The CRABS CLAW ortholog from California poppy (Eschscholzia californica, Papaveraceae), EcCRC, is involved in floral meristem termination, gynoecium differentiation and ovule initiation

Abstract

Summary The Arabidopsis transcription factor CRABS CLAW (CRC) is a major determinant of carpel growth and fusion, and, in concert with other redundantly acting genes, of floral meristem termination. Its rice ortholog, however, has additional functions in specifying carpel organ identity. We were interested in understanding the history of gene function modulation of CRC‐like genes during angiosperm evolution. Here, we report the identification and functional characterization of EcCRC, the Californica poppy (Eschscholzia californica) CRC ortholog. The downregulation of EcCRC by virus‐induced gene silencing (VIGS) produces additional organ whorls that develop exclusively into gynoecia, resulting in a reiteration of the fourth whorl. Additionally, defects in carpel polarity and ovule initiation are apparent, and the observed phenotype is restricted to the gynoecium. Our results further show that the history of CRC‐like genes during angiosperm evolution is characterized by gains of function, independent of duplication processes in this gene subfamily. Moreover, our data indicate that the ancestral angiosperm CRC‐like gene was involved in floral meristem termination and the promotion of abaxial cell fate in the gynoecium, and that in the lineage leading to Arabidopsis, additional genes have been recruited to adopt some of these functions, resulting in a high degree of redundancy.

Functional Analysis of All AGAMOUS Subfamily Members in Rice Reveals Their Roles in Reproductive Organ Identity Determination and Meristem Determinacy

“…Furthermore, the dl phenotype did not change in the dl mads13 double mutant, whereas the loss of FM determinacy seen in dl flowers was strongly enhanced in the dl mads3 double mutant (Li et al, 2011b), most likely due to the simultaneous repression of MADS3 and MADS13. These data therefore suggest that the main function of DL in carpel development is to repress the B-function genes ( Figure 5), a function that its Arabidopsis ortholog CRABS CLAW (CRC), and its ortholog in the basal eudicot E. californica, EcCRC, do not have (Alvarez and Smyth, 1999;Bowman and Smyth, 1999;Orashakova et al, 2009). However, these studies clearly indicate that in basal and core eudicots, the CRC-like genes regulate important aspects of carpel morphogenesis.…”

TheseirenaB Class Floral Homeotic Mutant of California Poppy (Eschscholzia californica) Reveals a Function of the Enigmatic PI Motif in the Formation of Specific Multimeric MADS Domain Protein Complexes

“…Expression was measured with three technical replicates for each of the two biological replicates. In situ hybridization of SEI transcripts was performed on sections of floral buds of consecutive developmental stages with DIGlabeled probe encompassing nucleotides 509 of the SEI coding sequence to nucleotide 53 into its 39UTR (198 nucleotides total length) as described earlier (Orashakova et al, 2009). The California poppy AG in situ hybridization experiments were performed as described by Yellina et al (2010).…”

Time to Stop: Flower Meristem Termination

“…Thus, CRC, which specifically controls the female developmental program and is expressed from stage 6 on (Bowman and Smyth, 1999), also shares AG's function in FM termination, hence confirming the close link between these two processes. In the case of CRC, both functions seem to be widely conserved in angiosperms, as orthologs of CRC in various species display similar expression patterns in carpel primordia and loss-of-function phenotypes (Nagasawa et al, 2003;Yamaguchi et al, 2004;Fourquin et al, 2005;Lee et al, 2005;Orashakova et al, 2009). In rice, tobacco, petunia, and California poppy (Eschscholzia californica), this loss of function alone is sufficient to cause a strong loss of FM termination, suggesting that CRC orthologs play a more important role in this process in most species compared to Arabidopsis (Yamaguchi et al, 2004;Lee et al, 2005;Orashakova et al, 2009).…”