GORDITA (AGL63) is a young paralog of the Arabidopsis thaliana Bsister MADS box gene ABS (TT16) that has undergone neofunctionalization

Abstract

SUMMARYMIKC-type MADS domain proteins are key regulators of flower development in angiosperms. B sister genes constitute a clade with a close relationship to class B floral homeotic genes, and have been conserved for more than 300 million years. The loss-of-function phenotype of the A. thaliana B sister gene ABS is mild: mutants show reduced seed coloration and defects in endothelium development. This study focuses on GORDITA (GOA, formerly known as AGL63), the most closely related paralog of ABS in A. thaliana, which is thought to act redundantly with ABS. Phylogenetic trees reveal that the duplication leading to ABS and GOA occurred during diversification of the Brassicaceae, and further analyses show that GOA has evolved under relaxed selection pressure. The knockdown phenotype of GOA suggests a role for this gene in fruit longitudinal growth, while over-expression of GOA results in disorganized floral structure and addition of carpel-like features to sepals. Given the phylogeny and function of other B sister genes, our data suggest that GOA has evolved a new function as compared to ABS. Protein analysis reveals that the GOA-specific 'deviant' domain is required for protein dimerization, in contrast to other MIKC-type proteins that require the K domain for dimerization. Moreover, no shared protein interaction partners for ABS and GOA could be identified. Our experiments indicate that modification of a protein domain and a shift in expression pattern can lead to a novel gene function in a relatively short time, and highlight the molecular mechanism by which neofunctionalization following gene duplication can be achieved.

Spatiotemporal Seed Development Analysis Provides Insight into Primary Dormancy Induction and Evolution of theLepidium DELAY OF GERMINATION1Genes

“…It is tempting to speculate that in L. papillosum, the two LepaDOG1a and LepaDOG1c proteins provide functional roles in dormancy regulation that are fulfilled by different splice variants of the single AtDOG1 gene (Bentsink et al, 2006;Nakabayashi et al, 2012) in the shrunken genome of Arabidopsis, which is characterized by extensive gene loss (Thomas et al, 2006;Oyama et al, 2008). Furthermore, polyploidization can form the basis for neofunctionalization or subfunctionalization of multiplied and retained genes (homeologs; Erdmann et al, 2010;Liu and Adams, 2010;Franzke et al, 2011), providing a mechanism for potentially diversified or more complex functions of the individual LepaDOG1 proteins in a putatively conserved dormancy mechanism. As outlined above, we propose that L. papillosum evolved by autopolyploidization or allopolyploidization from the very closely related L. oxytrichum (or its progenitor).…”

Endosperm and Nucellus Develop Antagonistically in Arabidopsis Seeds

“…Consistent with our marker line results, we detected TT16 mRNA in the proximal region of the nucellus of wild-type ovules at stages 2-V and 3-V ( Figures 4P to 4R) and in the ii1 at stage 3-V ( Figures 4Q and 4R). By contrast, we did not detect TT16 expression in double mutant ovules of tt16;goa (Figures 4S to 4U), with GOA being the closest paralog of TT16 (Erdmann et al, 2010;Prasad et al, 2010). As a positive control, we hybridized tt16;goa ovule sections with a HIS4 antisense probe and detected its characteristic patchy expression pattern in actively dividing cells (Figures 4V to 4X) (Blein et al, 2008).…”

“…GOA, the closest paralog of TT16, has been shown to regulate fruit growth and integument development (Erdmann et al, 2010;Prasad et al, 2010). To determine whether GOA plays a role in nucellus development, we analyzed the central longitudinal section of goa ovules and seeds.…”

The MADS29 Transcription Factor Regulates the Degradation of the Nucellus and the Nucellar Projection during Rice Seed Development

“…Wheat (Triticum aestivum) B sister is highly expressed in endothelium, but its function is still unknown (Yamada et al, 2009). Loss of function of another Arabidopsis B sister clade member GORDITA (GOA/AGL63) results in larger fruits due to stimulated cell expansion, whereas overexpression of GOA results in the smaller flower organs and shorter fruits (Erdmann et al, 2010;Prasad et al, 2010). In rice, MADS29, MADS30, and MADS31 are three members of B sister genes (Arora et al, 2007); however, the detailed expression pattern and functional data for them are scarce.…”