The strawberry (Fragaria x ananassa) fruit-specific rhamnogalacturonate lyase 1 (FaRGLyase1) gene encodes an enzyme involved in the degradation of cell-wall middle lamellae

Abstract

Pectins are essential components of primary plant cell walls and middle lamellae, and are related to the consistency of the fruit and its textural changes during ripening. In fact, strawberries become soft as the middle lamellae of cortical parenchyma cells are extensively degraded during ripening, leading to the observed short post-harvest shelf life. Using a custom-made oligonucleotide-based strawberry microarray platform, a putative rhamnogalacturonate lyase gene (FaRGlyase1) was identified. Bioinformatic analysis of the FaRGlyase1 sequence allowed the identification of a conserved rhamnogalacturonate lyase domain, which was also present in other putative RGlyase sequences deposited in the databases. Expression of FaRGlyase1 occurred mainly in the receptacle, concurrently with ripening, and it was positively regulated by abscisic acid and negatively by auxins. FaRGLyase1 gene expression was transiently silenced by injecting live Agrobacterium cells harbouring RNA interference constructs into fruit receptacles. Light and electron microscopy analyses of these transiently silenced fruits revealed that this gene is involved in the degradation of pectins present in the middle lamella region between parenchymatic cells. In addition, genetic linkage association analyses in a strawberry-segregating population showed that FaRGLyase1 is linked to a quantitative trait loci linkage group related to fruit hardness and firmness. The results showed that FaRGlyase1 could play an important role in the fruit ripening-related softening process that reduces strawberry firmness and post-harvest life.