Genomic organization and expression profile of a gene encoding makorin RING zinc finger protein in germinating pea (Pisum sativum L. var. Alaska) seeds

The makorin RING finger protein gene (MKRN) family encodes proteins with a characteristic array of zinc-finger motifs. In the present study, we characterized the structure and expression of MKRN gene from pea ( Pisum sativum L. Var-Alaska). Pea MKRN cDNA encoded a putative protein, makorin, with four C3H zinc-finger-motifs, one Cys-His putative zinc-finger motif, and one RING zinc-finger motif. The presence of this distinct motif organization clearly established this gene in pea as a true MKRN ortholog. We also isolated RNA from embryonic axes of seeds at various stages of imbibition and germination, including dry seeds, and studied the temporal expression profile of MKRN by RT-PCR. This analysis revealed that MKRN transcripts were present at very low levels, even in dry seeds. The expression of MKRN increased slowly in imbibition period, leveled off in the germination period, and declined in the seedling growth stage. Our reference genes, cytoskeletal actin ( ACT) and tubulin (TUB1), were expressed from the early stages of imbibition and steadily increased during germination and plateaued 16-35 h after germination. Similar to MKRN transcripts, TUB1 and ACT transcripts were also detected in dry embryo cDNA. After 62 h of germination, a tissue-dependent expression pattern of MKRN was observed highest in root, moderate in stem, and lowest in plumule. The presence of MKRN transcripts in dry seed and the very early induction of MKRN in germination suggest a developmental role for makorin in pea.