Loss of Phosphomannose Isomerase Impairs Growth, Perturbs Cell Wall Integrity, and Reduces Virulence of <i>Fusarium oxysporum</i> f. sp. <i>cubense</i> on Banana Plants
2023
Sayed Usman | Xinwei Ge | Yueqiang Xu | Qijian Qin | Jin Xie | Bin Wang | Cheng Jin | Wenxia Fang
<i>Fusarium oxysporum</i> f. sp. <i>cubense</i> tropical race 4 (<i>Foc</i> TR4) causes Fusarium wilt of banana, necessitating urgent measures to control this disease. However, the molecular mechanisms underlying <i>Foc</i> TR4 virulence remain elusive. Phosphomannose isomerase is a key enzyme involved in the biosynthesis of GDP mannose, an important precursor of fungal cell walls. In this study, two phosphomannose isomerases were identified in the <i>Foc</i> TR4 genome, of which only <i>Focpmi1</i> was highly expressed throughout all developmental stages. Generated null mutants in <i>Foc</i> TR4 showed that only the Δ<i>Focpmi1</i> mutant required exogenous mannose for growth, indicating that <i>Focpmi1</i> is the key enzyme involved in GDP mannose biosynthesis. The <i>Focpmi1</i> deficient strain was unable to grow without exogenous mannose and exhibited impaired growth under stress conditions. The mutant had reduced chitin content in its cell wall, rendering it vulnerable to cell wall stresses. Transcriptomic analysis revealed up- and down-regulation of several genes involved in host cell wall degradation and physiological processes due to the loss of <i>Focpmi1</i>. Furthermore, <i>Focpmi1</i> was also found to be crucial for <i>Foc</i> TR4 infection and virulence, making it a potential antifungal target to address the threats posed by <i>Foc</i> TR4.
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