In aquatic ecosystems invasive species are among the most important threats to biodiversity worldwide. Understanding the dispersal mechanisms of aquatic invaders is very important for protection and management of vulnerable water bodies. Here we ask how recreational boats that are transported overland could contribute to the dispersal of invasive zebra mussels among lakes in Switzerland. Using a questionnaire sent to registered boat owners, we surveyed properties of transported boats and collected information on self-reported mussel fouling and transport activities of boat owners. We also sampled boat hulls at launching ramps and harbors for biofouling invertebrates. Boats that were kept seasonally or year-round in water were found to have high vector potential with mussel fouling rates of more than 40 %. However, only about 6 % of boats belonging to these groups were transported overland to other water bodies. Considering that approximately 100,000 recreational boats are registered in Switzerland, we estimated that every year around 1400 boats fouled with mussels are transported overland. Such boats pose a high risk of distributing zebra mussels between water bodies. Our results suggest that there is a considerable risk that recreational boats may spread new fouling species to all navigable water bodies within the study area. We speculate that one such species could be the quagga mussel, which has not yet invaded lakes in Switzerland. On a more positive note, our study has identified the group of high-risk boats so that possible control measures would only affect a relatively small number of boat owners.
We thank Prof. Ladd Johnson and three anonymous reviewers for the constructive comments on our manuscript and the Cantonal Waterways and Shipping Offices for helping us with sending our survey to a random sample of boat owners. Special thanks also go to Elisabeth Britt, Gabriela Etter, Sabrina Moerz, Jessica Lardon and Tiago Pereira for help with our field sampling campaign and to all boat owners who filled in the questionnaire. This work was financed by the Swiss Federal Office for the Environment (FOEN) and the Swiss Federal Institute for Environmental Sciences and Technology (Eawag). Data on the registered boats in Switzerland were provided by the Swiss Federal Statistical Office and data on densities of zebra mussel larvae and temperature in Lake Zrich was provided by Oliver Koester (Wasserversorgung, City of Zrich).
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This publication addresses the emergent issue in the Pacific Northwest of a potato infection called zebra chip disease, vectored by the potato psyllid. Includes information on the bacterium, the biology of the vector, description of damage from both vector and non-vector psyllids, and most current research on management.
Successful transmission of plant pathogens by insects depends on the vector inoculation efficiency and how rapidly the insect can effectively transmit the pathogen to the host plant. The potato psyllid, Bactericera cockerelli (Sulc), has recently been found to transmit "Candidatus Liberibacter solanacearum," a bacterium associated with zebra chip (ZC), an emerging and economically important disease of potato in several parts of the world. Currently, little is known about the epidemiology of ZC and its vector's inoculation capabilities. Studies were conducted in the field and laboratory to 1) assess transmission efficiency of potato psyllid nymphs and adults; 2) determine whether psyllid inoculation access period affects ZC incidence, severity, and potato yield; and 3) determine how fast the psyllid can transmit liberibacter to potato, leading to ZC development. Results showed that adult potato psyllids were highly efficient vectors of liberibacter that causes ZC and that nymphs were less efficient than adults at transmitting this bacterium. It was also determined that inoculation access period had little influence on overall ZC disease incidence, severity, and resulting yield loss. Moreover, results showed that exposure of a plant to 20 adult potato psyllids for a period as short as 1 h resulted in ZC symptom development. Furthermore, it was shown that a single adult potato psyllid was capable of inoculating liberibacter to potato within a period as short as 6 h, thereby inducing development of ZC. This information will help in developing effective management strategies for this serious potato disease.
Zebra finch is a representative animal model for studying the molecular basis of human disorders of vocal development and communication. Accordingly, various functional studies of zebra finch have knocked down or introduced foreign genes in vivo; however, their germline transmission efficiency is remarkably low. The primordial germ cell (PGC)-mediated method is preferred for avian transgenic studies; however, use of this method is restricted in zebra finch due to the lack of an efficient gene transfer method for the germline. To target primary germ cells that are difficult to transfect and manipulate, an adenovirus-mediated gene transfer system with high efficiency in a wide range of cell types may be useful. Here, we isolated and characterized two types of primary germline-competent stem cells, PGCs and spermatogonial stem cells (SSCs), from embryonic and adult reproductive tissues of zebra finch and demonstrated that genes were most efficiently transferred into these cells using an adenovirus-mediated system. This system was successfully used to generate gene-edited PGCs in vitro. These results are expected to improve transgenic zebra finch production.
Zebra finch (Taeniopygia guttata), a representative songbird, is a useful model animal for investigating the brain, behavioral, and neurobiological processes because it can learn vocalizations by imitating a singing adult, similar to humans who acquire spoken language. This trait is not observed in traditional model organisms such as rodents and non-human primates and is rarely found in other mammals1,2. In zebra finch, functional gene analyses have been performed by controlling gene expression via transient knockdown or overexpression of genes of interest in vivo3,4,5,6. Transgenic models that express the human mutant huntingtin gene or mutant forms of cAMP response element-binding protein have been developed by injecting lentiviruses containing transgenes into blastoderms of fertilized eggs to target primordial germ cells (PGCs). However, the low efficiency of this method indicates that improvements are required for studies of transgenic songbirds2,7,8.
Germline-competent stem cells, including PGCs and spermatogonial stem cells (SSCs), are animal cells that can transfer all genetic information to the next generation, self-renew, and differentiate into mature gametes. These characteristics make germline-competent stem cells a suitable resource for generating transgenic animals. PGCs, which give rise to sperm and oocytes, are the most actively studied germline-competent stem cells in avian species, especially chickens, and have become a very popular system for creating a variety of transgenics related to bioreactors and disease models9,10,11,12,13. SSCs, the other type of male germline-competent stem cells in adult testes that are precursors in spermatogenesis, have been successfully isolated from mammalian species, cultured, and used for transgenic production14,15. SSCs of several bird species including chickens, pheasants, and quails have been isolated and cultured, but practical applications for producing transgenic birds using these cells are limited16,17,18,19,20. In zebra finch, although studies have reported the isolation and manipulation of PGCs, reports of exogenous genes being efficiently delivered into these cells are limited21,22. Recently, transgenic zebra finches were generated using PGCs and lentiviral vectors, but the green fluorescent protein (GFP) transgene transferred by lentiviruses was lowly expressed and only detected using an anti-GFP antibody in sectioned tissues of transgenic finches22. Thus, further investigations of PGCs and SSCs are required to facilitate in vitro manipulation of these cells and obtain basic data in order to induce genome modifications in zebra finch germline-competent stem cells.
A reliable method to obtain germline-competent zebra finch cell lines has not been developed. In vivo transfection and gene transfer into primary cells are transgenic technologies that do not require established cell lines, but it is difficult to achieve high efficiency with these methods. Virus-mediated transduction may be an alternative for gene transfer into isolated primary germline-competent stem cells, which have low transfection rates using universal transfection methods such as lipofection. Viral vectors have been used to transfer genes into cells and living organisms. Adenoviruses are an important type of viral vector that have a relatively high transduction efficiency in target cells and infect a large range of host cells, including dividing and nondividing cells and several types of stem cells that are difficult to transfect23. Adenovirus-mediated gene transfer into mammalian germline stem cells has been successfully performed in vivo and in vitro23,24. Targeted gene disruption using adenovirally delivered Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 was also recently reported in birds25,26.
In this study, we describe an efficient method to transfer genes into primary germline-competent stem cells, including PGCs and SSCs, of zebra finch that overcomes the aforementioned limitations. We additionally induced a targeted genome modification in zebra finch PGCs using the established gene transfer method and CRISPR/Cas9 system. The biological functions of the genome-edited cells were verified by their incorporation into host reproductive tissues upon in vivo transplantation. These results could facilitate the production of transgenic and genetically modified zebra finches in future research. 0852c4b9a8
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