Biology subjects

Runo, S.

Publications and source records attributed to Runo, S..

3 recordsLinked to original sources

bioRxiv2022

A transcriptome atlas of Striga hermonthica germination

Societal Impact StatementWitchweeds, parasitic plants of the genus Striga, are nicknamed "cereal killers" because of their devasting destruction of Africas most staple cereals, including maize, sorghum, millets, and upland rice. The parasite relies on biomolecules emitted from the host roots to germinate and therefore initiate its infectious lifecycle. Some sorghum varieties have evolved to not produce effective germination stimulants, making them resistant to the parasite. Here, we assess genetic factors that underpin Striga germination. We discuss how such knowledge can be used to develop new Striga management strategies through the disruption of host-parasite communication exchange. SummaryO_LISeeds of the parasitic plant Striga are dormant. They only germinate in response to biomolecules emitted from the hosts root exudate, strigolactones (SL). But, it is now emerging that Striga germination is a much more complex process regulated by crosstalk of hormone signaling pathways. C_LIO_LITo further understand the genetic basis of the communication exchange between Striga and its host sorghum, we performed a comparative transcriptomic analysis. We sought to identify major transcriptomic changes that define the germination process in Striga and a set of genes that may contribute to the differences in germination rates. C_LIO_LIResults showed that germination proceeds immediately after SL perception and is marked by a wave of transcriptional reprogramming to allow for metabolic processes of energy mobilization. Cluster analysis using self-organizing maps (SOMs) revealed a time-phased and genotype-differentiated response to germination stimulation. The variation in germination was also a function of hormonal crosstalk. The early germination stage was associated with significant repression of genes in the abscisic acid (ABA) biosynthesis pathway. Other hormones influenced germination as follows: (i) ABA and auxin repressed germination, (ii) brassinosteroid, ethylene and jasmonic acid promoted germination, and (iii) cytokinin had a more prominent role post-germination rather than during germination. Perception of SL sets the germination programme leading to different rates of germination in sorghum followed by a complex hormonal regulation network that acts to either repress or enhance germination. These results have far-reaching implications for developing Striga management strategies by disrupting hormonal communication exchange. C_LI

plant biology↗

bioRxiv2022

Resolving intergenotypic Striga resistance in sorghum

Genetic underpinnings of host-pathogen interactions in the parasitic plant Striga hermonthica,a root parasitic plant that ravages cereals in sub-Saharan Africa, are unclear. We performed a comparative transcriptome study on five genotypes of sorghum exhibiting diverse resistance responses to S. hermonthica using weighted gene co-expression network analysis (WGCNA). We found that S. hermonthica elicits both basal and effector-triggered immunity - like a bona fide pathogen. Resistance response was genotype-specific. Some resistance responses followed the salicylic acid-dependent signaling pathway for systemic acquired resistance characterized by cell wall reinforcements, lignification and callose deposition while in others the WRKY-dependent signaling pathway was activated leading to a hypersensitive response (HR). In some genotypes, both modes of resistance were activated while in others, either mode dominated the resistance response. Cell-wall-based resistance was common to all sorghum genotypes but strongest in IS2814, while HR-based response was specific to N13, IS9830 and IS41724. WGCNA further allowed for pinpointing of S. hermonthica resistance causative genes in sorghum. Some highlights include a Glucan synthase-like 10, a pathogenesis-related thaumatin-like family, and a phosphoinositide phosphatase gene. Such candidate genes will form a good basis for subsequent functional validation and possibly future resistance breeding. HighlightParasitic plants of the Striga genus are major pests to cereals in Africa. We pinpointed genetic causes of Striga resistance in sorghum that can be harnessed for future resistance breeding.

plant biology↗

bioRxiv2020

Physiological and ecological warnings that Dodder pose an exigent threat to farmlands in Eastern Africa

Invasive holoparasitic plants of the genus Cuscuta (dodder) threaten Africas ecosystems, due to their rapid spread and attack on various host plant species. Most Cuscuta species cannot photosynthesize, hence rely on host plants for nourishment. After attachment through a peg-like organ called a haustorium, the parasites deprive hosts of water and nutrients leading to their death. Despite their rapid spread in Africa, dodders have attracted limited research attention, although data on their taxonomy, host range and epidemiology are critical for their management. Here, we combine taxonomy and phylogenetics to reveal presence of field dodder (Cuscuta campestris) and C. kilimanjari (both either naturalized or endemic to East Africa), and for the first time in continental Africa, presence of the giant dodder (C. reflexa) a south Asian species. These parasites have a wide host range, parasitizing species across 13 angiosperm orders. Evaluating the possibility of C. reflexa to expand this host range to tea, coffee, and mango, crops of economic importance to Africa, revealed successful parasitism, following haustorial formation and vascular bundle connections in all three crops. However, only mango mounted a successful post-attachment resistance response. Furthermore, species distribution models predicted high habitat suitability for all three Cuscuta species across major tea- and coffee-growing regions of Eastern Africa, suggesting an imminent risk to these crops. Our findings provide relevant insights into a little-understood threat to biodiversity and economic wellbeing in Eastern Africa, and providing critical information to guide development of management strategies to avert their spread. Sentence SummaryMicroscopy and habitat suitability modeling provide an early warning that dodders invasion in Eastern Africa poses a threat to important cash crops

ecology↗