Identification of RAPD Markers Linked to Digestive Amylase Genes using Near Isogenic Lines of the Silkworm,Bombyx mori

Abstract

Digestive amylase has been identified as a useful marker for breeding in the silkwrom, Bombyx mori L (Lepidoptera: Bombycidae), due to its wide genetic divergence, its role in better digestibility and robustness. The low yielding indigenous B. mori breeds of tropics like India are characterized by high activity amylase genes controlled by Amy div or dv alleles, while the high yielding breeds of temperate origin are endowed with ‘null’ type (Amy dn) with low activity. For improving the digestibility and survival of temperate breeds of Japanese origin, Near Isogenic Lines (NILs) were developed introgressing the Amy div and dv alleles from the Donor Parents (DPs) into the genetic background of the Recurrent Parents (RPs) with ‘null’ type of amylase, which showed significant improvement in viability of the NILs. With the objective to know whether the amylase gene itself may confer higher survival by improving digestibility or some other closely linked genes flanking the amylase locus is responsible for better viability of the NILs, RAPD profiles among six B. mori breeds comprising of the DPs, RPs, and NILs developed through introgression of Amy div or dv alleles were analysed using 27 sets of RAPD primers. Out of the 27 primers, six (OPA01, OPA06, OPA09, OPA15, OPAH03, and OPAH05) showed RAPD products linked to the amylase genes of the DPs introgressed in the NILs, which were absent in their respective RPs. Three amplicons of 1584 bp, 1904 bp, and 1232 bp were specific to Amy div allele and one amplified product of 1776 bp was found to be linked with the Amy dv allele. Interestingly, two PCR products of 2628 and 1375 bp were associated with both Amy div and dv alleles. The results are discussed in light of further characterization of these amplified products leading to identification of DNA sequences that may be responsible for better digestibility and higher survival in B. mori.

Detection of a single nucleotide polymorphism (SNP) DNA marker linked to cocoon traits in the mulberry silkworm, Bombyx mori (Lepidoptera: Bombycidae)

“…Using this method, very active digestive amylase genes from Indian polyvoltine strains used as DPs were introgressed into the genetic background of high yielding bivoltine strains of temperate origin with a "null" type of amylase and NILs were developed with a DP type of amylase (Ashwath et al, 2001). Using these NILs, RAPD markers linked to the high activity digestive amylase genes in silkworm were identified (Ashwath et al, 2010) The other method, which is more generally used, is referred to as bulked segregant analysis (BSA), which relies on the use of segregating populations of F2. This method involves comparing two pooled DNA samples of individuals from a segregating F2 population originating from a single cross.…”

Differentially expressed genes in white egg 2 mutant of silkworm, Bombyx mori, at early embryo development stages

“…Eight generations proceeded by the selection procedure of the white egg as selecting phenotype. After eight generations, the recurrent parent recovery is assumed to be about 99.95%, retaining all normal black egg traits, while the donor parent genome is reduced to less than 0.05%, eliminating all the undesirable traits except the white egg 2 related genes (Ashwath et al, 2010). Theoretically, the near- isogenic line of white egg 2 mutant construction paves a high-efficiency way to investigate the differentially expressed genes between white egg 2 mutant and normal black egg strain joint with microarray analysis.…”

Amylase gene expression patterns in Helicoverpa armigera upon feeding on a range of host plants

“…This can be corroborated with the fact that amylases are active during non-feeding stages like pupa, adult and eggs of H. armigera (Kotkar et al, 2009) unlike proteinases, which are expressed when protein is ingested (Zhu et al, 2005). Although, amylases have been studied in Lepidopteran insects (Ashwath et al, 2010;Ngernyuang et al, 2011;Parthasarathy and Gopinathan, 2005) their expression and correlation to dietary compositions are relatively unknown.…”