Genome-Wide Identification and Expression Analyses of the MADS-Box Gene During Flowering in Primulina huaijiensis

<i>Primulina huaijiensis</i> is a promising candidate for eco-bottle flowers, yet the genes related to flowering remain unexplored despite the availability of genomic data for several years. <i>MADS-box</i> genes constitute a large family of transcription factors that play crucial roles in plant growth and development, particularly in flower development. In this study, we identified 84 <i>MADS-box</i> genes (<i>PhuMADS</i>) in <i>P. huaijiensis</i> genome and analyzed their evolution and expression profiles to gain insights into the flowering mechanism. The 84 genes constitute 29 type I and 55 type II <i>MADS-box</i> genes. Phylogenetic analysis further classified them into 17 subfamilies, which were randomly distributed across 18 chromosomes and four scaffolds. <i>PhuMADS</i> genes exhibit a range of 1 to 12 exons and share conserved motifs. Segmental duplication was found to be the primary driver of <i>PhuMADS</i> gene family expansion, with duplicated gene pairs undergoing purifying selection. <i>Cis</i>-acting elements analysis revealed <i>PhuMADS</i> promoters harbor abiotic stress-, hormone-, light-, and growth-related motifs, implicating roles in development and environmental adaptation in <i>P. huaijiensis</i>. RNA-seq showed distinct expression patterns of <i>PhuMADS</i> genes among different tissues or developmental stages. The results of qRT-PCR analysis of selected genes further validated the RNA-seq findings, suggesting these genes may exert distinct functional roles during floral development. This study laid a theoretical foundation for further functional studies of the <i>MADS-box</i> genes in <i>P. huaijiensis</i>.