Genome-wide analysis of the MADS-box gene family in mango and ectopic expression of MiMADS77 in Arabidopsis results in early flowering

Mango (Mangifera indica L.) is an important tropical fruit, and timely flowering and fruit setting are very important for mango production. The MADS-box gene family is involved in the regulation of flower induction, floral organ specification, and fruit development in plants. The identification and analysis of the MADS-box gene family can lay a foundation for the study of the molecular mechanism of flowering and fruit development in mango. In this study, 119 MiMADS-box genes were identified on the basis of genome and transcriptome data. Phylogenetic analysis revealed that these genes can be divided into two classes. Forty-one type I proteins were further divided into three subfamilies, and seventy-eight type II proteins were further classified into eleven subfamilies. Several pairs of alternative splicing genes were found, especially in the SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) subfamily. The MiMADS-box genes were distributed on 18 out of the 20 mango chromosomes. Cis-element analysis revealed many light-, stress-, and hormone-responsive elements in the promoter regions of the mango MiMADS-box genes. Expression pattern analysis revealed that these genes were differentially expressed in multiple tissues in mango. The highly expressed MiMADS77 was subsequently transformed into Arabidopsis, resulting in significant early flowering and abnormal floral organs. Yeast two-hybrid (Y2H) assays revealed that MiMADS77 interacts with several MiMADS-box proteins. In addition, we constructed a preliminary flowering regulatory network of MADS-box genes in mango on the basis of related studies. These results suggest that MiMADS77 genes may be involved in flowering regulation of mango.