Two closely linked tomato HKT coding genes are positional candidates for the major tomato QTL involved in Na+/K+ homeostasis

• Published in: Plant, cell and environment cell and environment, 2013-06, Vol.36 (6), p.1171-1191
• Main Authors: ASINS, MARIA JOSÉ, VILLALTA, IRENE, ALY, MOHAMED M., OLÍAS, RAQUEL, ÁLVAREZ DE MORALES, PAZ, HUERTAS, RAÚL, LI, JUN, JAIME‐PÉREZ, NOELIA, HARO, ROSARIO, RAGA, VERÓNICA, CARBONELL, EMILIO A., BELVER, ANDRÉS
• Format: Article
• Language: English
• Subjects: Alleles; Amino Acid Sequence; Base Sequence; Biological and medical sciences; candidate gene analysis; Cation Transport Proteins - genetics; Cation Transport Proteins - metabolism; Chromosomes, Plant; Fundamental and applied biological sciences. Psychology; Genetic Complementation Test; HKT1‐like genes; Homeostasis; Homeostasis - genetics; K+ and Na+ concentration; Lycopersicon esculentum; Lycopersicon esculentum - genetics; Lycopersicon esculentum - metabolism; Molecular Sequence Data; Plant Proteins - genetics; Plant Proteins - metabolism; Potassium - physiology; Quantitative Trait Loci; Sequence Analysis, DNA; Sodium - physiology; Solanum cheesmaniae; Solanum lycopersicum; Symporters - genetics; Symporters - metabolism
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.12051

Control of intracellular Na+ and K+ concentrations in plant tissues under saline conditions is crucial for salt tolerance. In this study, two Na+‐selective class I‐HKT transporters, HKT1;1 and HKT1;2, from tomato were found to be closely linked in proximity to the position with the maximum LOD score for major QTLs in chromosome 7 (at a distance of 35 kb), thus contributing to stem and leaf Na+ and K+ in two populations of tomato RILs derived from two salt‐tolerant lines from wild tomato species S. pimpinellifolium and S. cheesmaniae. This result, together with their patterns of expression and phenotypic effects on a pair of near isogenic lines (NILs) differing in terms of HKT1‐like alleles, support the hypothesis that HKT1;1 and/or HKT1;2 genes underlies a major tomato QTL for shoot Na+/K+. The location of major quantitative trait loci (QTL) contributing to stem and leaf [Na+] and [K+] was previously reported in chromosome 7 using two connected populations of recombinant inbred lines (RILs) of tomato. HKT1;1 and HKT1;2, two tomato Na+‐selective class I‐HKT transporters, were found to be closely linked, where the maximum logarithm of odds (LOD) score for these QTLs located. When a chromosome 7 linkage map based on 278 single‐nucleotide polymorphisms (SNPs) was used, the maximum LOD score position was only 35 kb from HKT1;1 and HKT1;2. Their expression patterns and phenotypic effects were further investigated in two near‐isogenic lines (NILs): 157‐14 (double homozygote for the cheesmaniae alleles) and 157‐17 (double homozygote for the lycopersicum alleles). The expression pattern for the HKT1;1 and HKT1;2 alleles was complex, possibly because of differences in their promoter sequences. High salinity had very little effect on root dry and fresh weight and consequently on the plant dry weight of NIL 157‐14 in comparison with 157‐17. A significant difference between NILs was also found for [K+] and the [Na+]/[K+] ratio in leaf and stem but not for [Na+] arising a disagreement with the corresponding RIL population. Their association with leaf [Na+] and salt tolerance in tomato is also discussed.