Genome-wide characterization of MADS-box genes and their roles in axillary bud development in tobacco.

A total of 118 NtMADS-box genes were identified in tobacco, revealing their potential roles in axillary bud development. Preliminary overexpression analysis indicated that NtMADS91 promotes axillary bud development. MADS-box transcription factors are core regulators of plant development, but their functions in axillary bud development in Nicotiana tabacum L. have not been systematically elucidated. In this study, 118 NtMADS-box genes were identified from the tobacco genome. Phylogenetic analysis classified them into type I (comprising the Mα and Mγ subfamilies) and type II (comprising the MIKC* and MIKCC clades). Promoter analysis revealed that cis-acting elements were predominantly associated with light and hormone responses. RNA-seq analysis of axillary buds after topping identified 60 differentially expressed NtMADS-box genes, from which 12 candidate genes with significant expression changes were selected. Tissue-specific qRT-PCR revealed that seven of these genes were preferentially expressed in axillary buds, with members of the SOC1 and SVP subfamilies accounting for the majority. Exogenous application of abscisic acid and the strigolactone analog GR24 significantly suppressed the expression of most candidate genes, including NtMADS91. The preliminary overexpression analysis suggested that NtMADS91 may promote axillary bud growth, increasing both the number and length of axillary buds. This study lays a foundation for future dissection of the regulatory mechanisms of the NtMADS-box gene family in axillary bud development and provides promising candidate genes for research related to tobacco axillary bud development.