Controlling sodium and potassium transport across chloroplast membrane is a key determinant to maintain photosynthesis during salt stress

Bose J1, Jayakannan M1, Malik S1,2, Shabala S3 and Tyerman S1

  1. ARC Centre of Excellence in Plant Energy Biology and School of Agriculture, Food and Wine, University of Adelaide, PMB 1, Glen Osmond SA 5064, Australia.
  2. Federal University of Maranhão, São Luís, MA, Brazil.
  3. School of Land and Food, University of Tasmania, Private Bag 54, Hobart, Tas 7001, Australia.

Salt stress affects photosynthesis by causing ionic imbalance within chloroplasts. A comparison between glycophytes and halophytes revealed that halophytes are superior in regulating sodium and potassium concentration inside chloroplasts during salt stress. However, the molecular identity of ion transport systems involved in sodium and potassium homeostasis in chloroplasts during salt stress are not fully understood. A pyruvate (BASS2- bile acid: sodium symporter2) transporter and a sodium-proton exchanger (NHD1) have been suggested to move sodium in and out of chloroplasts. We studied sodium, potassium and proton transport across isolated chloroplasts of Arabidopsis thaliana BASS2 and NHD1 knockout mutants using ion-selective micro-electrode (MIFE) technique under salt stress. Chloroplasts from the bass2 mutant had reduced sodium entry and potassium loss. The opposite was the case for the ndh1 mutant. The implications of altered sodium and potassium transport in chloroplasts of these mutants on photosynthetic performance and growth under salinity will be presented and discussed.