Transcription factor CaPHR3 enhances phosphate starvation tolerance by up-regulating the expression of the CaPHT1;4...

Plants frequently encounter phosphate (Pi) starvation due to its scarce availability in soil, necessitating an adaptive phosphate starvation response (PSR). This study explores this adaptation in pepper (Capsicum annuum L.) under low-Pi stress, focusing on the PHOSPHATE STARVATION RESPONSE (PHR) gene family. We observably halted shoot growth but promoted root elongation in pepper seedlings under low-Pi conditions, significantly impacting regulatory networks. Our research identified 13 PHR transcription factors in pepper, particularly noting that CaPHR3 rapidly up-regulates in response to low-Pi stress. Overexpressing CaPHR3 in Arabidopsis thaliana enhanced Pi starvation tolerance by modulating PSR-related genes and mitigated hypersensitivity in the Atphr1phl1 double mutant. Furthermore, CaPHR3 binds to the P1BS motif in the pepper PHOSPHATE TRANSPORTER 1;4 (PHT1;4) promoter to boost its expression under Pi deficiency. This activation increased Pi uptake and starvation tolerance when overexpressed. Overall, we pinpointed key players in the PSR mechanism through the CaPHR3-CaPHT1;4 pathway, contributing significantly to our understanding of Pi homeostasis and adaptive strategies in pepper under Pi-deficient conditions.