Evolution and phylogenetic utility of the period gene in Lepidoptera

Abstract

Evolution and phylogenetic utility of the period gene are explored through sequence analysis of a relatively conserved 909-bp fragment in 26 lepidopteran species. Taxa range from tribes to superfamilies, primarily within the putative clade Macrolepidotera plus near outgroups, and include both strongly established and problematic groupings. Their divergence dates probably range from the late Cretaceous through much of the Tertiary. Comparisons within the same set of closely related species show that amino acid substitutions in period occur 4.9 and 44 times as frequently as they do in two other nuclear genes--dopa decarboxylase and elongation factor-1 alpha, respectively. In contrast, rates of observed synonymous substitution are within 60% of each other for these three genes. Synonymous changes in period approach saturation by the family level, whereas nonsynonymous and amino acid divergences across the Macrolepidoptera are less than half the maximal values reported for this gene. Phylogenetic analyses of period strongly supported groupings at the family level and below. In contrast to previous analyses at this level with other nuclear genes, much of the information lies in nonsynonymous change. Relationships up to the superfamily level were recovered with decreasing effectiveness, and little, if any, signal was apparent regarding relationships among superfamilies. This could reflect rapid radiation of the superfamilies, however, rather than saturation in the period locus; thus, period, in combination with other genes, remains a plausible candidate for approaching the difficult problems of lepidopteran family and superfamily relationships.

Neuroanatomical studies of period gene expression in the hawkmoth, Manduca sexta

“…The two immunoreactive peptides span slightly different regions of the consensus PER protein, but both include sequences flanking the site of the per s mutation, suggesting that the antibodies react with this well-conserved domain of PER (Reppert et al, 1994;Regier et al, 1998). Their reactivity with D. melanogaster PER was confirmed in immunocytochemical experiments, in which they labeled the usual per-expressing cells in wild-type flies (J.N.…”

“…Previous studies of PER expression in other insects have used anti-PER-S, an antiserum against a peptide just downstream of the per s mutation (Siwicki et al, 1988), a region that is well conserved among sequenced insect per homologs (Colot et al, 1988;Thackeray and Kyriacou, 1990;Reppert et al, 1994;Regier et al, 1998). In brains of a silkmoth, A. pernyi , a beetle, Pachymorpha sextaguttata (Frisch et al, 1996), and a cricket, Teleogryllus commodus (Honegger et al, 1991), anti-PER-S labeled the somata and projections of some dorsolateral neurosecretory cells.…”

“…These same three domains are conserved among insects: the period gene of the giant silkmoth Anthereae pernyi encodes a protein that bears 57, 48, and 73% identity, respectively, with the amino-terminal region, the PAS domain, and the per s region of Drosophila PER (Reppert et al, 1994). A phylogenetic analysis of the PAS domains and the per s regions of more than 20 lepidopteran period genes, however, indicates that even this most conserved region of per has evolved rapidly compared with other nuclear genes (Regier et al, 1998).…”

Molecular Cogs of the Insect Circadian Clock

“…The deduced sequence with 323 amino acids was judged to be the region corresponding to PAS domain from its similarity to those of other insect PERIOD PAS domains. When this amino acid sequence was compared with the sequence reported by Regier et al (1998), however, we found that the sequence of Bombyx mori PERIOD reported in the database contained an additional five amino acid residues in this PAS domain. The insertion/deletion of GTQEK pentapeptide was found between the Asn(=N) and Ala(=A) residues in a proline-truncated site PKTANAQSP.…”

“…This 15 bp nucleotide sequence corresponds to the amino acid sequence GTQEK. PAS domain sequences are highly conserved among the various insect PERIOD homologues (Regier et al ., 1998). When we aligned the sequence of PAS domains very carefully, however, the domains were classified into two groups: namely, PAS domains with GTQEK or a related pentapeptide and PAS domains lacking such a fragment (Fig.…”