Functional characterization of OsMADS18, a member of the AP1/SQUA subfamily of MADS box genes

• Published in: Plant physiology (Bethesda) 2004-08, Vol.135 (4), p.2207-2219
• Main Authors: Fornara, F, Parenicova, L, Falasca, G, Pelucchi, N, Masiero, S, Ciannamea, S, Lopez-Dee, Z, Altamura, M.M, Colombo, L, Kater, M.M
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; amino acid sequences; apetala1 protein; Application programming interfaces; Arabidopsis; Arabidopsis - genetics; Arabidopsis thaliana; Biological and medical sciences; Development and Hormone Action; DNA-binding proteins; Flowering; Flowers; Flowers - genetics; Fundamental and applied biological sciences. Psychology; gene expression regulation; gene overexpression; gene silencing; Genes; Germination; grain crops; MADS box gene; MADS Domain Proteins - chemistry; MADS Domain Proteins - genetics; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; nucleotide sequences; Oryza - genetics; Oryza sativa; Phenotypes; phenotypic variation; plant morphology; plant proteins; Plants; protein-protein interactions; Proteins; Rice; RNA interference; Saccharomyces cerevisiae; Sequence Alignment; Sequence Homology, Amino Acid; squamosa prtoein; transcription factors; Transcription Factors - genetics; Transcription. Transcription factor. Splicing. Rna processing; transgenes; Transgenic plants; two hybrid system techniques; Zea mays - genetics
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.104.045039

MADS box transcription factors controlling flower development have been isolated and studied in a wide variety of organisms. These studies have shown that homologous MADS box genes from different species often have similar functions. OsMADS18 from rice (Oryza sativa) belongs to the phylogenetically defined AP1/SQUA group. The MADS box genes of this group have functions in plant development, like controlling the transition from vegetative to reproductive growth, determination of floral organ identity, and regulation of fruit maturation. In this paper we report the functional analysis of OsMADS18. This rice MADS box gene is widely expressed in rice with its transcripts accumulated to higher levels in meristems. Overexpression of OsMADS18 in rice induced early flowering, and detailed histological analysis revealed that the formation of axillary shoot meristems was accelerated. Silencing of OsMADS18 using an RNA interference approach did not result in any visible phenotypic alteration, indicating that OsMADS18 is probably redundant with other MADS box transcription factors. Surprisingly, overexpression of OsMADS18 in Arabidopsis caused a phenotype closely resembling the ap1 mutant. We show that the ap1 phenotype is not caused by down-regulation of AP1 expression. Yeast two-hybrid experiments showed that some of the natural partners of AP1 interact with OsMADS18, suggesting that the OsMADS18 overexpression phenotype in Arabidopsis is likely to be due to the subtraction of AP1 partners from active transcription complexes. Thus, when compared to AP1, OsMADS18 during evolution seems to have conserved the mechanistic properties of protein-protein interactions, although it cannot complement the AP1 function.