Sodium Transporter HKT1;5 Diversity in Genus Oryza

TitleSodium Transporter HKT1;5 Diversity in Genus Oryza
Publication TypeJournal Article
Year of Publication2021
AuthorsPulipati S, Somasundaram S., Rana N, Kumaresan K, Shafi M, Civan P, Sellamuthu G, Jaganathan D, Ramaravi PVenkatesan, Punitha S., Raju K, Mantri SS, Sowdhamini R., Ajay P, Venkataraman G
Date Published2021
Type of ArticleJournal
Keywordsbacterial artificial chromosome, Haplotype, HKT1;5 diversity, salinity tolerance, single nucleotide polymorphism

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. HKR1;5 sequences from more recently evolved Oryza species (O. sativalO. officinalis complex species) contain two expansions that involve two intracellularly oriented loops/helical regions between MPM domains, pptentially governing transport characteristics, while more ancestral HKT1;5 sequences have shorter intracellular loops. We compared homology models for homoeologous OcHKT1;5-K and OcHKT1;5L 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 rece species (O.nivara and O.rufipogon). Progenitor HKT1;5 haplotypes can thus be used as novel p[otential donors for enhancing cultivated rice salinity tolerance. Within Asian rice accessions, 10occur in mutually exclusive japonica and indica groups, corresponding to haplotypes seen 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 3000 rice dataset may relate to eco-physiological fitness in specific geo-climatic and/or edaphic contexts.

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