Phosphate deficiency signaling pathway is a target of arsenate and phosphate transporter OsPT1 is involved in As accumulation in shoots of rice

Abstract

Arsenate [As(V)] is toxic to organisms, and phosphate (Pi) transporter can mediate As(V) uptake due to their similarity in chemical structure. In the rice (Oriza sativa L.) genome, 13 Pi transporter genes (OsPTs) are present. Their response to As(V) and contribution to As(V) accumulation are unknown. We determined absolute mRNA amount of OsPTs in rice seedlings and OsPT1, OsPT2, OsPT4, and OsPT8 were quantified by real-time polymerase chain reaction (PCR). OsPT2, OsPT4, and OsPT8 were highly induced by Pi deficiency, while OsPT1 was not. In accordance with Pi deficiency response, OsPT2, OsPT4, and OsPT8 induction by Pi deficiency were severely suppressed by As(V). Those data suggest that As(V) affects Pi deficiency signaling in rice. To examine the As(V) transport activity of OsPT1 in planta, we obtained T-DNA mutant of OsPT1 (ospt1). The transcript expression level of OsPT1 in ospt1 was reduced by 70% in shoots and 50% in roots compared to those in the wild-type (WT), and arsenic (As) concentrations in shoots were reduced by 60% compared to WT. We further overexpressed OsPT1-GFP in rice. Overexpression lines showed higher As accumulation in shoots compared to wild-type. OsPT1-GFP is localized to plasma membrane. These results indicate that OsPT1 is involved in As(V) uptake from soil or apoplast.