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Phosphorus deficiency is one of the major abiotic stresses affecting plant growth. Plants respond to the persistent deficiency of phosphate (Pi) by coordinating the expression of genes involved in alleviation of the stress. The high-affinity Pi transporters are among the major molecular determinants that are activated during Pi stress. In this study, using three reporter genes (green fluorescent protein, luciferase, and beta-glucuronidase) regulated by two Pi transporter promoters, we have carried out an extensive analysis of transcriptional and spatial regulation of gene expression. Activation of the genes was rapid, repressible, and specific in response to changes in Pi availability. The phytohormones auxin and cytokinin suppressed the expression of the reporter gene driven by the AtPT1 promoter, and that of the native gene, suggesting that hormones may be involved in regulation of some component(s) of Pi starvation response pathway. These studies also provide molecular evidence for a potential role of high-affinity Pi transporters in mobilizing Pi into reproductive organs. The results suggest that members of the Pi transporter family may have similar but nonredundant functions in plants.
Karthikeyan et al. (Sun,) studied this question.