Cysteine-Mediated Root Growth Promotion in Strawberry () Induced by -Overexpressing .

Strawberry () is a globally important economic crop valued for its nutritional and commercial significance. However, its growth is frequently challenged by various biotic and abiotic stresses. To enhance strawberry root development and resilience, we engineered a NJAU4742 strain to overexpress the gene, which encodes a plant cell-wall-loosening protein known to facilitate fungal penetration and colonization. Strawberry seedlings treated with the -overexpressing NJAU4742 strain (S-OE) exhibited significant improvements in shoot and root fresh weights, root surface area, and number of root tips, showing 1.37- to 2.00-fold increases compared with the strawberry seedlings inoculated with the wild-type NJAU4742 (S-WT) and 2.00- to 3.44-fold increases compared with the uninoculated strawberry seedlings (S-CK). Field-emission scanning electron microscopy (SEM) of the S-OE roots revealed denser hyphal colonization. Transcriptome analysis of S-OE showed a decrease in genes related to defense and detoxification, while genes for cell-wall growth and hormone signaling increased, shifting focus from defense to growth. Metabolomic profiling identified cysteine as a key metabolite associated with induced growth, which was further validated through exogenous cysteine application experiments. This study highlights the potential of genetically enhanced for improving strawberry growth and provides new insights into root-microbe interactions and metabolite-mediated plant development.