NAC domain gene VvNAC26 interacts with VvMADS9 and influences seed and fruit development.

Grapevine (Vitis vinifera), as one of the potential gardening fruit have important economic and nutritional values. Seedless grapes are popular due to their convenience and excellent taste. As multifunctional proteins, the NAC family involves hormonal pathways, plant aging, and biological stress. However, reports of NAC affecting seed development are rare. Here, the role of grapevine VvNAC26 in regulating fruit ripening and seed size was characterized. There were remarkable differences in the expression of VvNAC26 in seeded and seedless grape varieties during ovule development. The exogenous transformation of VvNAC26 in tomato decreased the cells size of pericarp, fruits and seeds. In addition, led to cotyledon cells arranged more closely and narrowly and obviously decreased seeds at the fruit ripening stage. The tomato fruit of transgenic lines was darker red and underwent color conversion earlier than that of the wild type in the same period. Furthermore, the expression of some genes associated with hormone and fruit development was changed in overexpressed lines. Yeast two-hybrid and BiFC assays showed that VvNAC26 interacted with VvMADS9. In conclusion, these results suggest that VvNAC26 may regulate fruit and seed development by influencing multiple hormone pathways and interacting with VvMADS9 in grape. VvNAC26 may also serve as a candidate for future understanding of the potential regulatory mechanism of seed development and molecular breeding in grapevine.