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    

Abstract

The products of B class floral homeotic genes specify petal and stamen identity, and loss of B function results in homeotic conversions of petals into sepals and stamens into carpels. Here, we describe the molecular characterization of seirena-1 (sei-1), a mutant from the basal eudicot California poppy (Eschscholzia californica) that shows homeotic changes characteristic of floral homeotic B class mutants. SEI has been previously described as EScaGLO, one of four B class-related MADS box genes in California poppy. The C terminus of SEI, including the highly conserved PI motif, is truncated in sei-1 proteins. Nevertheless, like the wild-type SEI protein, the sei-1 mutant protein is able to bind CArG-boxes and can form homodimers, heterodimers, and several higher order complexes with other MADS domain proteins. However, unlike the wild type, the mutant protein is not able to mediate higher order complexes consisting of specific B, C, and putative E class related proteins likely involved in specifying stamen identity. Within the PI motif, five highly conserved N-terminal amino acids are specifically required for this interaction. Several families lack this short conserved sequence, including the Brassicaceae, and we propose an evolutionary scenario to explain these functional differences.

Deciphering the Physalis floridana Double-Layered-Lantern1 Mutant Provides Insights into Functional Divergence of the GLOBOSA Duplicates within the Solanaceae

“…A presence of PFGLO1 genomic fragment in the doll1 background completely restored both the wild-type floral phenotypes and the expression of all detected MADS-box genes, including PFAG. However, our findings are contrary to studies that showed activation of AG by AP3 and/or PI in Arabidopsis (Bowman et al, 1991;Wuest et al, 2012) and that demonstrated that the C-function gene AG2 is reduced in the seirena1 mutant, a GLO mutant in California poppy (Eschscholzia californica; Lange et al, 2013). Therefore, transcriptional regulation of AG homologs by GLO proteins should be considered to be variable among angiosperms.…”

“…PFSEP3, a SEPALLATA-like protein, is required for normal floral organ development (Pelaz et al, 2000;Immink et al, 2009). However, the direct interactions between B-class proteins and E-class (PFSEP3) proteins were observed in tomato (Solanum lycopersicum) but not in Arabidopsis, Antirrhinum majus, Petunia hybrida, or Eschscholzia californica (Davies et al, 1996;Vandenbussche et al, 2004;de Folter et al, 2005;de Martino et al, 2006;Leseberg et al, 2008;Lange et al, 2013), indicating that the dimerization pattern of the homeotic orthologous proteins is variable among angiosperms. However, our findings on protein-protein interactions provide a common basis underlying the role of PFGLO1 and PFGLO2 in floral development in Physalis floridana.…”

Ultrastructure and optics of the prism‐like petal epidermal cells of Eschscholzia californica (California poppy)

“…Despite considerable ongoing interest in floral organ identity in early‐divergent eudicots such as Eschscholzia (e.g. Lange et al ., 2013), little is currently known about the developmental genetics of flower colour in this genus. Our results highlight the diverse range of strategies adopted by petals of different species to enhance colour and reflectivity, even among relatively closely related species.…”

The Maize PI/GLO Ortholog Zmm16/sterile tassel silky ear1 Interacts with the Zygomorphy and Sex Determination Pathways in Flower Development

“…The ABCE model predicts that third whorl organs of B class mutants will express C class genes alone and thus assume a carpel identity. Since sts1 mutants produce lemma/palea-like organs in the third whorl, one possibility is that C class gene expression is reduced in the third whorl of sts1 mutants, possibly as a result of a positive regulation of C class expression by B class genes, as has been seen in several ranunculids (Gonçalves et al, 2013;Lange et al, 2013). Under this scenario, we would expect to see a reduction in C class gene expression in the third whorl of sts1 male florets.…”