title: A comparative gene analysis with rice identified orthologous group II HKT genes and their association with Na(+) concentration in bread wheat.
abstract: BACKGROUND
  Although the HKT transporter genes ascertain some of the key determinants of crop salt tolerance mechanisms, the diversity and functional role of group II HKT genes are not clearly understood in bread wheat. The advanced knowledge on rice HKT and whole genome sequence was, therefore, used in comparative gene analysis to identify orthologous wheat group II HKT genes and their role in trait variation under different saline environments.
  
  
  RESULTS
  The four group II HKTs in rice identified two orthologous gene families from bread wheat, including the known TaHKT2;1 gene family and a new distinctly different gene family designated as TaHKT2;2. A single copy of TaHKT2;2 was found on each homeologous chromosome arm 7AL, 7BL and 7DL and each gene was expressed in leaf blade, sheath and root tissues under non-stressed and at 200 mM salt stressed conditions. The proteins encoded by genes of the TaHKT2;2 family revealed more than 93% amino acid sequence identity but ≤52% amino acid identity compared to the proteins encoded by TaHKT2;1 family. Specifically, variations in known critical domains predicted functional differences between the two protein families. Similar to orthologous rice genes on chromosome 6L, TaHKT2;1 and TaHKT2;2 genes were located approximately 3 kb apart on wheat chromosomes 7AL, 7BL and 7DL, forming a static syntenic block in the two species. The chromosomal region on 7AL containing TaHKT2;1 7AL-1 co-located with QTL for shoot Na(+) concentration and yield in some saline environments.
  
  
  CONCLUSIONS
  The differences in copy number, genes sequences and encoded proteins between TaHKT2;2 homeologous genes and other group II HKT gene families within and across species likely reflect functional diversity for ion selectivity and transport in plants. Evidence indicated that neither TaHKT2;2 nor TaHKT2;1 were associated with primary root Na(+) uptake but TaHKT2;1 may be associated with trait variation for Na(+) exclusion and yield in some but not all saline environments.
authors.affiliation: School of Plant Biology and Institute of Agriculture, The University of Western Australia, Crawley, 6009, Western Australia. 20881006@student.uwa.edu.au.|State Agricultural Biotechnology Centre, Murdoch University, Murdoch, 6150, Western Australia. 20881006@student.uwa.edu.au.
authors.forename: H A Chandima K
authors.initials: HA
authors.lastname: Ariyarathna
authors.affiliation: South Australia Research Development Institute, Plant Genomics Centre, Waite Research Precinct, Urrbrae, 5064, South Australia. klaus.oldach@kws.com.
authors.forename: Klaus H
authors.initials: KH
authors.lastname: Oldach
authors.affiliation: State Agricultural Biotechnology Centre, Murdoch University, Murdoch, 6150, Western Australia. michael.francki@agric.wa.gov.au.|Department of Agriculture and Food Western Australia, South Perth, 6151, Western Australia. michael.francki@agric.wa.gov.au.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Francki
mesh_terms: D001939:Bread; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D017343:Genes, Plant; D018745:Genome, Plant; D005810:Multigene Family; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics; D027961:Potassium-Hydrogen Antiporters / Q000235:genetics*; D017422:Sequence Analysis, DNA; D012964:Sodium / Q000378:metabolism; D014908:Triticum / Q000235:genetics* / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D027961:Potassium-Hydrogen Antiporters; D012964:Sodium