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

## TL;DR

This study shows that thiamine biosynthesis genes in common beans help resist Fusarium wilt disease, offering new strategies for crop protection.

## Contribution

The study identifies and characterizes thiamine biosynthesis genes in common bean and demonstrates their role in conferring resistance to Fusarium wilt.

## Key findings

- Resistant bean genotypes show higher expression of thiamine biosynthesis genes and accumulate more thiamine than susceptible ones.
- Overexpression of the PvTPK gene in susceptible plants increases thiamine levels and improves resistance to Fusarium wilt.
- Exogenous thiamine application reduces wilt severity and activates defense-related genes within 7 days.

## Abstract

Fusarium wilt is a devastating soil-borne disease that can reduce common bean yields by up to 50% in severely affected regions worldwide. In this study, five key thiamine biosynthetic genes were identified in common bean, all showing evolutionary conservation across plant species. These genes exhibited distinct activity in different plant organs. Upon infection, resistant genotypes displayed 2–3 fold higher expression of thiamine biosynthetic genes and accumulated significantly greater amounts of thiamine and its active form ThDP compared with susceptible genotypes. Enhancement of the critical gene PvTPK in susceptible plants by biotechnology increased thiamine levels by about 1.8-fold and conferred improved resistance. Likewise, exogenous application of 50 mM thiamine induced defense-related genes and reduced wilt severity within 7 days. These findings demonstrate that natural thiamine metabolism plays a pivotal role in defense against Fusarium wilt and that both genetic enhancement and exogenous thiamine supplementation provide sustainable strategies to protect bean harvests from this disease.

Fusarium wilt, caused by Fusarium oxysporum f. sp. phaseoli (Fop), is a major constraint to global common bean (Phaseolus vulgaris 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 PvTHI1-1 and PvTHIC 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 PvTPK 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 Agrobacterium rhizogenes-mediated transformation demonstrated that overexpression of PvTPK 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.