Precision control of maize stalk rot by cysteine-functionalized nanocarriers via the ZmLHT1 amino acid transporter

Maize stalk rot (MSR) caused by Fusarium graminearum (F. graminearum) is a destructive soil-borne disease. Conventional fungicides, including tebuconazole (Teb), exhibited poor systemic translocation and basipetal transport, and seed coating provided only short-term protection, resulting is low efficacy. Here, we developed a cysteine-functionalized polysuccinimide nanocarrier loaded with tebuconazole (Teb@PCA), which showed a lower EC₅₀ against F. graminearum and pH-responsive release compared with tebuconazole suspension concentrate (Teb SC). In maize, foliar-applied Teb@PCA was able to translocate to roots with a peak concentration of 0.082 mg/kg, whereas Teb SC was not detected, and reduced stem lesion area by 17.2% compared with the Teb SC treatment. Uptake of Teb@PCA was energy-dependent and inhibited by excess cysteine, and RNA sequencing (RNA-seq) indicated specific upregulation of ZmLHT1 in response to Teb@PCA. Heterologous expression of ZmLHT1 in yeast increased Teb@PCA accumulation by 2.1-fold, and a maize Zmlht1 loss-of-function mutant severely impaired Teb@PCA translocation to stems and roots. CoIP-MS suggested a possible association between ZmLHT1 protein and endomembrane trafficking proteins, including a putative beta adaptin like protein (K7WDG3). Collectively, these findings suggest that cysteine-functionalized nanocarriers leverage the endogenous transporter ZmLHT1 to facilitate phloem delivery of fungicides, offering a potential precision strategy for controlling vascular diseases such as maize stalk rot.