The early light-inducible proteins of barley. Characterization of two families of 2-h-specific nuclear-coded chloroplast proteins.

Within 1-2 h of illumination of etiolated barley plants the mRNAs of seven nuclear-coded proteins are transiently induced. It is proposed that at least some of these proteins are precursors to chloroplast membrane proteins since after posttranslational transport 2-h-specific bands of 18.5 kDa, 18 kDa and 13.5 kDa have been found bound to thylakoid membranes. cDNA clones for these early light-inducible proteins (ELIPs) have been isolated. Hybrid-release translation shows that part of their information must be homologous since the complete set of early light-inducible translation products is obtained with all investigated clones although the proportions of the translated bands vary for individual clones. From hybridization data it is concluded that two ELIP families of high (24-27 kDa) and of low (16-18 kDa) molecular mass exist which are induced in parallel. Induction of ELIPs occurs even at very low light intensities and is saturated at about 1000 lx. Therefore, ELIPs are not considered to represent light stress proteins but to play a regulatory role during development.