A phylogenetic and transcriptomic study of the β-1,3-glucanase family in tomato identifies candidate targets for fruit improvement

Abstract

Tomato, Solanum lycopersicum, is one of the most cultivated fruits. However, between one-quarter and half of their production is lost during transport and storage. Modifications in cell walls, and specifically pectin composition, delay fruit softening but, so far, the impact of callose metabolism in this process has not been investigated. Callose accumulates in cell walls around plasmodesmata to modify symplasmic transport. It also plays a role in reinforcing cell walls in response to bruising or pathogen invasion. The aim of this work is to identify cell wall {beta}-1,3-glucanases expressed in tomato fruit that can be used as targets to modify callose accumulation during ripening. A phylogenetic analysis identified fifty candidate {beta} -1,3-glucanases in tomato distributed in three clusters (, {beta} and {gamma}) with evolutionary relations previously characterised in the model Arabidopsis thaliana. Analysis of tomato microarray data indicates different regulatory patterns: the expression of a subset of enzymes in cluster decreased during ripening, while enzymes in cluster {beta} and {gamma} displayed higher expression in white-red stages. qRT-PCR experiments confirm the differential regulation of enzymes in different clusters suggesting evolutionary divergences that correlate with differences in their predicted localization and function. The potential to exploit this information in the selection of targets to modify cell walls and fruit development is discussed.