Grapevine rootstocks differentially affect ripening inception and auxin-related genes of Cabernet-Sauvignon berries

Abstract

In modern viticulture, grafting commercial grapevine varieties on rootstocks is a common practice that is required to confer resistance to various biotic and abiotic stresses. The use of rootstocks to gain these essential resistance traits is also known to influence grape berry development and quality, despite the underlying mechanisms remain poorly understood. In grape berries, the onset of ripening (véraison) is regulated by a complex network of mobile signals including hormones such as auxins, ethylene, abscisic acid and brassinosteroids. Recently M4, a new grapevine rootstock, has been developed based on its enhanced tolerance to water stress. The present study aimed at dissecting the effect of M4 and the widely used 1103P rootstocks on the transcriptome of Cabernet Sauvignon (CS) berry development from pre-véraison to harvest. Physical and biochemical parameters showed that CS berries reach véraison faster when grafted onto M4 than on 1103P. Expression studies performed by deep sequencing and by quantitative real-time PCR analyses on berry tissues revealed significant differences in the transcriptome profiles between graft combinations at all analysed stages. Considering the important role of auxin in grape berry development, we focus on the transcriptional regulation of auxin-related genes and their effect in determining the shift in maturation between the two graft combinations. A genomic and transcriptomic characterization of grapevine gene families involved in auxin metabolism and signalling including conjugation (GH3), transport (PIN and PIN-like) and action (ARF and AUX/IAA) of auxin was carried out. The data suggest that several members are actively involved in the control of berry development and might be critical in determinant the shift in maturation between the two graft combinations.