MIKC type genes of the MADS-box family in wheat: molecular and phylogenetic analysis.

Abstract

The MADS-box family of transcription factors play key roles in the control of development and signal transduction in eukaryotes (1). The MADS family contains a DNA-binding domain (MADS box) and includes two main lineages, type I and type II, both of which are present in plants, animals and fungi (2). Type II MADS-box proteins of plants,also named as MIKCtype proteins, possess three more domains than Type I MADS-box proteins: intervening (I) domain, keratinlike (K) domain and C-terminal (C) domain. In plants MIKC-type genes are involved in several important developmental processes, such as flower morphogenesis, ovule development, vegetative growth, embryogenesis and fruit formation, and through phylogenetic analysis based on sequence comparison, they have been classified into 13 subfamilies (3). The MIKC transcription factors controlling floral organ identity are the best characterized. Analysis of homeotic floral mutants of Arabidopsis resulted in the formulation of the ABCDE genetic model, which explains how the combined functions and organ-specific expression of five gene classes (A, B, C, D and E) specify the identity of the floral organs (sepals, petals, stamens and carpels), forming the four concentric whorls, and ovules (4,5). The most comprehensive cloning and characterization of MIKC genes of grasses have been carried out in maize and rice (6,7). In this study we extend a detailed characterization of the diversity and complexity of MIKC-type genes to hexaploid wheat.