Original Research ARTICLE
Tissue-specific regulation of Na+ and K+ transporters explains genotypic differences in salinity stress tolerance in rice
- 1Henan Agricultural University, China
- 2School of Agricultural Science, University of Tasmania, Australia
- 3University of Tasmania, Australia
- 4M S Swaminathan Research Foundation, India
- 5Western Sydney University, Australia
- 6Zhejiang University, China
Rice (Oryza sativa) is a staple food that feeds more than half the world population. As rice is highly sensitive to soil salinity, current trends in soil salinization threaten global food security. To better understand the mechanistic basis of salinity tolerance in rice, three contrasting rice cultivars – Reiziq (tolerant), Doongara (moderately tolerant), and Koshihikari (sensitive) were examined and the differences in operation of key ion transporters mediating ionic homeostasis in these genotypes evaluated. Tolerant varieties had reduced Na+ translocation from roots to shoots. Electrophysiological and qRT-PCR experiments showed that tolerant genotypes possessed 2-fold higher net Na+ efﬂux capacity in the root elongation zone. Interestingly, this efflux was only partially mediated by the plasma membrane (PM) Na+/H+ antiporter (OsSOS1), suggesting involvement of some other exclusion mechanisms. No significant difference in Na+ exclusion from the mature root zones was found between cultivars, and the transcriptional changes in the SOS signalling pathway genes in the elongation zone were not correlated with the genetic variability in salinity tolerance amongst genotypes. The most important hallmark of differential salinity tolerance was in the ability of the plant to retain K+ in both root zones. This trait was conferred by at least three complementary mechanisms: (1) its superior ability to activate H+-ATPase pump operation, both at transcriptional and functional levels; (2) reduced sensitivity of K+ efflux channels to reactive oxygen species (ROS); and (3) smaller upregulation in OsGORK and higher upregulation of OsAKT1 in tolerant cultivars in response to salt stress. These traits should be targeted in breeding programs aimed to improve salinity tolerance in commercial rice cultivars.
Keywords: root, H+ATPase, Sodium, Potassium, Na/H Exchanger, Reactive Oxygen Species
Received: 24 Jul 2019;
Accepted: 03 Oct 2019.
Copyright: © 2019 Liu, Shabala, Shabala, Zhou, Meinke, Venkataraman, Chen, Zeng and Zhao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Prof. Sergey Shabala, University of Tasmania, School of Agricultural Science, Hobart, 7001, Tas, Australia, Sergey.Shabala@utas.edu.au