
@article {105475,
	title = {Diversity of Sodium Transporter HKT1;5 in Genus Oryza},
	journal = {RICE SCIENCE},
	volume = {29},
	year = {2022},
	month = {01/2022},
	pages = {31-46},
	abstract = {<p>Asian cultivated rice shows allelic variation in sodium transporter, OsHKT1;5, correlating with shoot sodium exclusion (salinity tolerance). These changes map to intra/extracellularly-oriented loops that occur between four transmembrane-P loop-transmembrane (MPM) motifs in OsHKT1;5. HKT1;5 sequences from more recently evolved Oryza species (O. sativa/O. officinalis complex species) contain two expansions that involve two intracellularly oriented loops/helical regions between MPM domains, potentially governing transport characteristics, while more ancestral HKT1;5 sequences have shorter intracellular loops. We compared homology models for homoeologous OcHKT1;5-K and OcHKT1;5-L from halophytic O. coarctata to identify complementary amino acid residues in OcHKT1;5-L that potentially enhance affinity for Na+. Using haplotyping, we showed that Asian cultivated rice accessions only have a fraction of HKT1;5 diversity available in progenitor wild rice species (O. nivara and O. rufipogon). Progenitor HKT1;5 haplotypes can thus be used as novel potential donors for enhancing cultivated rice salinity tolerance. Within Asian rice accessions, 10 non-synonymous HKT1;5 haplotypic groups occur. More HKT1;5 haplotypic diversities occur in cultivated indica gene pool compared to japonica. Predominant Haplotypes 2 and 10 occur in mutually exclusive japonica and indica groups, corresponding to haplotypes in O. sativa salt-sensitive and salt-tolerant landraces, respectively. This distinct haplotype partitioning may have originated in separate ancestral gene pools of indica and japonica, or from different haplotypes selected during domestication. Predominance of specific HKT1;5 haplotypes within the 3 000 rice dataset may relate to eco-physiological fitness in specific geo-climatic and/or edaphic contexts.</p>
},
	doi = {10.1016/j.rsci.2021.12.003},
	author = {Pulipati, Shalini and Somasundaram, Suji and Rana, Nitika and Kumaresan, Kavitha and Shafi, Mohamed and Civan, Peter and Sellamuthu, Gothandapani and Jaganathan, Deepa and Ramaravi, Prasanna Venkatesan and Punitha, S. and Raju, Kalaimani and Mantri, Shrikant S. and Sowdhamini, R. and Parida, Ajay and Venkataraman, Gayatri}
}
@article {78101,
	title = {Homology modeling identifies crucial amino-acid residues that confer higher Na+ transport capacity of OcHKT1;5 from Oryza coarctata Roxb.},
	journal = {Plant Cell Physiol},
	year = {2020},
	month = {2020 May 07},
	abstract = {<p>HKT1;5 loci/alleles are important determinants of crop salinity tolerance. HKT1;5s encode plasmalemma-localized Na+-transporters, retrieving xylem Na+ into xylem parenchyma cells, reducing shoot Na+ accumulation. Allelic variation in rice OsHKT1;5 sequence in specific landraces (Nona Bokra OsHKT1;5-NB/Nipponbare OsHKT1;5-Ni) correlates with variation in salt tolerance. Oryza coarctata, a halophytic wild rice, grows in fluctuating salinity at the seawater-estuarine interface in Indian and Bangladeshi coastal regions. The distinct transport characteristics of the shoots and roots expressing O. coarctata OcHKT1;5 transporter, are reported vis-{\`a}-vis OsHKT1;5-Ni. Yeast sodium extrusion-deficient cells expressing\&nbsp;OcHKT1;5 are sensitive to increasing Na+ (10-100 mM). Electrophysiological measurements in Xenopus oocytes expressing O. coarctata or rice HKT1;5 transporters indicates that OcHKT1;5, like OsHKT1;5-Ni is a Na+-selective transporter, but displays 16-fold lower affinity for Na+ and 3.5-fold higher maximal conductance than OsHKT1;5-Ni. For Na+ concentrations greater than 10 mM, OcHKT1;5 conductance is higher than that of OsHKT1;5-Ni, indicating potential of OcHKT1;5 for increasing domesticated rice salt tolerance. Homology modeling/ simulation suggests that four key amino acid changes in OcHKT1;5 (in loops on the extracellular side; E239K, G207R, G214R, L363V), account for its lower affinity and higher Na+ conductance vis-{\`a}-vis OsHKT1;5-Ni. Of these, E239K in OcHKT1;5, confers lower affinity for Na+ transport, as evidenced by Na+ transport assays of reciprocal site directed mutants for both transporters (OcHKT1;5- K239E, OsHKT1;5-Ni- E270K) in Xenopus oocytes. Both transporters have analogous roles in xylem sap desalinization and differences in Na+ transport affinity/ conductance between the transporters is attributable to differences in xylem sap Na+ concentrations in both species.</p>
},
	issn = {1471-9053},
	doi = {10.1093/pcp/pcaa061},
	author = {Somasundaram, Suji and V{\'e}ry, Anne-Ali{\'e}nor and Vinekar, Rithvik S and Ishikawa, Tetsuya and Kumari, Kumkum and Pulipati, Shalini and Kumaresan, Kavitha and Corratg{\'e}-Faillie, Claire and Sowdhamini, R and Parida, Ajay and Shabala, Lana and Shabala, Sergey and Venkataraman, Gayatri}
}
