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Open Access Research

Understanding the basis of a novel fruit type in Brassicaceae: conservation and deviation in expression patterns of six genes

Mariano Avino1, Elena M Kramer2, Kathleen Donohue3, Alexander J Hammel1 and Jocelyn C Hall1*

Author Affiliations

1 Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, CANADA

2 Department of Organismal and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA

3 Department of Biology, Duke University, Durham, NC, 27708, USA

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EvoDevo 2012, 3:20  doi:10.1186/2041-9139-3-20

Published: 3 September 2012

Abstract

Background

Variation in fruit morphology is important for plant fitness because it influences dispersal capabilities. Approximately half the members of tribe Brassiceae (Brassicaceae) exhibit fruits with segmentation and variable dehiscence, called heteroarthrocarpy. The knowledge of the genetics of fruit patterning in Arabidopsis offers the opportunity to ask: (1) whether this genetic pathway is conserved in taxa with different fruit morphologies; (2) how the pathway may be modified to produce indehiscence; and (3) whether the pathway has been recruited for a novel abscission zone.

Methods

We identified homologs of ALCATRAZ, FRUITFULL, INDEHISCENT, SHATTERPROOF, and REPLUMLESS from two taxa, representing different types of heteroarthrocarpy. Comparative gene expression of twelve loci was assessed to address how their expression may have been modified to produce heteroarthrocarpy.

Results

Studies demonstrated overall conservation in gene expression patterns between dehiscent segments of Erucaria erucarioides and Arabidopsis, with some difference in expression of genes that position the valve margin. In contrast, indehiscence in heteroarthrocarpic fruit segments was correlated with the elimination of the entire valve margin pathway in Erucaria and Cakile lanceolata as well as its absence from a novel lateral abscission zone.

Conclusions

These findings suggest that modifications in the valve margin positioning genes are responsible for differences between heteroarthrocarpic and Arabidopsis-like fruits and support the hypothesis that heteroarthrocarpy evolved via repositioning the valve margin. They also highlight conservation in the dehiscence pathway across Brassicaceae.

Keywords:
ALCATRAZ; Brassicaceae; Fruit development; INDEHISCENT; FRUITFULL; REPLUMLESS; SHATTERPROOF; Silique