Functional analysis of B and C class floral organ genes in spinach demonstrates their role in sexual dimorphism

BMC Plant Biology

Research Article

Maja Jovanovic¹  Edward M Golenberg¹  D Noah Sather² 

[1] Department of Biological Sciences, Wayne State University, 48202, Detroit, MI, USA;Department of Biological Sciences, Wayne State University, 48202, Detroit, MI, USA;Current address: Seattle Biomedical Research Institute, 307 Westlake Avenue N, 98109, Seattle, WA, USA;

关键词: Floral Organ;    Female Flower;    Male Flower;    Organ Identity;    Male Plant;   

DOI  :  10.1186/1471-2229-10-46

 received in 2009-10-02, accepted in 2010-03-12,  发布年份 2010

来源: Springer

【 摘 要 】

BackgroundEvolution of unisexual flowers entails one of the most extreme changes in plant development. Cultivated spinach, Spinacia oleracea L., is uniquely suited for the study of unisexual flower development as it is dioecious and it achieves unisexually by the absence of organ development, rather than by organ abortion or suppression. Male staminate flowers lack fourth whorl primordia and female pistillate flowers lack third whorl primordia. Based on theoretical considerations, early inflorescence or floral organ identity genes would likely be directly involved in sex-determination in those species in which organ initiation rather than organ maturation is regulated. In this study, we tested the hypothesis that sexual dimorphism occurs through the regulation of B class floral organ gene expression by experimentally knocking down gene expression by viral induced gene silencing.ResultsSuppression of B class genes in spinach resulted in the expected homeotic transformation of stamens into carpels but also affected the number of perianth parts and the presence of fourth whorl. Phenotypically normal female flowers developed on SpPI-silenced male plants. Suppression of the spinach C class floral organ identity gene, SpAG, resulted in loss of reproductive organ identity, and indeterminate flowers, but did not result in additional sex-specific characteristics or structures. Analysis of the genomic sequences of both SpAP3 and SpPI did not reveal any allelic differences between males and females.ConclusionSexual dimorphism in spinach is not the result of homeotic transformation of established organs, but rather is the result of differential initiation and development of the third and fourth whorl primordia. SpAG is inferred to have organ identity and meristem termination functions similar to other angiosperm C class genes. In contrast, while SpPI and SpAP3 resemble other angiosperms in their essential functions in establishing stamen identity, they also appear to have an additional function in regulating organ number and identity outside of the third whorl. We present a model for the evolution of dioecy in spinach based on the regulation of B class expression.

【 授权许可】

Unknown   
© Sather et al; licensee BioMed Central Ltd. 2010. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.