Novel members of the AGAMOUS LIKE 6 subfamily of MIKCC-type MADS-box genes in soybean

Chui E Wong,Prem L Bhalla,Mohan B Singh

doi:10.1186/1471-2229-13-105

Abstract

BackgroundThe classical (C) MIKC-type MADS-box transcription factors comprise one gene family that plays diverse roles in the flowering process ranging from floral initiation to the development of floral organs. Despite their importance in regulating developmental processes that impact crop yield, they remain largely unexplored in the major legume oilseed crop, soybean.ResultsWe identified 57 MIKCc-type transcription factors from soybean and determined the in silico gene expression profiles of the soybean MIKCc-type genes across different tissues. Our study implicates three MIKCc-type transcription factors as novel members of the AGAMOUS LIKE 6 (AGL6) subfamily of the MIKCC-type MADS-box genes, and we named this sister clade PsMADS3. While similar genes were identified in other legume species, poplar and grape, no such gene is represented in Arabidopsis thaliana or rice. RT-PCR analysis on these three soybean PsMADS3 genes during early floral initiation processes revealed their temporal expression similar to that of APETALA1, a gene known to function as a floral meristem identity gene. However, RNA in situ hybridisation showed that their spatial expression patterns are markedly different from those of APETALA1.ConclusionLegume flower development system differs from that in the model plant, Arabidopsis. There is an overlap in the initiation of different floral whorls in soybean, and inflorescent meristems can revert to leaf production depending on the environmental conditions. MIKCC-type MADS-box genes have been shown to play key regulatory roles in different stages of flower development. We identified members of the PsMADS3 sub-clade in legumes that show differential spatial expression during floral initiation, indicating their potential novel roles in the floral initiation process. The results from this study will contribute to a better understanding of legume-specific floral developmental processes.

Highlights

The classical (C) MIKC-type MADS-box transcription factors comprise one gene family that plays diverse roles in the flowering process ranging from floral initiation to the development of floral organs
Various transcription factors are essential in regulating these developmental processes, including the family of MADS-box transcription factors
Molecular evolutionary analysis of soybean MIKCc-type MADS-box transcription factors When we searched the soybean predicted gene set available at Phytozome [12] for sequences containing both a MADS-box and K-domain, we identified a total of 57 sequences

Summary

Introduction

The classical (C) MIKC-type MADS-box transcription factors comprise one gene family that plays diverse roles in the flowering process ranging from floral initiation to the development of floral organs. Despite their importance in regulating developmental processes that impact crop yield, they remain largely unexplored in the major legume oilseed crop, soybean. The MADS-box transcription factors, especially the plant-specific classical (C) MIKC-type MADS-box genes, are known to play key regulatory roles in different stages of flower development Their roles in coordinating floral developmental processes have been revealed by functional studies largely carried out in the model plant, Arabidopsis thaliana. The highly conserved MADS-domain and the weakly conserved I-domain are required for DNA binding, while the strongly conserved K-domain and the variable Cdomain regulate protein interactions [1]

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