Agrogen (Czechia)

Genetic disorders are usually considered to be caused by harmful gene mutations, as well as by chromosomal aberrations, including small insertions, duplications and/or deletions. However, as infertile individuals often arise among the offspring of crosses between two fertile mouse strains, we postulate that a certain combination of 'normal' genes with neither gene mutations nor chromosomal aberrations can cause such serious phenotypic alterations as reproductive dysfunction. In this study, we show evidence that a combination of multiple normal genes from two different normal mouse strains manifests a wide range of male reproductive dysfunctions, from benign changes to complete infertility. These abnormal phenotypes are thought to have occurred by epistatic interactions of alleles.

Bt toxins derived from the arthropod bacterial pathogen Bacillus thuringiensis are widely used for insect control as insecticides or in transgenic crops. Bt resistance has been found in field populations of several lepidopteran pests and in laboratory strains selected with Bt toxin. Widespread planting of crops expressing Bt toxins has raised concerns about the potential increase of resistance mutations in targeted insects. By using Bombyx mori as a model, we identified a candidate gene for a recessive form of resistance to Cry1Ab toxin on chromosome 15 by positional cloning. BGIBMGA007792-93, which encodes an ATP-binding cassette transporter similar to human multidrug resistance protein 4 and orthologous to genes associated with recessive resistance to Cry1Ac in Heliothis virescens and two other lepidopteran species, was expressed in the midgut. Sequences of 10 susceptible and seven resistant silkworm strains revealed a common tyrosine insertion in an outer loop of the predicted transmembrane structure of resistant alleles. We confirmed the role of this ATP-binding cassette transporter gene in Bt resistance by converting a resistant silkworm strain into a susceptible one by using germline transformation. This study represents a direct demonstration of Bt resistance gene function in insects with the use of transgenesis.