Location: Plant, Soil and Nutrition ResearchTitle: Phosphate transporters OsPHT1;9 and OsPHT1;10 are involved in phosphate uptake in rice) Author
Submitted to: Plant Cell and Environment
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2014
Publication Date: 5/1/2014
Citation: Wang, X., Wang, Z., Pineros, M., Wang, Z., Wang, W., Li, C., Wu, Z., Kochian, L.V., Wu, P. 2014. Phosphate transporters OsPHT1;9 and OsPHT1;10 are involved in phosphate uptake in rice. Plant Cell and Environment. 37(5):1159-1170. DOI: 10.1111/pce.201437.issue-5/issuetoc. Interpretive Summary: Phosphorus (P) is one of the most limiting mineral nutrients for plant growth. It is an essential macronutrient and P fertilizer reserves are a resource that is becoming more scarce worldwide. Also P which predominantly exists as the phosphate anion (Pi) in the soil diffuses slowly in the soil solution and often is fixed on the surface of soil particles, making it relatively unavailable to the plant root. Hence plants have evolved a number of adaptive strategies to acquire this relatively unavailable mineral nutrient from the soil. One of these strategies involves the existence of a large number of different Pi transporters that are localized throughout the plant and mediate the uptake, transport and accumulation of Pi in the plant. In this study we cloned two rice Pi transporter genes, named OsPT9 and OsPT10, and characterized their gene expression in response to low Pi status, their localization in different plant tissues, and their function by expressing them in two different single cell systems (frog eggs and yeast) to study their Pi transport properties. We also overexpressed and knocked out the expression of the OsPT9 and 10 genes in transgenic rice plants to better understand their function in planta. We found that both transporters are expressed in the root epidermis of mature roots and in the leaf, especially around the leaf veins. Transport characterization showed that both transporters absorb Pi at low external concentrations, demonstrating they are both high affinity Pi uptake transporters. Our findings indicate that these two transporters function redundantly to both mediate Pi uptake from the soil and also absorb Pi into leaf cells after it is translocated from the root to the shoot.
Technical Abstract: We characterized the function of two rice phosphate (Pi) transporters: OsPHT1;9 (OsPT9) and OsPHT1;10 (OsPT10). OsPT9 and OsPT10 were expressed in the root epidermis, root hairs, and lateral roots, with the expression being specifically induced by Pi-starvation. In leaves, the expression of the two genes was observed in both mesophyll and vasculature. High-affinity Km values for Pi transport of OsPT9 and OsPT10 were determined by yeast experiments and two-electrode voltage clamp analysis of anion transport in Xenopus oocytes expressing OsPT9 and OsPT10. Pi uptake and Pi concentrations in the transgenic plants harbouring overexpressed OsPT9 and OsPT10 were determined by Pi concentration analysis and P-labelled Pi-uptake rate analysis. Significantly higher Pi-uptake rates in the transgenic plants compared to the wild-type plants were observed under both high-Pi and low-Pi solution culture conditions. Conversely, although no alterations in Pi concentration were found in OsPT9 or OsPT10 knockdown plants, a significant reduction in Pi concentration in both shoots and roots was observed in double-knockdown plants grown under both high- and low-Pi conditions. Taken together, our results suggest that OsPT9 and OsPT10 redundantly function in Pi uptake.