LEUNIG, a putative transcriptional corepressor that regulates AGAMOUS expression during flower development

Regulation of homeotic gene expression is critical for proper developmental patterns in both animals and plants. LEUNIG is a key regulator of the Arabidopsis floral homeotic gene AGAMOUS. Mutations in LEUNIG cause ectopic AGAMOUS mRNA expression in the outer two whorls of a flower, leading to homeotic transformations of floral organ identity as well as loss of floral organs. We isolated the LEUNIG gene by using a map-based approach and showed that LEUNIG encodes a glutamine-rich protein with seven WD repeats and is similar in motif structure to a class of functionally related transcriptional corepressors including Tup1 from yeast and Groucho from Drosophila. The nuclear localization of LEUNIG-GFP is consistent with a role of LEUNIG as a transcriptional regulator. The detection of LEUNIG mRNA in all floral whorls at the time of their inception suggests that the restricted activity of LEUNIG in the outer two floral whorls must depend on interactions with other spatially restricted factors or on posttranslational regulation. Our finding suggests that both animals and plants use similar repressor proteins to regulate critical developmental processes.