Browsing by Author "Christopher A. Omongo"

Now showing 1 - 3 of 3

Comparative evolutionary analyses of eight whitefly Bemisia tabaci sensu lato genomes: cryptic species, agricultural pests and plant-virus vectors
(BMC Genomics, 2023-07-19) Lahcen I. Campbell; Joachim Nwezeobi; Sharon L. van Brunschot; Tadeo Kaweesi; Susan E. Seal; Rekha A. R. Swamy; Annet Namuddu; Gareth L. Maslen; Habibu Mugerwa; Irina M. Armean; Leanne Haggerty; Fergal J. Martin; Osnat Malka; Diego Santos‐Garcia; Ksenia Juravel; Shai Morin; Michael E. Stephens; Paul Visendi Muhindira; Paul J. Kersey; M. N. Maruthi; Christopher A. Omongo; Jesús Navas‐Castillo; Elvira Fiallo‐Olivé; Ibrahim Umar Mohammed; Hua‐Ling Wang; Joseph Onyeka; Titus Alicai; John Colvin
Background The group of > 40 cryptic white y species called Bemisia tabaci sensu lato are amongst the world’s worst agricultural pests and plant‐virus vectors. Outbreaks of B. tabaci s.l. and the associated plant‐virus diseases continue to contribute to global food insecurity and social instability, particularly in sub‐Saharan Africa and Asia. Published B. tabaci s.l. genomes have limited use for studying African cassava B. tabaci SSA1 species, due to the high genetic divergences between them. Genomic annotations presented here were performed using the ‘Ensembl gene annotation system’, to ensure that comparative analyses and conclusions reflect biological differences, as opposed to arising from different methodologies underpinning transcript model identification. Results WepresentheresixnewB.tabacis.l.genomesfromAfricaandAsia,andtwore‐annotatedpreviously published genomes, to provide evolutionary insights into these globally distributed pests. Genome sizes ranged between 616—658 Mb and exhibited some of the highest coverage of transposable elements reported within Arthropoda. Many fewer total protein coding genes (PCG) were recovered compared to the previously published B. tabaci s.l. genomes and structural annotations generated via the uniform methodology strongly supported a repertoire of between 12.8—13.2 × 103 PCG. An integrative systematics approach incorporating phylogenomic analysis of nuclear and mitochondrial markers supported a monophyletic Aleyrodidae and the basal positioning of B. tabaci Uganda‐1 to the sub‐Saharan group of species. Reciprocal cross‐mating data and the co‐cladogenesis pattern of the primary obligate endosymbiont ‘Candidatus Portiera aleyrodidarum’ from 11 Bemisia genomes further supported the phylogenetic reconstruction to show that African cassava B. tabaci populations consist of just three biological species. We include comparative analyses of gene families related to detoxification, sugar metabolism, vector competency and evaluate the presence and function of horizontally transferred genes, essential for understanding the evolution and unique biology of constituent B. tabaci. s.l species. Conclusions These genomic resources have provided new and critical insights into the genetics underlying B. tabaci s.l. biology. They also provide a rich foundation for post‐genomic research, including the selection of candidate gene‐ targets for innovative white y and virus‐control strategies.
Endemism and Reemergence Potential of the Ipomovirus Sweet Potato Mild Mottle Virus (Family Potyviridae) in Eastern Africa: Half a Century of Mystery
(Phytobiomes Journal, 2022-11-29) Arthur K. Tugume; Deusdedith R. Mbanzibwa; Titus Alicai; Christopher A. Omongo; M. N. Maruthi
Viruses have the ability to frequently colonize new hosts and ecological niches because of their inherently high genetic and evolutionary plasticity. However, a virus may emerge and remain of no or less economic importance until changes in viral or environmental factors dictate its epidemiological status. An example is sweet potato mild mottle virus (SPMMV), which was first reported in the 1970s on sweetpotato in eastern Africa. SPMMV has remained endemic in the region and poorly understood, yet accounting for 60 to 95% of losses, especially in mixed infections. Unlike other sweetpotato viruses which have global incidences, SPMMV has never been confirmed outside eastern Africa. This implicates the region as its center of origin but does not fully account for SPMMV’s exclusive geographic delimitation to eastern Africa. Despite its importance, several mysteries and research gaps surround SPMMV, which decelerate efforts for effective virus disease management in sweetpotato. The aim of this review is to articulate research gaps, propose pivotal scientific directions, and stimulate knowledge generation for better management of virus diseases in sweetpotato. Vector-mediated transmission of SPMMV remains enigmatic. Here, we postulate testable hypotheses to explain SPMMV transmission. Comparisons between SPMMV and cassava brown streak ipomoviruses demonstrate epidemiological “hallmarks” for monitoring SPMMV. Evolutionary forces on SPMMV coupled with the virus’ broad host range imply a “silent build up” of more fit variants in a changing climate, and this could explode into a worse disease conundrum. These information gaps need urgent filling to ease future management of virus disease emergences in sweetpotato.
Spatio-temporal changes in endosymbiont diversity and composition in the African cassava white y, Bemisia tabaci SSA1
(Frontiers, 2022-11-18) Hajar El Hamss; M. N. Maruthi; Hadija M. Ally; Christopher A. Omongo; Hua-Ling Wang; Sharon van Brunschot; John Colvin; Hélène Delatte
Sap-sucking insects, including whiteflies, are amongst the most devastating and widely distributed organisms on the planet. They are often highly invasive and endosymbiont communities within these insects help them adapt to new or changing environments. Bemisia tabaci (Gennadius; Hemiptera: Aleyrodidae) white y species are vectors of more than 500 known plant- viruses and harbour highly diverse endosymbionts communities. To date, however, white y–endosymbiont interactions, community structure and their spatio-temporal changes are still poorly understood. In this study, we investigated the spatio-temporal changes in the composition and diversity of bacterial endosymbionts in the agricultural crop pest white y species, Bemisia tabaci sub-Saharan Africa 1-subgroup 1 and 2 (SSA1-SG1 and SSA1- SG2). 16S rRNA amplicon sequencing analysis was carried out to characterise endosymbiont compositionsin eld-collected SSA1 (SSA1-SG1 and SSA1- SG2) populations infesting cassava in Uganda in 1997 and 2017. We detected Portiera, Arsenophonus, Wolbachia, Hamiltonella and Hemipteriphilus, with Arsenophonus and Wolbachia infections being predominant. Hemipteriphilus and Hamiltonella frequencies were very low and were detected in seven and two samples, respectively. Bacterial diversity based on three independent parameters including Simpson index, number of haplotypes and Bray–Curtis dissimilarity matrix was significantly higher in 1997 than in 2017. This period also coincided with the advent of super-abundant cassava-white y populations on cassava crops in Uganda. We discuss how endosymbionts may influence the biology and behaviour of whiteflies leading to population explosions.