kPa de O 2 + 5,0kPa de CO 2 apresentaram maior acidez titulável ao final de quatro dias a 15°C (Tabela 3).…”

“…Os frutos armazenados em AC com 2,0kPa de O 2 + 5,0kPa de CO 2 apresentaram maior acidez titulável ao final de quatro dias a 15°C (Tabela 3). Provavelmente, a redução na taxa respiratória dos frutos armazenados nessa condição (Tabela 1) resultou em menor consumo dos ácidos orgânicos no ciclo dos ácidos tricarboxílicos (ETIENNE et al, 2002).…”

Armazenamento de pêssegos cv. "Granada" em atmosfera controlada, visando ao transporte a longas distâncias

“…Esse resultado deve-se, em parte, a baixa taxa respiratória desses frutos (Tabela 1), que deve ter reduzido o consumo dos ácidos orgânicos pelo ciclo dos ácidos tricarboxílicos (ETIENNE et al, 2002). Após quatro dias a 20ºC, a acidez titulável dos frutos foi semelhante, independentemente dos tratamentos (Tabela 3).…”

Citrus plastid-related gene profiling based on expressed sequence tag analyses

“…A fruit-specific preference in expression for lipoxygenase C and isocitrate dehydrogenase was detected in the survey for organ-specific sequences. Both enzymes corroborate a fruit-specific function, since lipoxygenase C is linked with the development of volatile compounds, carotenoids and jasmonate responses in fruit (Rangel et al, 2002), and plastid isocitrate dehydrogenase activity has been demonstrated to be associated with inorganic pyrophosphatase and accumulation of organic acids in fruit (Etienne et al, 2002).…”