Abstract
The mechanism of sex determination is common for all honeybee species (Apis spp.) by the complementary sex determi-nation (csd) gene. The csd gene has been studied in the Western honey bee (Apis mellifera L.), the Eastern honey bee (Apis cerana F.) and the giant honey bee (Apis dorsata F.), whereas no studies had been conducted on the high altitude Himalayan or black giant honey bee, Apis laboriosa Smith. In the present study, we cloned the genomic exon 6 to exon 9 region of the A. laboriosa csd gene, and identified 13 csd haplotypes. The data was analyzed and compared with the other aforementioned three honeybee species. The results showed that, as with the other three Apis species, region 3 of the csd gene contains an RS domain at the N terminal, a proline-rich domain at the C terminal, and a hypervariable region in the middle. A phylogenetic tree showed that the csd haplotypes from A. laboriosa fell into one clade with those from A. dorsata, and were separated from those from the other two species, A. mellifera and A. cerana. The network map also showed that the csd haplotypes from A. laboriosa and A. dorsata are well mixed among each other, and do not form two separate branches. Pairwise Fst analysis revealed that the value between A. laboriosa and A. dorsata was very low (0.098), confirming a close relationship to exist between them.
Highlights
IntroductionSex is determined by heterozygosity at a single locus (the Sex Determination Locus, SDL) which carries the complementary sex determiner (csd) gene (Gempe et al, 2009)
In the honeybee, sex is determined by heterozygosity at a single locus which carries the complementary sex determiner gene (Gempe et al, 2009)
The polymorphism of the A. laboriosa csd gene was significantly higher than the polymorphism of A. cerana csd gene, but failed to be significant compared with values of the other two full species, including A. dorsata s.s
Summary
Sex is determined by heterozygosity at a single locus (the Sex Determination Locus, SDL) which carries the complementary sex determiner (csd) gene (Gempe et al, 2009). Beye et al (2003) cloned the csd gene from Apis mellifera by positional cloning They found that no transcription differences existed between the two sexes, but suppression of csd in females with double stranded RNA for csd resulted in male phenotypes. The exon 6 to exon 9 region of the csd gene has an R (arginine)- and S (serine)-rich domain in the middle and a P (proline)-rich domain at its C terminus, which is a potential splicing factor Between these two domains is a hypervariable region that differs significantly between alleles, and has a variable region of short repetitive sequences (Beye et al, 2003; Cho et al, 2006; Wang et al, 2012)
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