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Research

Oncopeltus testis tip stained for S-phase (magenta), M-phase (green) and interphase (blue) nuclei

Research Interests I am a reproductive biologist who investigates how reproductive mechanisms interact with selection under variable physical and social environments.   I am particularly interested in the role of developmental mechanisms in sexual selection, sexual conflict and the evolution of reproductive strategies. My training is in cell and developmental biology and I collaborate with Professor Allen Moore and others in applying these tools to evolutionary questions. My lab uses a variety of approaches including manipulating gene expression using RNAi, microscopy, behavioral observations, and quantitative genetics to investigate these questions. My current research is centered on the function of the maintenance methyltransferase, DNMT1, in gametogenesis and fertility in insects.

Current Research Interests:

DNA methylation and fertility in insects

Given the importance of DNA methylation in protection of the genome against transposable elements and transcriptional regulation in other taxonomic groups, the diversity in both levels and patterns of DNA methylation in the insects raises questions about its function and evolution. In my lab we have shown that the maintenance DNA methyltransferase, DNMT1, affects meiosis and is essential to fertility in both male and female milkweed bugs, Oncopeltus fasciatus. DNA methylation is not required in somatic cells. Our results support a hypothesis that Dnmt1 is required for the transition of germ cells to gametes in O. fasciatus and that this function is conserved in male and female gametogenesis and further suggest that DNMT1 has a function independent of DNA methylation in germ cells. Our work raises the question of how a gene so critical in fitness across multiple insect species can have diverged widely across the insect tree of life. We are currently exploring the mechanisms by which Dnmt1 downregulation inhibits the transition of spermatocytes into spermatogonia.

Related papers:

(*with undergraduate students; †graduate students; ‡postdoctoral researchers)

Washington, J. T., *K. R. Cavender, *A. U. Amukamara, E. C. McKinney, R. J. Schmitz, & P. J. Moore. 2021. The essential role of Dnmt1 in gametogenesis in the large milkweed bug Oncopeltus fasciatus. eLife 10: e62202.

*Amukamara, A. U., *J. T. Washington, *Z. Sanchez, E. C. McKinney, A. J. Moore, R. J. Schmitz, & P. J. Moore. 2020. More than DNA methylations: does pleiotropy drive the complex pattern of evolution of Dnmt1? Frontiers in Ecology and Evolution 8: 4.

Bewick, A. J., *Z. Sanchez, E. C. Mckinney, A. J. Moore, P. J. Moore, & R. J. Schmitz. 2019. Dnmt1 is essential for egg production and embryo viability in the large milkweed bug, Oncopeltus fasciatus. Epigenetics & Chromatin 12: 6

Dnmt1 knockdown in larval female O. fasciatus results in a complete lack of oocytes (C) similar to what is seen when Boule, a conserved gene required for progression through meiosis (D) is knocked down in a similar stage of development.

Photo by Stephen Ausmus USDA

We have recently expanded the Dnmt1 project to investigate the potential for utilizing Dnmt1 as a target for an RNAi-based biocontrol strategy in the sweet potato whitefly, Bemisia tabaci. Often whiteflies cause economic damage to crop plants due to large population size. We are investigating the use of a soft selection strategy to keep population size in control while reducing the opportunity for resistance to evolve. We are investigating the use of RNAi-mediated reduction in Dnmt1 expression in reducing the speed of population growth by reducing fertility in the whitefly. Our experiments are focused on (1) demonstrating that the function of Dnmt1 in gametogenesis is conserved in B. tabaci and that downregulating Bt-Dnmt1 expression reduces reproductive potential in females and (2) documenting the impact of RNAi knockdown of Dnmt1 on population growth.

Past research interests:

Oncopeltus feed mostly on milkweed seeds in the wild. Credit: Judy Gallagher

My past research has focused on the role of developmental mechanisms in life history evolution.  My research has been centered on two areas, evolution of male reproductive strategies in different nutritional and social contexts and how early reproductive experiences shape lifetime reproductive success.

Plasticity under variable nutritional environments (selected publications):

†Duxbury, A., *B. Weathersby, *Z. Sanchez, and P. J. Moore. 2018. A study of the transit amplification divisions during spermatogenesis in Oncopeltus fasciatus to assess plasticity in sperm numbers or sperm viability under different diets.  Ecology and Evolution 8: 10460-10469.

In the lab, O. faciatus has adapted to utilize sunflower, but not pumpkin, seed as a food source.

†A. Attisano, T. Tregenza, A. J. Moore and P. J. Moore. 2013. Oosorption and migratory strategy of the milkweed bug, Oncopeltus fasciautus.  Animal Behaviour 86: 651-657.

†A. Attisano, A. J. Moore and P. J. Moore. 2012. Reproduction-longevity trade-offs reflect diet, not adaptation. Journal of Evolutionary Biology 25: 873-880

†Barrett, E.L.L.B., J. Hunt, A. J. Moore and P. J. Moore. 2009.  Effects of nutrition during juvenile and sexual development on female life-history trajectories: the thrifty phenotype in a cockroach. Proceedings of the Royal Society B: Biological Sciences 276: 3257-3264.

†Barrett, E.L.L.B., A. J. Moore and P. J. Moore. 2009. Diet and social conditions during sexual maturation have unpredictable influences on female life history trade-offs. Journal of Evolutionary Biology 22: 571-581.

Male reproductive strategies in Nauphoeta (selected publications):

‡Edvardsson, M., J. Hunt, A.J. Moore, and P.J. Moore. 2009. Quantitative genetic variation in the control of apoptosis under different environments.  Heredity 103: 217-222.

†Montrose, V.T., W.E. Harris‡, A.J. Moore and P.J. Moore. 2008. Investment in social status overrides investment in ejaculates as a response to both intrinsic differences and male condition.  Journal of Evolutionary Biology 21: 1290-1296.

‡Harris, W.E., A.J. Moore, and P.J. Moore. 2007. Variation in sperm size within and between ejaculates in a cockroach. Functional Ecology 21: 598-602.

‡Harris, W.E. and P.J. Moore. 2005. Females prefer males that have had fewer consorts.  American Naturalist 165: S64-S71.

Moore, A. J., P. A. Gowaty, W. Wallin, and P. J. Moore. 2001. Fitness costs of sexual conflict and the evolution of female mate choice and male dominance. Proceedings of the Royal Society of London B. 268: 517-523.

Nauphoeta cinerea females are ovoviviparous, giving birth to live young after brooding her eggs.

Social environment, reproduction, and development (selected publications):

Moore, P.J., W.E. Harris‡, and A.J. Moore. 2007. The cost of keeping eggs fresh: quantitative genetic variation in females that mate late relative to sexual maturation. American Naturalist 169: 311-322.

‡Harris, W.E. and P.J. Moore. 2005. Females prefer males that have had fewer consorts.  American Naturalist 165: S64-S71.

Moore, P.J. and W.E. Harris‡. 2003. Is a decline in offspring a necessary consequence of maternal age?  Proceedings of the Royal Society London B 270 (S2): 192-194.

Moore, P.J. and A.J. Moore. 2003.  Developmental flexibility and the effect of social environment on fertility and fecundity in parthenogenetic reproduction.  Evolution & Development 5: 163-168.

Moore, A.J., P. Gowaty, and P.J. Moore. 2003. Females avoid manipulative males and live longer.  Journal of Evolutionary Biology 16: 523-530.

Moore, P. J. and A. J. Moore. 2001. Reproductive ageing and mating: the ticking of the biological clock in female cockroaches.  Proceedings of the National Academy of Sciences USA 98: 9171-9176.

Moore, A. J., P. A. Gowaty, W. Wallin, and P. J. Moore. 2001. Fitness costs of sexual conflict and the evolution of female mate choice and male dominance. Proceedings of the Royal Society of London B. 268: 517-523.