Resolution of sex chromosome constitution by genomic in situ hybridization and fluorescence in situ hybridization with (TTAGG) n telomeric probe in some species of Lepidoptera

Abstract

We have developed a simple method to resolve the sex chromosome constitution in females of Lepidoptera by using a combination of genomic in situ hybridization (GISH) and fluorescence in situ hybridization with (TTAGG)( n ) telomeric probe (telomere-FISH). In pachytene configurations of sex chromosomes, GISH differentiated W heterochromatin and telomere-FISH detected the chromosome ends. With this method we showed that Antheraea yamamai has a standard system with a fully differentiated W-Z sex chromosome pair. In Orgyia antiqua, we confirmed the presence of neo-W and neo-Z chromosomes, which most probably originated by fusion of the ancestral W and Z with an autosome pair. In contrast to earlier data, Orgyia thyellina females displayed a neo-ZW(1)W(2) sex chromosome constitution. A neo-WZ(1)Z(2) trivalent was found in females of Samia cynthia subsp. indet., originating from a population in Nagano, Japan. Whereas another subspecies collected in Sapporo, Japan, and determined as S. cynthia walkeri, showed a neo-W/neo-Z bivalent similar to O. antiqua, and the subspecies S. cynthia ricini showed a Z univalent (a Z/ZZ system). The combination of GISH and telomere-FISH enabled us to acquire not only reliable information about sex chromosome constitution but also an insight into sex chromosome evolution in Lepidoptera.

Step-by-step evolution of neo-sex chromosomes in geographical populations of wild silkmoths, Samia cynthia ssp.

“…Recently, Peigler and Naumann (2003) reconstructed the genus and identified 19 different Samia species. Nevertheless, here we prefer the former classification of subspecies, which is consistent with that used in our previous cytogenetic study (see Yoshido et al, 2005b). In a previous study, we showed that three different geographic populations of S. cynthia exhibit a unique polymorphism in chromosome number, resulting from variations in the sex chromosome systems.…”

“…The majority of lepidopteran species show a WZ/ZZ (female/male) pair of sex chromosomes (reviewed by Traut et al (2007)). Besides the common WZ/ZZ system, variants without the W chromosome (Z/ZZ) and with multiple sex chromosomes, such as W 1 W 2 Z/ZZ and WZ 1 Z 2 /Z 1 Z 1 Z 2 Z 2 , have been found (for example, Nilsson et al, 1988;Traut and Marec, 1997;Yoshido et al, 2005b). The multiple sex chromosome systems may have originated from either fission or sex chromosome-autosome fusions (Marec et al, 2010).…”

“…The latter scenario, giving rise to neo-sex chromosomes, seems to be common not only in vertebrates (Toder et al, 1997;Schmid et al, 2003), but also in some insects, such as flies of the genus Drosophila (Flores et al, 2008) and true bugs of the genus Dysdercus (Bressa et al, 2009). This scenario is also more likely the source of multiple sex chromosomes in Lepidoptera (Yoshido et al, 2005b; reviewed by Marec et al (2010)). …”

The fate of W chromosomes in hybrids between wild silkmoths, Samia cynthia ssp.: no role in sex determination and reproduction

“…Two subspecies were collected at respective sites in 2005-2011 and reared on Alianthus altissima at the Field Science Center for Northern Biosphere (Hokkaido University, Sapporo, Japan; Yoshido et al, 2005Yoshido et al, , 2013.…”

“…indet. (Nagano, Japan) with 2n = 25♀/26♂, and neo-Wneo-Z/neo-Zneo-Z in S. c. walkeri (Sapporo, Japan) with 2n = 26♀/26♂ (Yoshido et al, 2005(Yoshido et al, , 2011a(Yoshido et al, , 2013. The variations in the constitution of sex chromosomes were derived from the loss of W chromosome and fusion between the sex chromosomes and autosomes, resulting in different chromosome numbers (Yoshido et al, 2011a, b;Sahara et al, 2012).…”