Allelic variants of OsHKT1;1 underlie the divergence between indica and japonica subspecies of rice (Oryza sativa) for root sodium content

Authors

Malachy T. Campbell, University of Nebraska-LincolnFollow
Nonoy Bandillo, University of Nebraska-LincolnFollow
Fouad Razzaq A. Al Shiblawi, Universite Montpellier
Sandeep Sharma, University of Nebraska-Lincoln
Kan Liu, University of Nebraska-Lincoln
Qian Du, University of Nebraska-Lincoln
Aaron J. Schmitz, University of Nebraska-Lincoln
Chi Zhang, University of Nebraska-LincolnFollow
Anne-Alienor Very, Universite Montepellier
Aaron J. Lorenz, University of Nebraska-LincolnFollow
Harkamal Walia, University of Nebraska-LincolnFollow

ORCID IDs

Harkamal Walia

Date of this Version

2017

Citation

Campbell MT, Bandillo N, Al Shiblawi FRA, Sharma S, Liu K, Du Q, et al. (2017) Allelic variants of OsHKT1;1 underlie the divergence between indica and japonica subspecies of rice (Oryza sativa) for root sodium content. PLoS Genet 13(6): e1006823. https://doi.org/10.1371/journal. pgen.1006823

Comments

Copyright © 2017 Campbell et al. This is an open access article distributed under the terms of the Creative Commons Attribution License.

Abstract

Salinity is a major factor limiting crop productivity. Rice (Oryza sativa), a staple crop for the majority of the world, is highly sensitive to salinity stress. To discover novel sources of genetic variation for salt tolerance-related traits in rice, we screened 390 diverse accessions under 14 days of moderate (9 dS m^-1) salinity. In this study, shoot growth responses to moderate levels of salinity were independent of tissue Na⁺ content. A significant difference in root Na+ content was observed between the major subpopulations of rice, with indica accessions displaying higher root Na⁺ and japonica accessions exhibiting lower root Na+ content. The genetic basis of the observed variation in phenotypes was elucidated through genomewide association (GWA). The strongest associations were identified for root Na⁺:K⁺ ratio and root Na⁺ content in a region spanning ~575 Kb on chromosome 4, named Root Na⁺ Content 4 (RNC4). Two Na⁺ transporters, HKT1;1 and HKT1;4 were identified as candidates for RNC4. Reduced expression of both HKT1;1 and HKT1;4 through RNA interference indicated that HKT1;1 regulates shoot and root Na⁺ content, and is likely the causal gene underlying RNC4. Three non-synonymous mutations within HKT1;1 were present at higher frequency in the indica subpopulation. When expressed in Xenopus oocytes the indica-predominant isoform exhibited higher inward (negative) currents and a less negative voltage threshold of inward rectifying current activation compared to the japonica-predominant isoform. The introduction of a 4.5kb fragment containing the HKT1;1 promoter and CDS from an indica variety into a japonica background, resulted in a phenotype similar to the indica subpopulation, with higher root Na⁺ and Na⁺:K⁺. This study provides evidence that HKT1;1 regulates root Na⁺ content, and underlies the divergence in root Na⁺ content between the two major subspecies in rice.