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.
