A Two-Staged Model of Na+ Exclusion in Rice Explained by 3D Modeling of HKT Transporters and Alternative Splicing

• Published in: PloS one Vol. 7; no. 7; p. e39865
• Main Authors: Cotsaftis, Olivier, Plett, Darren, Shirley, Neil, Tester, Mark, Hrmova, Maria
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 11.07.2012; Public Library of Science (PLoS)
• Subjects: Abiotic stress; Abundance; Accumulation; Alleles; Alternative Splicing; Arabidopsis; Biology; Cation Transport Proteins - chemistry; Cation Transport Proteins - genetics; Cation Transport Proteins - metabolism; Cellulose; Cluster analysis; Complexity; Computer Science; Crystal structure; Crystallography, X-Ray; Gene Expression Regulation, Plant; Genes; Genomes; Genomics; Ion Transport; Leaves; Modelling; Models, Molecular; Oryza - genetics; Oryza - metabolism; Oryza sativa; Photosynthesis; Plant Leaves - genetics; Plant Leaves - metabolism; Plant Proteins - chemistry; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Roots - genetics; Plant Roots - metabolism; Plant Shoots - genetics; Plant Shoots - metabolism; Potassium - metabolism; Protein Conformation; Protein Isoforms - chemistry; Protein Isoforms - genetics; Protein Isoforms - metabolism; Protein structure; Proteins; Quantitative analysis; RNA, Messenger - genetics; RNA, Messenger - metabolism; Salinity; Salinity effects; Salinity tolerance; Salt-Tolerant Plants - genetics; Salt-Tolerant Plants - metabolism; Sodium - metabolism; Symporters - chemistry; Symporters - genetics; Symporters - metabolism; Three dimensional models; Tissues; Transcription; Transpiration; Xylem; Australia; South Australia Australia
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0039865

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.