Molecular and expression analysis of a LIM protein gene family from flowering plants

LIM-domain proteins participate in important cellular processes in eukaryot es, including gene transcription and actin cytoskeleton organization. They are predominantly found in animals, but have also been identified in yeast and plants. Following the characterization of a LIM-domain protein in sunfl ower pollen, we carried out an extensive search for these proteins in flowe ring plants. We have isolated and studied cDNAs and/or genomic sequences fo r two novel LIM-domain proteins from sunflower. three from tobacco, and one from Arabidopsis. The plant proteins are structurally related to the cytos keleton-associated CRP class of LIM proteins in animals, but show several d istinctive features, including a second, atypical, LIM domain. We have perf ormed comparative expression studies of these genes, as well as of one othe r gene from tobacco and two additional Arabidopsis genes whose sequences ar e available from databases. These studies, carried out by RT-PCR in the pre sence of gene-specific primers, showed that, in sunflower and tobacco, poll en grains and sporophytic tissues express different sets of LIM proteins. W ith the exception of one Arabidopsis gene which has two introns - all the g enes analyzed contain four introns at conserved positions, indicating that the ancestral gene from which the various copies evolved in higher plants a lready had this split structure.