Differential expression and regulation of a neutral invertase encoding gene from peach (Prunus persica):: evidence for a role in fruit development

Studies on sucrose metabolism during fruit development have shown an important role of acidic (cell wall and vacuolar) invertases (EC 3.2.1.26) in determining fruit sink strength, final fruit growth and sugar accumulation. Little information is available on the role played by neutral (cytoplasmic) invertases on fruit and plant development. In this article, the expression of a gene encoding a neutral invertase (NI) isolated from peach (PpNI1) was studied in relation to sucrose metabolism and mesocarp development in two genotypes (cv. Springcrest and cv. Redhaven) differing for fruit growth, and sugar accumulation dynamics. Real-time reverse transcription-PCR expression analyses showed a differential regulation of the gene during development and a correlation with sucrose, and glucose and fructose mesocarp contents. Only one peak of expression of the gene was found in the early ripening cultivar Springcrest, characterised by a nearly monophasic growth of fruits, while two peaks could be detected in the mid-late ripening cv. Redhaven, displaying a classical biphasic double-sigmoidal fruit growth pattern. Furthermore, PpNI1 transcription appeared to be regulated in response to sugar signals only in the phase of fruit expansion coincident with the onset of sucrose accumulation. These findings point to a relationship between dynamics of fruit growth, sugar metabolism and sensing and the expression of a gene encoding a NI, suggesting a regulatory role in plant development for this class of enzymes.