The Novel miRNA Is Involved in Grafting-Enhanced Phosphate Utilization and Phosphate Starvation Tolerance in Watermelon.

Watermelon () is a globally important Cucurbitaceae crop in which grafting is commonly used to improve stress tolerance and enhance nutrient utilization. However, the mechanism underlying grafting-enhanced nutrient assimilation remains unclear. Here, we demonstrate the possible involvement of a novel miRNA, , in grafting-enhanced phosphate-starvation tolerance via () suppression in watermelon. Transcript analyses revealed that the induction of expression was correlated with the downregulation of in squash-grafted watermelon under phosphate starvation. In addition, the differential expression of in various watermelon genotypes was consistent with their phosphate utilization efficiency. Furthermore, overexpression in Arabidopsis enhanced root growth and phosphate uptake under phosphate starvation and promoted inflorescence elongation under normal conditions. These results suggest that the axis is involved in phosphate starvation response as well as grafting-enhanced growth vigor and phosphate assimilation. The present study provides valuable insights for investigating long-distance signaling and nutrient utilization in plants.