Biology subjects

Taylor, N. J.

Publications and source records attributed to Taylor, N. J..

5 recordsLinked to original sources

bioRxiv2026

Creating resistance to the whitefly Bemisia tabaci in cassava through RNAi-mediated targeting of multiple insect metabolic processes

It is commonplace in East Africa for 100% of cassava fields to be infected with Cassava mosaic disease (CMD) and/or Cassava brown streak disease (CBSD), resulting in annual losses of more than US$1.25 billion and reduced food and economic security for farming households. The vector of both diseases is the African cassava species of the whitefly Bemisia tabaci. Since the late 1990s, there has been an unprecedented increase in whitefly populations, to the extent that they are referred to as "super-abundant". Research efforts since the late 1990s has focused mainly on developing plant resistance to the viral pathogens and paid scant attention to understanding the root causes of disease epidemics or the control of whitefly infestation. Here, we aimed at developing long-term whitefly-control solutions using an in-planta RNA interference (RNAi) approach. First, transcriptome analysis identified candidate genes that play key roles in whitefly biology: osmoregulation, sugar metabolism and transport, symbiosis with endosymbiotic bacteria and detoxification of phytotoxins. Then, fifteen RNAi inverted repeat constructs were produced, designed to target the candidate genes and 140 independent transgenic lines were generated in cassava variety NASE 13. Whole plant bioassays showed insecticidal activity of transgenic plants, reaching 58% lethality for adults within 7 days and 75-90% lethality of nymphs after 25 days, compared to control plants. Target genes were confirmed to be downregulated by up to 2.5-fold in adult whiteflies and nymphs. We used population dynamics modelling to predict the potential of the RNAi technology to control whiteflies under field conditions in East Africa.

bioengineering↗

bioRxiv2022

Mutations in DNA polymerase δ subunit 1 mediate CMD2-type resistance to Cassava Mosaic Geminiviruses

Cassava mosaic disease suppresses cassava yields across the tropics. The dominant CMD2 locus confers resistance to the cassava mosaic geminiviruses. It has been reported that CMD2-type landraces lose resistance after regeneration through de novo morphogenesis. As full genome bisulfite sequencing failed to uncover an epigenetic mechanism for loss of resistance, we performed whole genome sequencing and genetic variant analysis and fine-mapped the CMD2 locus to a 190 kilobase interval. Data suggest that CMD2-type resistance is caused by a nonsynonymous, single nucleotide polymorphism in DNA polymerase {delta} subunit 1 (MePOLD1) located within this region. Virus-induced gene silencing of MePOLD1 in a Cassava mosaic disease-susceptible cassava variety produced a recovery phenotype typical of CMD2-type resistance. Analysis of other CMD2-type cassava varieties identified additional resistance alleles within MePOLD1. MePOLD1 resistance alleles represent important genetic resources for resistance breeding or genome editing, and elucidating mechanisms of resistance to geminiviruses.

plant biology↗

bioRxiv2021

CRISPR-Cas9-mediated knockout of CYP79D1 and CYP79D2 in cassava attenuates toxic cyanogen production

Cassava (Manihot esculenta Crantz) is a starchy root crop that supports over a billion people in tropical and subtropical regions of the world. This staple, however, produces toxic cyanogenic compounds and requires processing for safe consumption. Excessive consumption of insufficiently processed cassava, in combination with protein-poor diets, can have neurodegenerative impacts. Reducing the cyanogen content by conventional breeding is problematic due to the heterozygous nature of the crop; recombination will generally disrupt a clonally propagated cultivars suite of desirable traits. To reduce cyanide levels in cassava, we used CRISPR-mediated mutagenesis to disrupt the cytochrome P450 genes CYP79D1 and CYP79D2 whose protein products catalyze the first step in cyanogenic glucoside biosynthesis. Knockout of both genes eliminated cyanide in leaves and storage roots of cassava accession 60444 and the West African, farmer-preferred cultivar TME 419. Although knockout of CYP79D2 alone resulted in significant reduction of cyanide, mutagenesis of CYP79D1 did not, indicating these paralogs have diverged in their function. Our work demonstrates cassava genome editing for food safety, reduced processing requirements, and environmental benefits that could be readily extended to other farmer-preferred cultivars.

plant biology↗

bioRxiv2020

Visualizing cassava bacterial blight at the molecular level using CRISPR-mediated homology-directed repair

Research on a few model, plant-pathogen systems has benefitted from years of tool and resource development. This is not the case for the vast majority of economically and nutritionally important plants, creating a crop improvement bottleneck. Cassava bacterial blight (CBB), caused by Xanthomonas axonopodis pv. manihotis (Xam), is an important disease in all regions where cassava (Manihot esculenta Crantz) is grown. Here we describe development of a tool for molecular-level visualization of CBB dynamics in vivo. Using CRISPR-mediated homology-directed repair (HDR), we generated plants containing scarless insertion of a GFP reporter at the CBB susceptibility (S) gene MeSWEET10a. Activation of MeSWEET10a-GFP by Xam was subsequently visualized at transcriptional and translational levels. Development of this tool was facilitated by a time-saving, adaptable strategy for identifying successful products of HDR, currently a limiting factor in plant research. This strategy has the potential to enable such research in other systems, improving the practicality of HDR-based experimentation.

plant biology↗

bioRxiv2017

Simultaneous CRISPR/Cas9-mediated editing of cassava eIF4E isoforms nCBP-1 and nCBP-2 confers elevated resistance to cassava brown streak disease

Cassava brown streak disease (CBSD) is a major constraint on cassava yields in East and Central Africa and threatens production in West Africa. CBSD is caused by two species of positive sense RNA viruses belonging to the family Potyviridae, genus Ipomovirus: Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV). Diseases caused by the family Potyviridae require the interaction of viral genome-linked protein (VPg) and host eukaryotic translation initiation factor 4E (eIF4E) isoforms. Cassava encodes five eIF4E proteins: eIF4E, eIF(iso)4E-1, eIF(iso)4E-2, novel cap-binding protein-1 (nCBP-1), and nCBP-2. Protein-protein interaction experiments consistently found that VPg proteins associate with cassava nCBPs. CRISPR/Cas9-mediated genome editing was employed to generate ncbp-1, ncbp-2, and ncbp-1/ncbp-2 mutants in cassava cultivar 60444. Challenge with CBSV showed that ncbp-1/ncbp-2 mutants displayed delayed and attenuated CBSD aerial symptoms, as well as reduced severity and incidence of storage root necrosis. Suppressed disease symptoms were correlated with reduced virus titer in storage roots relative to wild-type controls. Our results demonstrate the ability to modify multiple genes simultaneously in cassava to achieve tolerance to CBSD. Future studies will investigate the contribution of remaining eIF4E isoforms on CBSD and translate this knowledge into an optimized strategy for protecting cassava from disease.

plant biology↗