Insights of maize lethal necrotic disease: A major constraint to maize production in East Africa

Kiruwa, Fatma Hussein; Feyissa, Tileye; Ndakidemi, Patrick A.

doi:10.5897/ajmr2015.7534

Cited by 20 publications

(12 citation statements)

References 38 publications

(47 reference statements)

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“…Notably, there were viruses that were detected in some areas that had shown no disease incidence by visual observation. Symptoms caused by MLN viruses can also differ based on the age of the maize plant, the variety implicated, environmental factors, MCMV and SCMV virus strain, and various viruses may induce similar symptoms in the same plant (Kiruwa et al, 2016;Mezzalama, 2015;Wang et al, 2017). The study found that symptoms of the disease were seen in some cases during the study, even though there was no MCMV or SCMV.…”

Section: Figure 11 Mln Incidence On Commonly Grown Maize Varieties Over the Yearsmentioning

confidence: 84%

Status of maize lethal necrosis disease in seed production system in Kenya

Eunice

Miano

W.M

et al. 2021

Cogent Food & Agriculture

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Maize production in Kenya is now under threat from the devastating maize lethal necrosis (MLN) disease in the field. This study was conducted to assess status of MLN in maize seed production fields from both small-and large-scale producers in Kenya. The survey was conducted in five Agro-ecological Zones (AEZ)s in 13 counties in 2015, 2017, 2018, and 2019. Sampling for asymptomatic and non-symptomatic was done using standardized protocol. On-site maize chlorotic mottle virus (MCMV) testing was performed by immunostrips followed by laboratory qRT-PCR test. A total of 2,550 ha was surveyed with 21% having MLN disease and varying levels of severity. The MLN incidence and severity was not significantly different (P > 0.05) in the various Kenyan sampled agroecological zones, counties, maize varieties, and maize growth stages. Elevated MLN incidences and severities were observed in sub-humid AEZs comprising Embu, Uasin Gishu, Nakuru, and Elegeyo Marakwet counties that form the hotspots for MLN disease. The main MLN-causing viruses detected using q-RT-PCR were MCMV and sugarcane mosaic virus (SCMV). Out of the total samples analyzed using qRT-PCR, 38% were found to have MCMV, 14% with SCMV, and 18% with both MCMV and SCMV. From the 185 sample analyzed with immunostrip from 2017 to 2019, 29 (16%) were positive for MCMV. Phytosanitary programs should be included in seed legislation for legal adoption and strategies to control the spread of MLN disease should focus on high-risk hotspots agroecological zones and counties.

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Section: Figure 11 Mln Incidence On Commonly Grown Maize Varieties Over the Yearsmentioning

confidence: 84%

Status of maize lethal necrosis disease in seed production system in Kenya

Eunice

Miano

W.M

et al. 2021

Cogent Food & Agriculture

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“…Given the severe losses it has caused since 2011 in mixed infection with the potyvirus SCMV in East Africa [7, 63, 64], China [10, 65, 66] and Ecuador [13], and given the cost of screening seed worldwide to ensure absence of this seed-transmitted virus [63, 67, 68], MCMV is almost certainly the most economically important virus in the >76-member Tombusviridae family. Thus, it is imperative to understand the life cycle of MCMV, including translation, to identify molecular targets for genetic approaches to control this virus.…”

Section: Discussionmentioning

confidence: 99%

The RNA of maize chlorotic mottle virus - the essential virus in maize lethal necrosis disease - is translated via a panicum mosaic virus-like cap-independent translation element

Carino

Scheets

Miller

2020

Preprint

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Maize chlorotic mottle virus (MCMV) combines with a potyvirus in maize lethal necrosis disease (MLND), an emerging disease worldwide that often causes catastrophic yield loss. To inform resistance strategies, we characterized the translation initiation mechanism of MCMV. We report that, like other tombusvirids, MCMV RNA contains a cap-independent translation element (CITE) in its 3’ untranslated region (UTR). The MCMV 3’ CITE (MTE) was mapped to nucleotides 4164-4333 in the genomic RNA. SHAPE probing revealed that the MTE is a variant of the panicum mosaic virus-like 3’ CITE (PTE). Like the PTE, electrophoretic mobility shift assays (EMSAs) indicated that eukaryotic translation initiation factor 4E (eIF4E) binds the MTE despite the absence of a m7GpppN cap structure, which is normally required for eIF4E to bind RNA. The MTE interaction with eIF4E suggests eIF4E may be a soft target for engineered resistance to MCMV. Using a luciferase reporter system, mutagenesis to disrupt and restore base pairing revealed that the MTE interacts with the 5’ UTRs of both genomic RNA and the 3’-coterminal subgenomic RNA1 via long-distance kissing stem-loop base pairing to facilitate translation in wheat germ extract and in protoplasts. However, the MTE is a relatively weak stimulator of translation and has a weak, if any, pseudoknot, which is present in the most active PTEs. Most mutations designed to form a pseudoknot decreased translation activity. Mutations in the viral genome that reduced or restored translation prevented and restored virus replication, respectively, in maize protoplasts and in plants. We propose that MCMV, and some other positive strand RNA viruses, favors a weak translation element to allow highly efficient viral RNA synthesis.Author SummaryIn recent years, maize lethal necrosis disease has caused massive crop losses in East Africa and Ecuador. It has also emerged in East Asia. Maize chlorotic mottle virus (MCMV) infection is required for this disease. While some tolerant maize lines have been identified, there are no known resistance genes that confer full immunity to MCMV. In order to design better resistance strategies against MCMV, we focused on how the MCMV genome is translated, the first step of gene expression required for infection by all positive strand RNA viruses. We identified a structure (cap-independent translation element) in the 3’ untranslated region of the viral RNA genome that allows the virus to usurp a host translation initiation factor in a way that differs from host mRNA interactions with the translational machinery. This difference may guide engineering of – or breeding for – resistance to MCMV. Moreover, this work adds to the diversity of known eukaryotic translation initiation mechanisms, as it provides more information on mRNA structural features that permit noncanonical interaction with a translation factor. Finally, owing to the conflict between ribosomes translating and viral replicase copying viral RNA, we propose that MCMV has evolved a relatively weak translation element in order to permit highly efficient RNA synthesis, and that this replication-translation trade-off may apply to other positive strand RNA viruses.

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“…Given the severe losses it has caused since 2011 in mixed infection with the potyvirus SCMV in East Africa (7,63,64), China (10,65,66) and Ecuador (13), and given the cost of screening seed to ensure absence of this seed-transmitted virus (63,67,68), MCMV is almost certainly the most economically important virus in the >76-member Tombusviridae family (23).Thus, it is imperative to understand the life cycle of MCMV, including translation, to identify molecular targets for genetic approaches to control this virus. All tombusvirids that have been studied contain a 3' CITE (35,40,60,69,70), yet these are not predictable because the class of 3' CITE a tombusvirid possesses does not always correlate with phylogeny (35,52).…”

Section: Cap-independent Translation Of MCMV Rnamentioning

confidence: 99%

The RNA of Maize Chlorotic Mottle Virus, an Obligatory Component of Maize Lethal Necrosis Disease, Is Translated via a Variant Panicum Mosaic Virus-Like Cap-Independent Translation Element

Carino

Scheets

Miller

2020

J Virol

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Maize chlorotic mottle virus (MCMV) combines with a potyvirus in maize lethal necrosis disease (MLND), a serious emerging disease worldwide. To inform resistance strategies, we characterized the translation initiation mechanism of MCMV. We report that MCMV RNA contains a cap-independent translation element (CITE) in its 3′ untranslated region (UTR). The MCMV 3′ CITE (MTE) was mapped to nucleotides 4164-4333 in the genomic RNA. SHAPE probing revealed that the MTE is a distinct variant of the panicum mosaic virus-like 3′ CITE (PTE). Like the PTE, electrophoretic mobility shift assays (EMSAs) indicated that eukaryotic translation initiation factor 4E (eIF4E) binds the MTE despite the absence of a m7GpppN cap structure, which is normally required for eIF4E to bind RNA. Using a luciferase reporter system, mutagenesis to disrupt and restore base pairing revealed that the MTE interacts with the 5′ UTRs of both genomic RNA and subgenomic RNA1 via long-distance kissing stem-loop interaction to facilitate translation. The MTE stimulates a relatively low level of translation and has a weak, if any, pseudoknot, which is present in the most active PTEs, mainly because the MTE lacks the pyrimidine-rich tract that base pairs to a G-rich bulge to form the pseudoknot. However, most mutations designed to form a pseudoknot decreased translation activity. Mutations in the viral genome that reduced or restored translation prevented and restored virus replication, respectively, in maize protoplasts and in plants. In summary, the MTE differs from the canonical PTE but falls into a structurally related class of 3′ CITE. IMPORTANCE In the past decade, maize lethal necrosis disease has caused massive crop losses in East Africa. It has also emerged in China and parts of South America. Maize chlorotic mottle virus (MCMV) infection is required for this disease. While some tolerant maize lines have been identified, there are no known resistance genes that confer immunity to MCMV. In order to improve resistance strategies against MCMV, we focused on how the MCMV genome is translated, the first step of gene expression by all positive-strand RNA viruses. We identified a structure (cap-independent translation element) in the 3′ untranslated region of the viral RNA genome that allows the virus to usurp a host translation initiation factor, eIF4E, in a way that differs from host mRNA interactions with the translational machinery. This difference indicates eIF4E may be a soft target for engineering of – or breeding for – resistance to MCMV.

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Insights of maize lethal necrotic disease: A major constraint to maize production in East Africa

Abstract: Maize Lethal Necrotic Disease (MLND) is a new disease in East Africa

Cited by 20 publications

References 38 publications

Status of maize lethal necrosis disease in seed production system in Kenya

Status of maize lethal necrosis disease in seed production system in Kenya

The RNA of maize chlorotic mottle virus - the essential virus in maize lethal necrosis disease - is translated via a panicum mosaic virus-like cap-independent translation element

The RNA of Maize Chlorotic Mottle Virus, an Obligatory Component of Maize Lethal Necrosis Disease, Is Translated via a Variant Panicum Mosaic Virus-Like Cap-Independent Translation Element

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