Transcriptomic and functional analysis reveals that VvSAUR43 may be involved the elongation of grape berries

The overall shape of grape (Vitis vinifera) berries is an important quality trait. The application of gibberellin (GA3) will elongate fruit, however, the molecular mechanisms involved in this response are unknown. Results of the present study indicated that the application of GA3 promoted the levels of endogenous IAA and IAA-AsP. In regard to cell development, compared with the control group, GA3 treatment contributing to lengthen the longitudinal elongation of cell and the fruit shape index. Gene Ontology (GO) enrichment analysis show that DEGs were mainly enriched in the cell periphery, external encapsulating structure, and cell wall of cellular components. KEGG analysis revealed that the GA3 treatment positively regulated the signal transduction pathways for auxin, especially IAA, and brassinosteroid (BR). Notably, the IAA signal transduction pathway accounted for the largest proportion of the assigned genes, being 50%, 60%, and 61% of the total number of DEGs in the T6h vs CK6h, T24h vs CK24h, and T24h vs T6h comparison, respectively. Among the responding genes, Small Auxin-Upregulated RNA (SAUR) genes responded rapidly and were significantly enriched. Phylogenetic analysis of the SAUR gene family indicated that SAUR genes in grape and Arabidopsis have high homology. Furthermore, VvSAUR43 gene overexpressed in tomato and tobacco produce elongated fruit in tomato, leaf and the shape index of silique are also significantly up-regulated in tobacco transgenic plants. The study revealed that IAA plays a major role in the response to the GA3 treatment, and that increased IAA levels enhance VvSAUR expression, ultimately resulting in an elongated fruit shape. Our study provides new insights into the molecular mechanism responsible for the effect of GA3 on fruit shape.