FAN, CHUANZHU* and (Jenny) Qiu-Yun Xiang. Department of Botany, North Carolina State University, Campus box 7612, Raleigh, NC 27695-7612. - Sequence variation of flower anthocyanin regulatory gene in dwarf dogwoods (Cornus L. Cornaceae) - Potential utility in studying gene evolution in hybrids and polyploids.
Regulatory genes represent a class of loci that control the expression
of other genes. It is well-known that regulatory gene evolution is a
significant factor in organismal diversification. Thus, the studies of
regulatory gene evolution in plant may provide clues on the
morphological differentiation and ecological adaptation. Plants
display remarkable diversity in the pattern and intensity of red or
purple anthocyanin pigmentation in vegetative and floral organs.
Mutations that stop anthocyanin production can be controlled by
regulators of the biosynthetic genes, which occur as a gene family in
the diverse plant species. Morphological analysis of the dwarf dogwood
species complex (Cornus subgen. Arctocrania) suggested
extensive hybridization occurred between two evolutionary diverged
species (C. canadensis and C. suecica), which may have
led to the formation of two hybrid lineages (C.
canadensis>C. suecica, and C. suecica>C.
canadensis) and one allo-tetraploid species (C.
unalaschkensis). The five taxa in the complex exhibit variation in
the color of petals, which provides an excellent system to study
molecular evolution and speciation following hybridization and
polyploidization using flower pigmentation regulatory genes. We
investigate the homologs of R gene family which regulates the red
anthocyanin pigmentation in plants. A portion of 750bp of this gene in
the exon 1, 2 and intron 1 regions has been amplified, cloned and
sequenced for samples representing different putative taxa. Two types
of sequences (referred to as “a” and “b”) were identified, which have
alignable exon regions, but are highly divergent in the intron region.
There are sequence variations in both exon and intron regions in both
“a” and “b” types among different populations sequenced. This
preliminary data suggested that anthocyanin regulatory gene is a
potential marker to study the gene evolution following hybridization
and polyploidization in plants. The pattern of sequence variation and
its correlation with petal color will be discussed.
Key words: Anthocyanin regulatory gene, Cornus, Dwarf dogwoods, Gene evolution, Hybridization, Polyploidization