Blue Light Negatively Regulates Tolerance to Phosphate Deficiency in Arabidopsis

Abstract

Plants have evolved mechanisms to improve utilization efficiency or acquisition of inorganic phosphate (Pi) in response to Pi deficiency, such as altering root architecture, secreting acid phosphatases, and activating the expression of genes related to Pi uptake and recycling. Although many genes responsive to Pi starvation have been identified, transcription factors that affect tolerance to Pi deficiency have not been well characterized. We show here that defect in the ELONGATED HYPOCOTYL 5 (HY5) transcription factor gene results in tolerance to Pi deficiency in Arabidopsis. The primary root length of hy5 was only slightly inhibited under Pi deficient condition and its fresh weight was significantly higher than that of wild type. The Pi deficiency-tolerant phenotype of hy5 was similarly observed when grown on the medium without Pi. In addition, a double mutant, hy5slr1, without lateral roots also showed tolerance to phosphate deficiency, indicating that the tolerance of hy5 does not result from increase of external Pi uptake and may be related to internal Pi utilization or recycling. Moreover, we found that blue light negatively regulates tolerance to Pi-deficiency and that hy5 exhibits tolerance to Pi deficiency due to blockage of blue-light responses. Collectively, this study points out light quality may play an important role in the regulation of internal Pi recycling and utilization efficiency. Also, it may contribute to reducing Pi fertilizer requirements in plants through a proper illumination.