Pabuayon Isaiah Catalino M, Jiang Jiafu, Qian Hongjia, Chung Jung-Sung, Shi Huazhong
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79424, USA.
Current address: State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Landscaping, Ministry of Agriculture and Rural Affairs, Key Laboratory of Biology of Ornamental Plants in East China, National Forestry and Grassland Administration, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
Stress Biol. 2021 Nov 22;1(1):14. doi: 10.1007/s44154-021-00014-1.
Soil salinity severely hampers agricultural productivity. Under salt stress, excess Na accumulation causes cellular damage and plant growth retardation, and membrane Na transporters play central roles in Na uptake and exclusion to mitigate these adverse effects. In this study, we performed sos1 suppressor mutant (named sup) screening to uncover potential genetic interactors of SOS1 and additional salt tolerance mechanisms. Map-based cloning and sequencing identified a group of mutants harboring dominant gain-of-function mutations in the vacuolar Na/H antiporter gene AtNHX1. The gain-of-function variants of AtNHX1 showed enhanced transporter activities in yeast cells and increased salt tolerance in Arabidopsis wild type plants. Ion content measurements indicated that at the cellular level, these gain-of-function mutations resulted in increased cellular Na accumulation likely due to enhanced vacuolar Na sequestration. However, the gain-of-function suppressor mutants showed reduced shoot Na but increased root Na accumulation under salt stress, indicating a role of AtNHX1 in limiting Na translocation from root to shoot. We also identified another group of sos1 suppressors with loss-of-function mutations in the Na transporter gene AtHKT1. Loss-of-function mutations in AtHKT1 and gain-of-function mutations in AtNHX1 additively suppressed sos1 salt sensitivity, which indicates that the three transporters, SOS1, AtNHX1 and AtHKT1 function independently but coordinately in controlling Na homeostasis and salt tolerance in Arabidopsis. Our findings provide valuable information about the target amino acids in NHX1 for gene editing to improve salt tolerance in crops.
土壤盐度严重阻碍农业生产力。在盐胁迫下，过量的钠积累会导致细胞损伤和植物生长迟缓，而膜钠转运蛋白在钠的吸收和外排中起核心作用，以减轻这些不利影响。在本研究中，我们进行了sos1抑制突变体（命名为sup）筛选，以发现SOS1的潜在遗传相互作用因子和其他耐盐机制。基于图谱的克隆和测序鉴定出一组在液泡钠/氢反向转运蛋白基因AtNHX1中携带显性功能获得性突变的突变体。AtNHX1的功能获得性变体在酵母细胞中显示出增强的转运活性，并在拟南芥野生型植物中提高了耐盐性。离子含量测量表明，在细胞水平上，这些功能获得性突变可能由于液泡钠隔离增强而导致细胞内钠积累增加。然而，功能获得性抑制突变体在盐胁迫下地上部钠含量降低，但根部钠积累增加，表明AtNHX1在限制钠从根向地上部转运中发挥作用。我们还鉴定出另一组在钠转运蛋白基因AtHKT1中具有功能丧失突变的sos1抑制子。AtHKT1的功能丧失突变和AtNHX1的功能获得性突变可累加抑制sos1的盐敏感性，这表明SOS1、AtNHX1和AtHKT1这三种转运蛋白在控制拟南芥钠稳态和耐盐性方面独立但协同发挥作用。我们的研究结果为通过基因编辑改善作物耐盐性提供了关于NHX1中目标氨基酸的有价值信息。
