Novel resistance mechanism of barley chlorina f104 antenna mutant against photoinhibition: possible role of new identified chloroplastic cpNrp protein

Abstract

Protein with NmrA domain serving as the receptor for oxidized NAD(+)/NADP was identified in chloroplasts of spring barley mutant chlorina f104. NmrA was upregulated under environmental stresses in comparison to wild type plants. Following bioinformatic analysis revealed the nuclear localization signal in this protein. Pathways for the protein transport from cytoplasm into the chloroplast are described, but the mechanism of protein transport from chloroplast to nucleus, where the gene transcription can be possibly affected, is not clear. This protein named as cpNrp (chloroplastic NmrA related protein) is probably a member of new protein family and can serve as chloroplastic redox receptor. Consequently, cpNrp transported as a signal molecule into the nucleus and influences on the gene transcription under environmental stresses (high light radiation). It can be suggested that the presence of these proteins in chloroplasts of chlorina f104 barley mutant is related to up-regulation of photoprotective mechanisms, contributing to maintenance of high resistance against photooxidative damage in conditions of excessive light intensity.