Molecular Characterization and Phylogenetic Analysis of MADS-Box Gene Associated with Stenospermocarpic Seedlessness in Muscadine Grapes.

Reduced expression of MADS-box gene () is responsible for stenospermocarpic seedlessness in bunch grapes. This study is aimed to characterize the orthologous gene () in native muscadine grapes () at the molecular level and analyze its divergence from other plants. The transcripts were found in all muscadine cultivars tested and highly expressed in berries while barely detectable in leaves. RT-PCR and sequencing of predicted ORFs from diverse grape species showed that transcripts were conservatively spliced. The encoded VroAGL11 protein contains highly conserved MADS-MEF2-like domain, MADS domain, K box, putative phosphorylation site and two sumoylation motifs. The muscadine VroAGL11 proteins are almost identical (99%) to that of seeded bunch cultivar, Chardonnay, except in one amino acid (A79G), but differs from mutant protein of seedless bunch grape, Sultanina, in two amino acids, R197L and T210A. Phylogenetic analysis showed that gene of muscadine and other species formed a separate clade than that of other eudicots and monocots. Muscadine grape cultivar "Jane Bell" containing the highest percentage of seed content in berry (7.2% of berry weight) had the highest expression, but almost none to nominal expression in seedless cultivars Fry Seedless (muscadine) and Reliance Seedless (bunch). These findings suggest that gene controls the seed morphogenesis in muscadine grapes like in bunch grape and can be manipulated to induce stenospermocarpic seedlessness using gene editing technology.