Expression of the extrinsic 23-kDa protein of photosystem II in response to salt stress is associated with the K+/Na+ discrimination locus Kna1 in wheat

Abstract

A single locus, Kna1, which plays a key role in the control of K+/Na+ discrimination in wheat (Triticum aestivum L.) adapted to salinity, has been mapped within a 1.1-cM region on the 4D/4B map. The investigation presented here examined whether Kna1 modulates specific membrane protein(s). Membrane fractions were isolated from young leaf blades, crowns, and leaf sheaths. Two-dimensional gel electrophoresis was used to search for membrane proteins that may be involved in Kna1 genetic or physiological mechanisms. Protein changes found in the salt-stressed parental Kna1 and kna1 lines were mapped using a population of 4D/4B recombinant lines with variable distal regions of the 4D chromosomes. No protein polymorphisms co-segregated with Kna1 in protein fractions isolated from the crowns, roots, or sheaths. Two up-regulated protein polymorphisms in the leaf blade membrane fraction of salt-stressed plants that completely cosegregated with Kna1 were identified. On the basis of sequence analysis the membrane protein was identical to the extrinsic 23-kDa protein of the oxygen-evolving complex (OEC) of photosystem II. The steady-state mRNA accumulation remained unchanged among different lines under conditions of salt stress. These results suggest that expression of the 23-kDa protein might be modulated by Kna1 at the post-transcriptional level and that the response of protein expression to NaCl stress treatment might attribute to the mechanism of K+/Na+ discrimination in wheat.