Overexpression of SEPALLATA3-like Gene SnMADS37 Generates Green Petal-Tip Flowers in Solanum nigrum

The <i>SEPALLATA3</i> (<i>SEP3</i>)-like MADS-box genes play crucial roles in determining petal identity and development in the petunia and tomato of Solanaceae. <i>Solanum nigrum</i> is a self-pollinating plant in the Solanaceae family, and produces white flowers. However, the mechanisms controlling the transition from green to white petals during flower development remain poorly understood. In this study, we isolated a flower-specific <i>SEP3</i>-like gene, <i>SnMADS37</i>, from <i>S. nigrum</i>, and investigated its potential role in chlorophyll metabolism during petal development. Our results show that quantitative RT-PCR analysis demonstrates that <i>SnMADS37</i> is exclusively expressed in petals and stamens during early floral bud development. Overexpression of <i>SnMADS37</i> clearly enhanced the number of petals, promoting the formation of additional petal-like tissues in stamens and extra organs in some fruits. Moreover, fully opened transformed petals exhibited notable chlorophyll accumulation at their tips and veins, whereas silencing of <i>Snmads37</i> clearly inhibited petal expansion and reduced green pigmentation in early flower buds. Additionally, the transformed green petals exhibited distinct conical epidermal cells in the green regions, similar to wild type (WT) petals. Our results demonstrate that <i>SnMADS37</i> plays a critical role in regulating petal identity, expansion, and chlorophyll metabolism during petal development. These findings provide new insights into the functional diversification of <i>SEP3</i>-like MADS-box genes in angiosperms.