A chloroplast-localized serine protease, ATCDPPIV, has altered expression in the Arabidopsis thaliana conditional chlorina 1 mutant

cch1 has near normal levels of chlorophyll ( Chl) at low light conditions, but at moderate light, Chi a and b levels are reduced and the Chi a/b ratio is increased, due to a leaky mutation in the Mg-chelatase enzyme of the Chl biosynthesis pathway. Under the moderate light, Chl starvation condition, light-harvesting complex (Lhcb) proteins disappear from the thylakoid membrane, suggesting the involvement of a protease. Microarray technology was used to discover genes involved in cch1 's acclimation to reduced Chl levels. The microarray compared the expression of approximately 7,500 genes in wildtype (control) and cch1 plants grown under the moderate light condition. Analysis revealed a significant increase in expression of a novel chloroplast-localized gene (AAB63841) we named AtcDPPIV This gene encodes a predicted serine protease, and appears to have an internal start site that allows expression of the protease region of the gene despite a T-DNA insertion into exon three.