<i>CmWOX2</i> modulates somatic embryogenesis in Chinese chestnut (<i>Castanea mollissima</i> Blume)

Chinese chestnut (<i>Castanea mollissima</i> Blume) is distinguished by its remarkable nut quality and robustness against disease and environmental stressor. However, its somatic embryogenesis process is notably slow, presenting a significant bottleneck in its cultivation. This study focuses on the <i>WUSCHEL</i> (<i>WUS</i>)<i>-related homeobox 2 gene</i> (<i>WOX2</i>), a member of <i>WOX</i> transcription factors gene family, known for its critical role in the somatic embryo development of Arabidopsis. We have identified and explored the function of a <i>WOX2</i> homolog in Chinese chestnut, termed <i>CmWOX2</i>, in the context of somatic embryogenesis. Our analysis revealed seven <i>WUS</i> gene family members in the species, with <i>CmWOX2</i> being uniquely upregulated in callus. Our experiments demonstrated that suppression of <i>CmWOX2</i> expression diminishes somatic embryo production, whereas its overexpression enlarges the embryonic callus diameter. Notably, <i>CmWOX2</i> expression levels are threefold higher in varieties with high embryogenic competence, such as 'Jingshuhong' and 'Huaihuang', compared to those with lower competence, including 'Jiujiazhong' and 'Shandonghongli'. These findings underscored the pivotal role of <i>CmWOX2</i> in the initial stages of Chinese chestnut somatic embryogenesis, highlighting its potential as a target for enhancing somatic embryogenesis in this species.