TLP gene family in Rehmannia glutinosa: RgTLP1 functions in Fusarium oxysporum resistance.

Abstract

Rehmannia glutinosa Libosch. is a medicinal and edible plant whose tuberous roots are widely used for clinical and food purposes, yet its production is severely threatened by root rot caused by Fusarium oxysporum (FO). Thaumatin-like proteins (TLPs) are plant defense proteins with antifungal activity, but their roles in R. glutinosa defense against this disease remain unexplored. This study identified 21 RgTLP genes through integrated transcriptome and genome analysis and found that the family resolved into three clades, with RgTLP1 clustering among functionally characterized defense-related TLPs. Eight RgTLPs showed root-preferential expression, of which five exhibited sustained induction upon FO infection; transient overexpression of these five members in R. glutinosa root slices significantly reduced FO damage, with RgTLP1 showing the strongest protective phenotype. RgTLP1 localized to the apoplast, exhibited β-1,3-glucanase activity, inhibited FO growth in a dose-dependent manner in vitro, and enhanced FO resistance in three independent transgenic N. benthamiana lines overexpressing RgTLP1, accompanied by increased antioxidant enzyme activities and reduced oxidative damage. These findings indicate that RgTLP1 contributes to FO resistance through both antifungal activity and enhancement of host antioxidant capacity, suggesting its potential as a target for the genetic improvement of FO resistance in R. glutinosa.