The CONSTANS/CONSTANS-LIKE (CO/COL) gene family plays important roles in plants flowering and stress response. In this study, two variants of the MiCOL14B gene were identified from two different mango cultivars; they were designated as MiCOL14B-GQ and MiCOL14B-JH, which exhibited significant differences in sequence and B-box domain. Both genes were expressed in various tissues of mango, localized in the nucleus, and responsive to drought and salt stress. In transgenic Arabidopsis thaliana, MiCOL14B-GQ delayed flowering, while MiCOL14B-JH promoted flowering. This phenotypic divergence stemmed from their molecular regulatory specificity. Yeast one-hybrid (Y1H) and dual-luciferase reporter assays demonstrated that both variants directly bind to the promoters of florigen genes (MiFTs), with MiCOL14B-GQ repressing their transcription and MiCOL14B-JH enhancing it. Altered expression levels of MiFTs in the roots of transgenic mango further validated this mechanism. Moreover, both MiCOL14B-GQ and MiCOL14B-JH improved stress tolerance under drought and salt conditions in transgenic A. thaliana as well as in transgenic mango roots. These variants significantly increased stress tolerance by increasing proline (Pro) content and superoxide dismutase (SOD) activity, while reducing malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) accumulation. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays revealed that MiCOL14B-GQ and MiCOL14B-JH interact with several stress-related proteins. This study demonstrates for the first time the functional effects of sequence variation in the MiCOL14B gene on flowering and stress responses, providing valuable genetic resources for mango molecular breeding.

The SKP1 gene is an important component of the SCF (SKP1-Cullin1-F-box) complex and serves as a bridge connecting the F-box and Cullin1 genes (F-box-SKP1-Cullin1). The pattern of S-RNase being ubiquitously labelled by the SCF complex and degraded by the 26S protease accounts for the bulk of the available self-incompatibility studies. In this study, 15 ClSKP1s from the ‘Xiangshui’ lemon genome and ubiquitome exist in the same SKP1 conserved domain (CD) as SKP1s in other species. The qPCR results showed that SKP1-6 and SKP1-14 have tissue expression patterns specific for expression in pollen. In addition, SKP1-6 and SKP1-14 in the stigma, style and ovary were significantly upregulated after self-pollination compared to those after cross-pollination. A subcellular location showed that SKP1-6 and SKP1-14 were located in the nucleus. In addition, yeast two-hybrid (Y2H) assays, bimolecular fluorescence complementation (BiFC) and luciferase complementation imaging (LCI) assays showed that SKP1-6 interacted with F-box1, F-box33, F-box34, F-box17, F-box19, Cullin1-2 and 26S proteasome subunit 4 homolog A (26S PS4HA). SKP1-14 interacted with F-box17, F-box19, F-box35, Cullin1-2 and 26S PS4HA. The interaction of Cullin1-2 and the F-box with SKP1 as a bridge was verified by a yeast three-hybrid experiment. The ability of S₃-RNase to inhibit pollen and pollen tube growth and development was assessed using in vitro pollen co-culture experiments with recombinant S₃-RNase proteins. Overall, this study provides important experimental evidence and theoretical basis for understanding the mechanism of self-incompatibility in plants by revealing the key role of the SCF complex in ‘Xiangshui’ lemon, which is bridged by ClSKP1-6, in self-incompatibility. The results of this study are of great significance for the future in-depth exploration of the molecular mechanism of the SCF complex and its wide application in the self-incompatibility of plants.