Genome-Wide Analysis of the Thiamine Biosynthesis Gene Families in Common Bean Reveals Their Crucial Roles Conferring Resistance to Fusarium Wilt

Fusarium wilt, caused by <i>Fusarium oxysporum</i> f. sp. <i>phaseoli</i> (Fop), is a major constraint to global common bean (<i>Phaseolus vulgaris</i> L.) production. Thiamine (vitamin B1), an essential coenzyme in plant metabolism, has recently emerged as a potential regulatory factor in plant defense. Here, we performed a comprehensive genome-wide analysis of thiamine biosynthesis-related genes in common bean and elucidated their roles in resistance to Fusarium wilt. Five key thiamine biosynthetic genes were identified and characterized, showing conserved functional domains and evolutionary conservation across species. Expression profiling revealed tissue-specific patterns, with <i>PvTHI1-1</i> and <i>PvTHIC</i> being highly expressed in reproductive and photosynthetic organs, with their relative expression levels 0.28–0.57 higher than other members in the same tissue, while <i>PvTPK</i> maintained a basal expression level in the roots. Upon Fop infection, resistant genotypes exhibited significantly higher expression of thiamine biosynthetic genes and greater accumulation of endogenous thiamine and its derivatives than susceptible ones. Functional analysis using <i>Agrobacterium rhizogenes</i>-mediated transformation demonstrated that overexpression of <i>PvTPK</i> enhanced thiamine metabolism and conferred resistance in susceptible genotypes. Similarly, exogenous application of thiamine upregulated biosynthetic genes and improved disease resistance. Together, these results reveal that thiamine biosynthesis is intricately linked to Fusarium wilt resistance and that both genetic and biochemical manipulation of thiamine pathways can enhance disease tolerance. This study provides new insights into thiamine-mediated plant immunity and establishes a foundation for its application in the control of Fusarium wilt in common bean.