Petaloidy and floral homeotic genes in <em>Hydrangea chinensis</em> (Hydrangeaceae)
Date Issued
2007
Date
2007
Author(s)
Chang, Tien-Hao
DOI
zh-TW
Abstract
The inflorescence of Hydrangeaceae plants is often aggregated as a pseudanthium, which contains enlarged sepals on peripheral flowers of the inflorescence. The flowers with these petaloid sepals are generally sterile and may play important roles in attracting pollinators. In order to understand the molecular mechanism for the petaloidy formation, floral organ identity genes of <em>Hydrangea chinensis</em> was identified and examined the expression patterns among different organs.
One A-class (<em>HycFL</em>), three B-class (<em>HycPI</em>, <em>HycAP3</em>, <em>HycTM6</em>), one C-class (<em>HycAG</em>) and one E-class (<em>HycMADS1</em>) floral homeotic genes were identified from <em>H. chinensis</em>, and all of the sequences show conserved C-terminal motifs for ABCE class genes, further confirmation for their identities were carried out by separate phylogenetic analyses. RT-PCR results show that the A class homolog <em>HycFL</em>, one B class homolog, <em>HycTM6</em>, and the E-class gene homolog <em>HycMADS1</em> have ubiquitous expression in all floral parts. Another B-class homolog, <em>HycAP3</em>, is expressed in petals, stamens, styles, and lower part of carpels, which is fused to part of normal sepals. In contrast, <em>HycPI</em> is highly expressed in petals and stamens, and weakly in lower part of carpels. The C-class gene homolog, <em>HycAG</em>, is expressed in the inner three whorls of flowers but the expression is higher in stamens and carpels.
Under Scanning Electromicroscope examination, the epidermal surfaces of cells on examined floral parts all have cuticular striation, while only adaxial epidermal cells of enlarged sepals show conical shape, a feature commonly found in the epidermal cells of a petal in other flowering plants. Such conical cell formation has been demonstrated to be controlled by a transcription factor, <em>MIXTA</em>, in <em>Antirrhnicum majus</em>. We have also successfully cloned <em>HycMYB1</em>, a homolog of <em>MIXTA</em>. The RT-PCR result shows that <em>HycMYB1</em> is highly expressed in enlarged sepals and much less in normal sepals and petals. Since HycFL, <em>HycTM6</em>, <em>HycMADS1</em> and <em>HycMYB1</em> are all expressed in enlarged sepals, they are the candidate genes involved in the formation of petaloid sepals of <em>Hydrangea chinensis</em>.
Subjects
MADS-box基因
華八仙
MIXTA
類
花瓣
MADS-box genes
Hydrangea
petaloid sturcture
Type
other
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