Molecular characterization of organellar rhomboid proteins inArabidopsis

Abstract

The list of cellular processes involving rhomboid serine proteases and regulated intramembrane proteolysis (RIP) is growing, diverse, and spans different species. The latest entrants to the RIP phenomenon are the plant rhomboid proteases. Although natural rhomboid protease substrates and their corresponding processes have been identified from insects to mammals, the current knowledge on plant rhomboid proteases is limited. This study was thus aimed at revealing further details about the roles of three Arabidopsis organellar rhomboid proteases and like proteins. Globally, the patterns revealed at the transcript level suggest that the three Arabidopsis rhomboid proteins under study are linked partly to growth and development. Further evidence for a linkage to growth and development was obtained for the organellar rhomboid protein, At1g74130. This link was most evident during the early growth phases of the various tissues assessed, e.g., At1g74130 expression was greater in young, expanding leaves than in mature leaves. This expression pattern appears to correlate with the responses of the Arabidopsis At1g74130 mutant, where there were observable delays in germination and growth. These delays appear to be associated with the early stages of plastid development and can be observed as changes at the cellular level and at the level of chlorophyll content. The data reported here suggest that organellar rhomboid proteins, in particular At1g74130, may take part in growth and development.