Genome-Wide Identification and Expression Profiling of Wnt Family Genes in the Silkworm, Bombyx mori

Abstract

Wnt is a family of conserved glycoproteins that participate in a variety of important biological processes including embryo development, cell proliferation and differentiation, and tissue regeneration. The Wnt family is a metazoan novelty found in all animal phyla. Studies have revealed that the number of Wnt genes varies among species, presumably due to reproduction and loss of genes during evolution. However, a comprehensive inventory of Wnt genes in Lepidoptera is lacking. In this study, we identified the repertoire of Wnt genes in the silkworm and seven other species of Lepidoptera and obtained eight Wnt genes (Wnt1, Wnt5–Wnt7, Wnt9–Wnt11, and WntA) in each species. Four of these Wnt genes are clustered in two orientations (5′-Wnt9-Wnt1-Wnt6-Wnt10-3′ and 5′-Wnt10-Wnt6-Wnt1-Wnt9-3′) in both moths and butterflies. Transcript analysis of Wnt in silkworm embryonic stages showed that each BmWnt gene had a unique expression pattern during embryological development. Analysis of a larval stage revealed differential expression of Wnt family members in diverse tissues. Our study provides an overview of the Wnt family in Lepidoptera and will inspire further functional study of the Wnt genes in the silkworm.

Wnt Gene Expression During Early Embryogenesis in the Nymphalid Butterfly Bicyclus anynana

“…Despite missing sequences for eight of our focal species, it seems very likely that eight Wnt genes is the ancestral ditrysian Wnt repertoire. These results are consistent with the previously published Wnt repertoire for B. mori (Ding et al, 2019). This could indicate that eight Wnt genes were also present in the common ancestor of all lepidopterans including non-ditrysian species, but further analysis of additional species is needed to verify this.…”

“…While Wnt5 is expressed at several embryonic stages in the nervous system in D. melanogaster (Fradkin et al, 1995(Fradkin et al, , 2004 and in e.g., limb buds, head lobes, and segmental stripes T. castaneum (Bolognesi et al, 2008a) we did not detect any expression for this Wnt gene in B. anynana. In a recent study of B. mori, Wnt5 transcripts were also only observed in very late embryonic stages (6 days AEL) as well as in larval tissues such as head, ovaries and the wing discs (Ding et al, 2019). Therefore, we propose, that Wnt5, contrary to Drosophila and Tribolium, is not expressed in the embryonic stages of Bicyclus included in this study.…”

“…Previously, seven Wnt subfamilies were described in the butterfly Heliconius melpomene (Martin et al, 2012) and their expression was analyzed in larval wing discs (Martin and Reed, 2014). More recently, a study found representatives of eight subfamilies in several ditrysian butterfly and moth species (Ding et al, 2019). All used species in this study are part of the polyphyletic taxonomic suborder of the Ditrysia.…”

“…All used species in this study are part of the polyphyletic taxonomic suborder of the Ditrysia. However, embryonic Wnt gene expression has only been studied in the moths Bombyx mori (Ding et al, 2019) and Manduca sexta (Dow et al, 1988;Broadie et al, 1991;Miya, 2003).…”

Widespread retention of ohnologs in key developmental gene families following whole genome duplication in arachnopulmonates

“…Supplementary Table 1 for accession numbers, Supplementary Data File 1 for amino acid sequence alignments. (Janssen et al 2010); the insects D. melanogaster, T. castaneum (Bolognesi et al 2008) and B. anynana (Ding et al 2019;Holzem et al 2019); the crustacean Da. pulex (Janssen et al 2010); the myriapod S. maritima (Chipman et al 2014); and the onychophoran Eu.…”