The RING-H2 gene LdXERICO plays a negative role in dormancy release regulated by low temperature in Lilium davidii var. unicolor.

Dormancy regulation is the basis of the sustainable development of the lily industry. Therefore, basic research on lily dormancy is crucial for innovation in lily cultivation and breeding. Previous studies revealed that dormancy release largely depends on abscisic acid (ABA) degradation. However, the key genes and potential regulatory network remain unclear. We used exogenous ABA and ABA inhibitors to elucidate the effect of ABA on lily dormancy. Based on the results of weighted gene coexpression network analysis (WGCNA), the hub gene LdXERICO was identified in modules highly related to endogenous ABA, and a large number of coexpressed genes were identified. LdXERICO was induced by exogenous ABA and expressed at higher levels in tissues with vigorous physiological activity. Silencing LdXERICO increased the low-temperature sensitivity of bulblets and accelerated bulblet sprouting. LdXERICO rescued the ABA insensitivity of xerico mutants during seed germination in Arabidopsis, suggesting that it promotes seed dormancy and supporting overexpression studies on lily bulblets. The significant increase in ABA levels in transgenic Arabidopsis expressing LdXERICO indicated that LdXERICO played a role by promoting ABA synthesis. We generated three transgenic lines by overexpressing LdICE1 in Arabidopsis thaliana and showed that, in contrast to LdXERICO, LdICE1 positively regulated dormancy release. Finally, qRT-PCR confirmed that LdXERICO was epistatic to LdICE1 for dormancy release. We propose that LdXERICO, an essential gene in dormancy regulation through the ABA-related pathway, has a complex regulatory network involving temperature signals. This study provides a theoretical basis for further exploring the mechanism of bulb dormancy release.