Abstract
The identification of mutants in model plant species has led to the isolation of the floral homeotic function genes that play crucial roles in flower organ specification. However, floral homeotic C-function genes are rarely studied in basal eudicots. Here, we report the isolation and characterization of the AGAMOUS (AG) orthologous gene (PaAG) from a basal eudicot London plane tree (Platanus acerifolia Willd). Phylogenetic analysis showed that PaAG belongs to the C- clade AG group of genes. PaAG was found to be expressed predominantly in the later developmental stages of male and female inflorescences. Ectopic expression of PaAG-1 in tobacco (Nicotiana tabacum) resulted in morphological alterations of the outer two flower whorls, as well as some defects in vegetative growth. Scanning electron micrographs (SEMs) confirmed homeotic sepal-to-carpel transformation in the transgenic plants. Protein interaction assays in yeast cells indicated that PaAG could interact directly with PaAP3 (a B-class MADS-box protein in P. acerifolia), and also PaSEP1 and PaSEP3 (E-class MADS-box proteins in P. acerifolia). This study performed the functional analysis of AG orthologous genes outside core eudicots and monocots. Our findings demonstrate a conserved functional role of AG homolog in London plane tree, which also represent a contribution towards understanding the molecular mechanisms of flower development in this monoecious tree species.
Highlights
The molecular mechanism of flower development has been the subject of intensive investigation over the last two decades
In order to isolate the putative floral homeotic C function gene of P. acerifolia, degenerate primers were designed within the conserved MADS domain and K domain through nucleotide alignments of various known AG orthologous gene sequences
Analysis of Platanus acerifolia AGAMOUS (PaAG) sequences revealed that the genome of P. acerifolia contains at least two PaAG gene copies, PaAG-1 and
Summary
The molecular mechanism of flower development has been the subject of intensive investigation over the last two decades. The classical ‘ABC’ model of flower development was proposed [1,2], and this has subsequently been expanded to the ‘ABCDE’ model [3,4,5]. In this latter model, five classes of floral homeotic function genes are recognized as responsible for determining floral organ identity by acting in a combinatorial fashion. Flowers with strong ag mutant phenotypes show the complete homeotic conversion of stamens into petals and carpels into sepals. These mutant lines show indeterminacy of the floral meristem. C-function genes are rarely studied in basal eudicots
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