Na+ transporter HKT1;2 reduces flower Na+ content and considerably mitigates the decline in tomato fruit yields under saline conditions

[EN] Genes encoding HKT1-like Na+ transporters play a key role in the salinity tolerance mechanism in Arabidopsis and other plant species by retrieving Na+ from the xylem of different organs and tissues. In this study, we investigated the role of two HKT1;2 allelic variants in tomato salt tolerance in relation to vegetative growth and fruit yield in plants subjected to salt treatment in a commercial greenhouse under real production conditions. We used two near-isogenic lines (NILs), homozygous for either the Solanum lycopersicum (NIL17) or S. cheesmaniae (NIL14) allele, at HKT1;2 loci and their respective RNAi-Sl/ScHKT1;2 lines. The results obtained show that both ScHKT1;2- and SIHKTI;2-silenced lines display hypersensitivity to salinity associated with an altered leaf Na+/K+ ratio, thus confirming that HKT1;2 plays an important role in Na+ homeostasis and salinity tolerance in tomato. Both silenced lines also showed Na+ over-accumulation and a slight, but significant, reduction in K+ content in the flower tissues of salt-treated plants and consequently a higher Na+/K+ ratio as compared to the respective unsilenced lines. This altered Na+/K+ ratio in flower tissues is associated with a sharp reduction in fruit yield, measured as total fresh weight and number of fruits, in both silenced lines under salinity conditions. Our findings demonstrate that Na+ transporter HKT1;2 protects the flower against Na+ toxicity and mitigates the reduction in tomato fruit yield under salinity conditionsWe wish to thank Emilio Jaime Fernandez (La Mayora, IHMS-CSIC) and Elena Sanchez Romero (EEZ-CSIC) for their technical assistance, the Scientific Instrumentation Service at EEZ-CSIC for their ICP-OES mineral analysis and Michael O'Shea for proofreading the text. The study was funded by EU-cofinanced grants from Agencia Estatal de Investigacion, Spanish Ministry of Economy, Industry and Competition (AGL2013-41733-R and AGL2017-82452-C2-1R to A.B., AGL2017-82452-C2-2R to M.J.A.) and the University of Granada (ACCESP2018-4 to JAT).Romero-Aranda, MR.; Gonzalez-Fernandez, P.; Pérez-Tienda, JR.; López-Díaz, MR.; Espinosa, J.; Granum, E.; Traverso, JÁ.... (2020). Na+ transporter HKT1;2 reduces flower Na+ content and considerably mitigates the decline in tomato fruit yields under saline conditions. Plant Physiology and Biochemistry. 154:341-352. https://doi.org/10.1016/j.plaphy.2020.05.012S34135215