A MADS-box transcription factor from grapevine, VvMADS45, influences seed development

Grape is one of the most economically important fruits worldwide, and seedless fruit is a main target in grape breeding. The MADS-box genes encode a large family of transcription factors in higher plants, and serve various developmental roles including flower, fruit and seed development. However, little is known about function of MADS-box genes in grapevine, especially related to seed development. Here, we characterized a role for the grapevine MADS-box gene, VvMADS45, in seed development. Heterologous expression of VvMADS45 (VvMADS45-OE) in tomato resulted in larger flowers, fruit and seeds. In contrast, disruption of a tomato homolog of VvMADS45 (SlAGL104-KO) resulted in smaller flowers, fruit and seeds. In addition, both VvMADS45-OE and SlAGL104-KO lines produced fewer seeds than control. The fraction of pollen grains that appeared abnormal or failed to rehydrate was greater in VvMADS45-OE lines than in non-transgenic control plants, while relatively few abnormal pollen grains were formed in SlAGL104-KO lines. Expression of several genes related to flower, fruit and seed development was altered in both VvMADS45-OE and SlAGL104-KO lines. These results revealed that VvMADS45 participates in flower, fruit and seed development, especially seed development, which may provide new insight into the genetic basis of seedlessness in grapes. Heterologous expression of grapevine VvMADS45 in tomato increases the size of flowers, fruit and seeds, and decreases seed number, while disruption of the tomato homolog of this gene, SlAGL104, decreases the size of the flowers, fruit, and seeds, as well as seed number.