GENETIC ENHANCEMENT FOR RESISTANCE TO BIOTIC AND ABIOTIC STRESSES IN HARD WINTER WHEAT
Location: Hard Winter Wheat Genetics Research Unit
Title: A neo-sex-chromosome that drives post-zygotic sex determiniation in the Hessian fly
Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 11, 2009
Publication Date: March 1, 2010
Citation: Benatti, T., Valicente, R., Aggarwal, R., Zhao, C., Walling, J., Chen, M., Cambron, S.E., Schemerhorn, B.J., Stuart, J. 2010. A neo-sex-chromosome that drives post-zygotic sex determiniation in the Hessian fly. Genetics. 184:769-777.
Interpretive Summary: Hessian fly is a destructive pest of wheat and also a model organism to study Genetics and Plant/Insect Interactions. Hessian fly has four different types of sexes: male, female producing only female offspring, female producing only male offspring, and female producing both male and female. The genetics for determining these four types of sexes is not previously known. In this study, we found that two small regions of chromosome A1 are associated with sex determination through inversion. This research provides the foundation for further research that should lead to the cloning of the gene(s) that determine sex types. The finding enriches our understanding of the basic biology on the evolution of sex development from insects to higher organisms. This and future researches on this subject may also lead to practical application such as new pest management technologies based on affecting sex ratio of insects.
Two nonoverlapping autosomal inversions defined unusual neo-sex chromosomes in the Hessian fly (Mayetiola destructor). Like other neo-sex chromosomes, these were normally heterozygous, present only in one sex, and suppressed recombination around a sex-determining master switch. Their unusual properties originated from the anomalous Hessian fly sex determination system in which postzygotic chromosome elimination is used to establish the sex-determining karyotypes. This system permitted the evolution of a master switch (Chromosome maintenance, Cm) that acts maternally. All of the offspring of females that carry Cm-associated neo-sex chromosomes attain a female-determining somatic karyotype and develop as females. Thus, the chromosomes act as maternal effect neo-W's, or W-prime (W') chromosomes, where ZW' females mate with ZZ males to engender female-producing (ZW') and male-producing (ZZ) females in equal numbers. Genetic mapping and physical mapping identified the inversions. Their distribution was determined in nine populations. Experimental matings established the association of the inversions with Cm and measured their recombination suppression. The inversions are the functional equivalent of the sciarid X-prime chromosomes. We speculate that W' chromosomes exist in a variety of species that produce unisexual broods.