Abstract
Rhomboid proteins comprise a class of intramembrane serine proteases, containing six or seven transmembrane helices, conserved in all organisms. Drosophila Rhomboid-1 regulates epidermal growth receptor signaling. The structure and substrate specificities are widely conserved across species. By contrast, the understanding of plant rhomboids is rather limited. In Arabidopsis genome 15 putative rhomboid-like proteins are annotated and 13 or 14 of them are predicted to be catalytically active. AtRBL2 has been predicted to cleave a plastid translocon component Tic40, although the biological meaning of this result is not yet clear. Here, we found that AtRbl10 having chloroplast transit-peptides is involved in ABA response. By screening of 1,290 homozygous T-DNA or transposon insertion-lines grown on agar plate containing ABA, we found that atrbl10 mutants exhibited enhanced ABA-dependent repression of cotyledon expansion and greening. While seedling phenotypes grown under normal conditions did not show any differences between the wild-type and atrbl10 mutant plants. Expression analyses using GFP or GUS fusion proteins are currently undertaken. The detail will be presented.
