| 1. |
- Chen, Wenbo, et al.
(author)
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The draft genome of whitefly Bemisia tabaci MEAM1, a global crop pest, provides novel insights into virus transmission, host adaptation, and insecticide resistance
- 2016
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In: BMC Biology. - : Springer Science and Business Media LLC. - 1741-7007. ; 14:1
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Journal article (peer-reviewed)abstract
- Background: The whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is among the 100 worst invasive species in the world. As one of the most important crop pests and virus vectors, B. tabaci causes substantial crop losses and poses a serious threat to global food security. Results: We report the 615-Mb high-quality genome sequence of B. tabaci Middle East-Asia Minor 1 (MEAM1), the first genome sequence in the Aleyrodidae family, which contains 15,664 protein-coding genes. The B. tabaci genome is highly divergent from other sequenced hemipteran genomes, sharing no detectable synteny. A number of known detoxification gene families, including cytochrome P450s and UDP-glucuronosyltransferases, are significantly expanded in B. tabaci. Other expanded gene families, including cathepsins, large clusters of tandemly duplicated B. tabaci-specific genes, and phosphatidylethanolamine-binding proteins (PEBPs), were found to be associated with virus acquisition and transmission and/or insecticide resistance, likely contributing to the global invasiveness and efficient virus transmission capacity of B. tabaci. The presence of 142 horizontally transferred genes from bacteria or fungi in the B. tabaci genome, including genes encoding hopanoid/sterol synthesis and xenobiotic detoxification enzymes that are not present in other insects, offers novel insights into the unique biological adaptations of this insect such as polyphagy and insecticide resistance. Interestingly, two adjacent bacterial pantothenate biosynthesis genes, panB and panC, have been co-transferred into B. tabaci and fused into a single gene that has acquired introns during its evolution. Conclusions: The B. tabaci genome contains numerous genetic novelties, including expansions in gene families associated with insecticide resistance, detoxification and virus transmission, as well as numerous horizontally transferred genes from bacteria and fungi. We believe these novelties likely have shaped B. tabaci as a highly invasive polyphagous crop pest and efficient vector of plant viruses. The genome serves as a reference for resolving the B. tabaci cryptic species complex, understanding fundamental biological novelties, and providing valuable genetic information to assist the development of novel strategies for controlling whiteflies and the viruses they transmit.
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| 2. |
- Mbiba, Monicah, et al.
(author)
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Social capital is subordinate to natural capital in buffering rural livelihoods from negative shocks : Insights from rural South Africa
- 2019
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In: Journal of Rural Studies. - : Elsevier. - 0743-0167 .- 1873-1392. ; 65, s. 12-21
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Journal article (peer-reviewed)abstract
- Rural livelihoods in developing countries are disproportionately vulnerable to multiple shocks and stresses that exacerbate vulnerability, which can result in increased dependence on natural resources. Several studies have been conducted on the safety net role of natural resources, which lower the impact of negative shocks on rural livelihoods. However, the role of social capital as a safety net that can potentially lower natural resource use when households experience negative shocks has been less studied. We examined the role of natural resources and social capital as buffers against negative shocks to reduce vulnerability in rural livelihoods. Using five years of panel data from a rural population in South Africa, multilevel models were constructed to quantify the influence of shocks, social capital and household socio-demographic characterization on three dimensions of natural resource use, namely the number of types of natural resources used, the frequency of natural resource use, and the quantities of natural resources used. Results show that household experience of negative shocks was consistently associated with a significant increase in all dimensions of natural resource use. However, and unexpectedly, social capital did not significantly reduce natural resource use when households experienced shocks. This in no way discounts the role social capital plays in cushioning households post experience of shocks, but rather indicates that reliance on social and natural capital could be complementary rather than substitutable coping strategies post experience of shocks. Efforts to secure rural livelihoods and achieve sustainability should thus focus on building household physical capital to reduce dependency on natural resources in rural households.
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