Phylogenetic analysis of the genus Petunia (Solanaceae) based on the sequence of the Hf1 gene

Abstract

Polymerase chain reaction fragment length polymorphisms and nucleotide sequences for a cytochrome P450 gene encoding flavonoid-3',5'-hydroxylase, Hf1, were studied in 19 natural taxa of Petunia. Natural Petunia taxa were classified into six groups based on major insertion or deletion events that occurred only in intron II of the locus. The maximum parsimony method was used to calculate strict consensus trees based on nucleotide sequences in selected regions of the Hf1 locus. Petunia taxa were divided into two major clades in the phylogenetic trees. Petunia axillaris (including three subspecies), P. exserta, and P. occidentalis formed a clade with 100% bootstrap support. This clade is associated with a consistently inflexed pedicel, self-compatibility in most taxa, and geographical distribution in southern and western portions of the genus range. The other clade, which comprised the remainder of the genus is, however, less supported (up to 71% bootstrap); it is characterized by a deflexed pedicel in the fruiting state (except P. inflata), self-incompatibility, and a northeastern distribution. A nuclear gene, Hf1, seems to be a useful molecular marker for elucidating the phylogeny of the genus Petunia when compared with the nucleotide sequence of trnK intron of chloroplast DNA.

Reconstructing Historical Events that Occurred in the Petunia Hf1 Gene, which Governs Anthocyanin Biosynthesis, and Effects of Artificial Selection by Breeding

“…We attempted to detect intact Hf1 genes of these putative historical parents, Hf1a and Hf1i, among current commercial petunias. The natural species of the genus Petunia were classified into six groups, according to the indels in the intron II sequences (Chen et al 2007). Hf1a was characterized by an approximately 2.1-kbp DNA fragment amplified from intron II (Fig.…”

“…In a phylogenetic study of natural taxa of Petunia based on the Hf1 sequence (Chen et al 2007), all the five nucleotides assigned to 'A' provided parsimony information for the formation of a clade with 100% bootstrap support including group 6 species such as AXI and PRD (Table 3). This clade was separated from another clade that included group 1 species such as INT and INF.…”

“…AB196180) differed from that of Hf1i at only one position and one indel (INT) or one position (INF), but differed from that of Hf1a at 12 positions and five indels (data not shown). For intron II, the Hf1c sequence (808 bp in length) was aligned with that of Hf1i (805 bp in length; Chen et al 2007) to reveal differences at 15 (INT) or 10 (INF) positions and five indels. However, the Hf1c intron II sequence and its length were too different from those of Hf1a (2344 bp in length; Chen et al 2007) to allow for reliable alignment (data not shown).…”

“…Previously, we identified the nucleotide sequences of the Hf1 loci of all the Petunia taxa except for a recently described species, P. secreta Stehmann & Semir. The natural species can be classified into six groups based on insertion/deletion events that occurred at the Hf1 intron II, and the length of intron II ranges from 582-584 bp (group 5 species) to 2041-2363 bp (group 6 species; Chen et al 2007). Therefore, we expected to find intact Hf1 genes derived from historical parents among various commercial petunias using PCR length polymorphisms.…”

“…Our objective was to reconstruct the historical events that occurred at the Hf1 locus of commercial petunias in the course of breeding, with special emphasis on the origin of the dominant Hf1 gene, based on Hf1 gene sequences obtained in the present and previous studies (Matsubara et al 2005, Chen et al 2007. We provided evidence for the historical parents of commercial petunias, possible interallelic recombination and mutations that occurred at the Hf1 locus after interspecific hybridization, and complete removal of intact Hf1 genes of parental species by breeders prior to the development of modern commercial petunias.…”