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Chromosome Pairing and Fertility in Plant Hybrids
Published in Christopher B. Gillies, Fertility and Chromosome Pairing: Recent Studies in Plants and Animals, 2020
Fully fertile, interspecific hybrids rarely occur in nature because barriers have evolved which either prevent species from hybridizing in the first place, or which confer on the hybrid some degree of selective disadvantage in terms of fertility or viability. The inability of pollen of one species to fertilize the ovules of another is an obvious way in which hybridization is prevented in plants. However, even if fertilization is successful, the viability of the hybrid embryo may be impaired by some incompatibility between the embryo and the maternal tissue, or perhaps failure in the development of the endosperm. If the hybrid manages to reach sexual maturity, it may be that the sex organs are abnormal (diplontic sterility) due to an imbalance in the nuclear genes or to a detrimental interaction between the hybrid nucleus and cytoplasm. An example of the latter is found in the hybrid between Epilobium luteum and E. hirsutum, which produces 15 to 20% viable pollen when E. luteum is the maternal parent.1 The reciprocal cross, however, is completely sterile. In addition, the gametes themselves may be imbalanced by incompatible gene combinations which render them incapable of producing a hybrid zygote (haplontic sterility).
Genetic and Developmental Implications for Trace Metal metabolism from Mutant and Inbred Strains of Animals
Published in Owen M. Rennert, Wai-Yee Chan, Metabolism of Trace Metals in Man, 2017
Since the findings of two excellent laboratories could not be more contradictory, I proposed that there must be a genetic explanation for their different findings. Each laboratory, however, attributed the source of the cr mice to the same hybrid stock from the Jackson Laboratory. Hurley referred to her stock as B6C3F. (Conventionally geneticists have abbreviated the inbred strain designations in reference to some standard F1 hybrid strains. In this case B6C3F1 would have referred to a cross involving F1 progeny from C57BL/6J females by C3H/HeJ males; progeny from the reciprocal cross, C3H/HeJ females by C57BL/6J males, would have been indicated by C3B6F1.) In contrast to Hurley’s reference, Mann et al.142 referred to their stock as a hybrid between C3H and C57BL/6J, which as noted above would be a reciprocal cross to that of Hurley’s stock. Nevertheless, these differences in designation seem inconsequential because the only cr stock available from Jackson since 1972 has been a B6C3-a/a + /cr stock. This was obtained by backcrossing cr into a special B6C3-a/a F1 (C57BL/6J dam × C3HeB/FeJ-a/a sire) hybrid strain for several generations (N = 17 in 1981).143
Xenogeneic Donkey-In-Horse Pregnancy Created by Embryo Transfer
Published in Gérard Chaouat, The Immunology of the Fetus, 2020
W. R. Allen, Julia H. Kydd, D. F. Antczak
All the member species of the genus Equus can be interbred to produce live, although usually sterile, hybrid offspring.40 The mule (2n = 63; ♀ horse × ♂ donkey) and the reciprocal cross, the hinny (2n = 63; ♀ donkey × ♂ horse), are the two most common of these manmade equine hybrids,41 and they provide a striking illustration of the influence of fetal genotype on maternal antifetal immune responses during early pregnancy. In the mare carrying an interspecific mule conceptus, for example, the endometrial cups are narrower and generally smaller than those in a mare carrying a normal intraspecies horse conceptus. Very large numbers of lymphocytes are attracted to the endometrial cups within a few days after invasion of the endometrium by the chorionic girdle and, instead of remaining clustered at the periphery of the cup, the lymphocytes immediately begin to invade the cup tissue. This results in premature necrosis and sloughing of the cups by as early as Days 60 to 70 of gestation (Figure 7a), thereby leading to an early disappearance of eCG from maternal blood. In the jenny donkey carrying the hinny conceptus, on the other hand, very much larger endometrial cups develop compared to those found in intraspecific donkey pregnancies. As in the mare carrying the mule, the maternal lymphocyte response to the cups is markedly increased. But instead of invading the cup tissue at the outset, the accumulated leukocytes remain as a dense band at the periphery until Day 70 to 80 in a similar manner to the cups in intraspecies horse pregnancies (Figure 7b).15 These larger and more active endometrial cups give rise to very high concentrations of eCG in the serum of donkeys carrying hinny conceptuses.42 This results in hyperStimulation and excessive luteinization of the maternal ovaries so that peripheral plasma progesterone concentrations reach values as high as 100 to 600 ng/ml between Days 50 and 100 of gestation.43,44
Cellular mechanisms regulating synthetic sex ratio distortion in the Anopheles gambiae germline
Published in Pathogens and Global Health, 2020
Roya Elaine Haghighat-Khah, Atashi Sharma, Mariana Reis Wunderlich, Giulia Morselli, Louise Anna Marston, Christopher Bamikole, Ann Hall, Nace Kranjc, Chrysanthi Taxiarchi, Igor Sharakhov, Roberto Galizi
To date, the cellular mechanisms following selective breakage and selection of sex chromosomes, which results in male-biased progeny, remains elusive for both naturally occurring and synthetic mosquito SD systems. In a previous study, Ae. aegypti males carrying the naturally occurring SD produced 29% fewer spermatozoa compared to the wild-type males of a reciprocal cross, indicating a possible meiotic checkpoint responsible for detecting and removing damaged X-sperm, though not by enough to explain the resulting male bias with just 3.8% of females being generated [2]. Synthetic A. gambiae SD males, such as Ag(PMB)1, produce highly male biased progenies without a reduction in the total number of individuals generated [9,11].
Women in science: a son’s perspective
Published in Journal of Neurogenetics, 2021
My mom’s research program really began when she was an undergraduate student in 1976 doing a project for a developmental genetics course. At the time, she was inspired by animal behavior and genetics as separate entities. In her undergraduate course, she designed a project to study the behavior of Drosophila melanogaster larvae. She discovered that some larvae tended to move a lot while foraging for food, while others moved relatively little. She called these larvae ‘rovers’ and ‘sitters’ respectively, before mapping the phenomena to the second pair of autosomal chromosomes. Her efforts earned her a B + because she was trying to study behavior and not development. As it turns out, this initial discovery leads to her first paper (Sokolowski, 1980) and her life’s work. A decade later, my mom and her first Ph.D. student, Steve de Belle, used a sixteen reciprocal cross procedure to reveal that the rover/sitter larval locomotory phenotype followed a Mendelian, autosomal dominant inheritance pattern (de Belle & Sokolowski, 1987). She then needed to get creative to profile foraging because full genome sequencing techniques to localize normal individual differences in behavior were not yet available. Two years later, she and her collaborators published a novel genetic method called lethal tagging to locate foraging (de Belle, Hilliker, & Sokolowski, 1989). Their subsequent long and challenging chromosome walk resulted in cloning the first gene for normal individual differences in behavior in any organism (Osborne et al., 1997). In this paper, they discovered that foraging encodes cGMP-dependent protein kinase (PKG) and that increasing foraging cDNA could convert the behavior of a sitter into a rover (Osborne et al., 1997). In the following twenty years, the Sokolowski lab studied the pleiotropic effects of the foraging gene and their foraging null generated through homologous recombination to display dosage effects on rover/sitter differences in other patterns of locomotion, food intake, and fat levels (Allen, Anreiter, Neville, & Sokolowski, 2017; Anreiter & Sokolowski, 2019). While characterizing foraging, my mom leveraged the pleiotropy and molecular tools she built and adapted to use foraging as a model to learn more about the fundamentals of behavior, evolution, development, and molecular biology. With foraging as her anchor, my mom, her team, and her collaborators identified clear and ecologically relevant biological phenomena. Some of these discoveries include the density-dependent and negative frequency-dependent selection effects on the foraging gene (Fitzpatrick, Feder, Rowe, & Sokolowski, 2007; Sokolowski, Pereira, & Hughes, 1997), and studies of the function of the foraging gene in eusocial insects (Ben-Shahar, Robichon, Sokolowski, & Robinson, 2002; Lucas & Sokolowski, 2009). When looking inward to the function of foraging, she has mapped phenotypes to tissue-specific, promoter-specific, and isoform-specific alterations in gene expression and epigenetics.