For Researchers

Framing Challenges and Opportunities for Canada: Expert Panel on Regulating Gene-Edited Organisms for Pest Control

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CCA (Council of Canadian Academies),  Framing Challenges and Opportunities for Canada,  2023-11-21 11:21:00.
Gene-editing technologies are changing approaches to pest management. Rapidly evolving but unproven gene-editing tools could potentially mitigate the impacts of pests in public health, conservation, and agricultural contexts. The use of these tools, however, is accompanied by uncertainties about possible impacts on species and ecosystems, along with broader socioeconomic and cultural risks. Increased globalization and climate change are intensifying pest problems. These factors, combined with the waning effectiveness of many common pest-control tools, will contribute to growing pressure from both native and invasive pests if left unchecked. Opportunities to manage pests with greater effectiveness, lower costs, and increased safety therefore require consideration.

A toxin-antidote system contributes to interspecific reproductive isolation in rice

Shimin You, Zhigang Zhao, Xiaowen Yu, Shanshan Zhu, Jian Wang, Dekun Lei, Jiawu Zhou, Jing Li, Haiyuan Chen, Yanjia Xiao, Weiwei Chen, Qiming Wang, Jiayu Lu, Keyi Chen, Chunlei Zhou, Xin Zhang, Zhijun Cheng, Xiuping Guo, Yulong Ren, Xiaoming Zheng, Shijia,  Nature Communications,  14. 2023-11-18 09:43:22.
Breakdown of reproductive isolation facilitates flow of useful trait genes into crop plants from their wild relatives. Hybrid sterility, a major form of reproductive isolation exists between cultivated rice (Oryza sativa) and wild rice (O. meridionalis, Mer). Here, we report the cloning of qHMS1, a quantitative trait locus controlling hybrid male sterility between these two species. Like qHMS7, another locus we cloned previously, qHMS1 encodes a toxin-antidote system, but differs in the encoded proteins, their evolutionary origin, and action time point during pollen development. In plants heterozygous at qHMS1, ~ 50% of pollens carrying qHMS1-D (an allele from cultivated rice) are selectively killed. In plants heterozygous at both qHMS1 and qHMS7, ~ 75% pollens without co-presence of qHMS1-Mer and qHMS7-D are selectively killed, indicating that the antidotes function in a toxin-dependent manner. Our results indicate that different toxin-antidote systems provide stacked reproductive isolation for maintaining species identity and shed light on breakdown of hybrid male sterility.

Aedes aegypti microbiome composition covaries with the density of Wolbachia infection

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Jane Pascar, Henry Middleton & Steve Dorus,  Microbiome,  11. 2023-11-17 12:21:31.
Wolbachia is a widespread bacterial endosymbiont that can inhibit vector competency when stably transinfected into the mosquito, Aedes aegypti, a primary vector of the dengue virus (DENV) and other arboviruses. Although a complete mechanistic understanding of pathogen blocking is lacking, it is likely to involve host immunity induction and resource competition between Wolbachia and DENV, both of which may be impacted by microbiome composition. The potential impact of Wolbachia transinfection on host fitness is also of importance given the widespread release of mosquitos infected with the Drosophila melanogaster strain of Wolbachia (wMel) in wild populations. Here, population-level genomic data from Ae. aegypti was surveyed to establish the relationship between the density of wMel infection and the composition of the host microbiome.

Meiotic drive, postzygotic isolation, and the Snowball Effect

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Robert L. Unckless,  bioRxiv,  2023-11-14 12:43:39.
As populations diverge, they accumulate incompatibilities which reduce gene flow and facilitate the formation of new species. Simple models suggest that the genes that cause Dobzhansky-Muller incompatibilities should accumulate at least as fast as the square of the number of substitutions between taxa, the so-called snowball effect. We show, however, that in the special but possibly common case in which hybrid sterility is due primarily to cryptic meiotic (gametic) drive, the number of genes that cause postzygotic isolation may increase nearly linearly with the number of substitutions between species.

The suppression of a selfish genetic element increases a male’s mating success in a fly

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Sophie Lyth, Andrea J. Betancourt, Tom A. R. Price, Rudi L. Verspoor,  Ecology and Evolution,  2023-11-12 13:33:47.
X chromosome meiotic drive (XCMD) kills Y-bearing sperm during spermatogenesis, leading to the biased transmission of the selfish X chromosome. Despite this strong transmission, some natural XCMD systems remain at low and stable frequencies, rather than rapidly spreading through populations. The reason may be that male carriers can have reduced fitness, as they lose half of their sperm, only produce daughters, and may carry deleterious alleles associated with XCMD. Thus, females may benefit from avoiding mating with male carriers, yielding a further reduction in fitness. Genetic suppressors of XCMD, which block the killing of Y sperm and restore fair Mendelian inheritance, are also common and could prevent the spread of XCMD. However, whether suppressed males are as fit as a wild-type male remains an open question, as the effect that genetic suppressors may have on a male's mating success is rarely considered. Here, we investigate the mating ability of XCMD males and suppressed XCMD males in comparison to wild-type males in the fruit fly Drosophila subobscura, where drive remains at a stable frequency of 20% in wild populations where it occurs. We use both competitive and non-competitive mating trials to evaluate male mating success in this system. We found no evidence that unsuppressed XCMD males were discriminated against. Remarkably, however, their suppressed XCMD counterparts had a higher male mating success compared to wild-type controls. Unsuppressed XCMD males suffered 12% lower offspring production in comparison to wild-type males. This cost appears too weak to counter the transmission advantage of XCMD, and thus the factors preventing the spread of XCMD remain unclear.

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