A two-staged model of Na+ exclusion in rice explained by 3D modeling of HKT transporters and alternative splicing.
The HKT family of Na(+) and Na(+)/K(+) transporters is implicated in plant salinity tolerance. Amongst these transporters, the cereal HKT1;4 and HKT1;5 are responsible for Na(+) exclusion from photosynthetic tissues, a key mechanism for plant salinity tolerance. It has been suggested that Na(+) is retrieved from the xylem transpiration stream either in the root or the leaf sheath, protecting the leaf blades from excessive Na(+) accumulation. However, direct evidence for this scenario is scarce. Comparative modeling and evaluation of rice (Oryza sativa) HKT-transporters based on the recent crystal structure of the bacterial TrkH K(+) transporter allowed to reconcile transcriptomic and physiological data. For OsHKT1;5, both transcript abundance and protein structural features within the selectivity filter could control shoot Na(+) accumulation in a range of rice varieties. For OsHKT1;4, alternative splicing of transcript and the anatomical complexity of the sheath needed to be taken into account. Thus, Na(+) accumulation in a specific leaf blade seems to be regulated by abundance of a correctly spliced OsHKT1;4 transcript in a corresponding sheath. Overall, allelic variation of leaf blade Na(+) accumulation can be explained by a complex interplay of gene transcription, alternative splicing and protein structure.
Australian Centre for Plant Functional Genomics, University of Adelaide, Adelaide, South Australia, Australia. oliv.cotsaftis@gmail.com
Olivier
O
Cotsaftis
Darren
D
Plett
Neil
N
Shirley
Mark
M
Tester
Maria
M
Hrmova
D000483:Alleles; D017398:Alternative Splicing; D027682:Cation Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018360:Crystallography, X-Ray; D018506:Gene Expression Regulation, Plant; D017136:Ion Transport; D008958:Models, Molecular; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D054712:Salinity; D055051:Salt-Tolerant Plants / Q000235:genetics* / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D027981:Symporters / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D027682:Cation Transport Proteins; C088864:HKT1 protein, plant; D010940:Plant Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D027981:Symporters; D012964:Sodium; D011188:Potassium