Changes in the mRNA abundance of FcXTH1 and FcXTH2 promoted by hormonal treatments of Fragaria chiloensis fruit

Chilean strawberry (Fragaria chiloensis) is a berry fruit with excellent organoleptic properties, however its fast softening limits its commercialization. Fruit softening is related to cell wall degradation and several related enzymes have been studied in strawberries, including xyloglucan endotransglycosylase/hydrolase (XTH). Two XTH genes have been identified in F. chiloensis, FcXTH1 and FcXTH2. FcXTH1 transcripts increased during fruit growth and softening, while FcXTH2 transcripts were high in vegetative tissues. XTH gene expression seems to be regulated in plants by different factors including hormones. To test their responsiveness, fruit were treated with auxin, abscisic acid, gibberellins and ethylene, and the expression of FcXTH isoforms was analysed. qPCR analysis revealed a significant variation in the expression of FcXTH genes after hormone treatments, showing an activator effect of auxins and GA₃ on both FcXTH genes, an inhibitory effect of ethylene on FcXTH2, and an inductive effect of ABA on FcXTH1 gene expression. FcXTH1 and FcXTH2 gene promoters were cloned and in silico analysed to reveal putative cis elements. Different regulatory elements responding to hormones were found in each promoter sequence. The changes in expression in response to hormone treatments are consistent with the regulatory elements described in the promoter sequences of FcXTH genes.