Effect of phytochrome-mediated red light signaling on phosphorus uptake and accumulation in rice

Abstract

ABSTRACT Phosphorus (P) is a macronutrient essential for plant growth and productivity. Plants uptake P as inorganic phosphate (Pi); however, in the natural ecosystem, Pi availability is frequently a severe limiting factor for plant growth. Thus, plants have evolved several mechanisms, such as the expression of Pi starvation-responsive genes, to adapt to Pi deficient conditions. Although we recently reported that phytochrome (Phy)-mediated red light signaling promotes Pi uptake by increasing expression levels of such genes in the model plant Arabidopsis, it remains elusive whether a similar mechanism exists in agricultural crops. In the present study, we analyzed the effects of red light signaling on Pi uptake in rice (Oryza sativa L.) using osphyA and osphyB single mutants, and the osphyA osphyB double mutant. Unlike osphyA seedlings, osphyB seedlings showed a reduction in Pi uptake and Pi content. Furthermore, illumination of wild-type seedlings with red light significantly promoted Pi uptake, whereas illumination with blue or far-red light did not. The osphyB mutant showed reduced expression levels of several Pi starvation-responsive genes including Pi transporter genes. Additionally, these phenotypes of osphyB knockout mutants were much more evident under Pi deficient conditions than under Pi sufficient conditions. Moreover, red light promoted Pi uptake in seedlings of other plant species including broccoli (Brassica oleracea L. var. italica) and lettuce (Latuca sativa L.). These results suggest that OsPhyB-mediated red light signaling promotes Pi uptake in rice by up-regulating the expression of Pi starvation response-associated genes, and this phenomenon may be conserved in a wide range of plant species.