Diversity in the sodium transporter, HKT1;5 within the genus Oryza

The MS Swaminathan Research Foundation's (MSSRF) scientists examined the gene which is a crucial component of making cereal tolerant to salinity. The research paper published in 2021.Salinity is a major abiotic stress affecting rice growth and productivity. It is the most sensitive among all cereals to salinity at seedling and reproductive stages.

A global soil survey was conducted in 1970-80s, which estimated that approximately 6.5 percent of the world's arable and marginal soils were affected by salinity or sodicity (increased sodium ions in the soil). Soil salinity refers to the concentration of salts in the soil solution. It can be due to natural as well as human-induced changes.

Salinity harms crop yield due to the accumulation of sodium in the leaves or shoots that, in turn, affects photosynthesis and grain yield. Rice among cereals is sensitive to salinity at seedling and reproductive stages. In cultivated rice (Oryza sativa), as in other grains, HKT1;5, is a determinant of salinity tolerance.

In rice, HKT1;5 (OsHKT1;5) is expressed in the plasma membrane of specific cells in the root (under salinity) called the xylem parenchyma. When soil salinity increases, sodium ions are taken up by roots and transported to the xylem from where it is transported to shoot tissues. HKT1;5 in the xylem parenchyma functions to 'sequester' sodium ions (into xylem parenchyma cells) from the xylem, preventing sodium from accumulating in the shoots (called ion exclusion).

Variations in OsHKT1;5 sequence are associated with salinity tolerance that alter its sodium transporting properties. 

Asian cultivated rice has two subspecies: indica and japonica. Coastal rice landraces like Pokkali and Nona Bokra (called indica rice) have more efficient sodium transporting versions of OsHKT1;5. In contrast, japonica rice like Koshihikari has less efficient sodium transporting versions of OsHKT1;5. Researchers at the M.S. Swaminathan Research Foundation's (MSSRF) have examined sodium transporter gene (HKT 1;5) diversity in cultivated rice Oryza sativa that is a crucial component of salinity tolerance in rice. A range of intermediate OsHKT1;5 haplotypes or versions have been identified by mining sequencing information for rice deposited in public databases (https://gigascience.biomedcentral.com/articles/10.1186/2047-217X-3-7), the so called ‘3000 rice genome project'.

MSSRF has published this research work in the international journal named Rice Science (Pulipati et al., 2021; http://www.ricescience.org/fileup/PDF/2021-0027W.pdf).

Ms. Shalini Pulipati, a CSIR Senior Research Fellow, from MSSRF has researched along with other research scholars from the foundation. The research article also has contributions from research groups working at The National Centre for Biological Sciences, Bengaluru, National Agri-Food Biotechnology Institute, Mohali and INRAE, National Research Institute for Agriculture, Food and Environment, France.