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.

The grapevine homeobox gene VvHB58 influences seed and fruit development through multiple hormonal signaling pathways.

BACKGROUND: The homeobox transcription factor has a diversity of functions during plant growth and development process. Previous transcriptome analyses of seed development in grape hybrids suggested that specific homeodomain transcription factors are involved in seed development in seedless cultivars. However, the molecular mechanism of homeobox gene regulating seed development in grape is rarely reported. RESULTS: Here, we report that the grapevine VvHB58 gene, encoding a homeodomain-leucine zipper (HD-Zip I) transcription factor, participates in regulating fruit size and seed number. The VvHB58 gene was differentially expressed during seed development between seedless and seeded cultivars. Subcellular localization assays revealed that the VvHB58 protein was located in the nucleus. Transgenic expression of VvHB58 in tomato led to loss of apical dominance, a reduction in fruit pericarp expansion, reduced fruit size and seed number, and larger endosperm cells. Analysis of the cytosine methylation levels within the VvHB58 promoter indicated that the differential expression during seed development between seedless and seeded grapes may be caused by different transcriptional regulatory mechanisms rather than promoter DNA methylation. Measurements of five classic endogenous hormones and expression analysis of hormone-related genes between VvHB58 transgenic and nontransgenic control plants showed that expression of VvHB58 resulted in significant changes in auxin, gibberellin and ethylene signaling pathways. Additionally, several DNA methylation-related genes were expressed differentially during seed development stages in seedless and seeded grapes, suggesting changes in methylation levels during seed development may be associated with seed abortion. CONCLUSION: VvHB58 has a potential function in regulating fruit and seed development by impacting multiple hormonal pathways. These results expand understanding of homeodomain transcription factors and potential regulatory mechanism of seed development in grapevine, and provided insights into molecular breeding for grapes.