The fourth edition of our series “What’s new in plant science?”, provides an overview on key scientific publications in September-December 2024. While not released by VIRTIGATION partners themselves, they still include crucial findings for the stakeholders of our multi-actor network.
New papers unveil surprising intricacies in plant viruses
Two new publications made strides in better unveiling the surprising intricacies of various plant viruses. A group of Spanish researchers investigated the prevalence and impact of mixed viral infections in cucurbit crops, specifically melon and watermelon, in Spain over three seasons from 2021 to 2023. Their study found that Cucurbit aphid-borne yellows virus (CABYV) was the most prevalent virus, followed by significant occurrences of watermelon mosaic virus (WMV). They also identified a novel polerovirus, Pepo aphid-borne yellows virus (PABYV). This virus had been present since 2018 but went unnoticed due to its similar symptoms to CABYV. This information is crucial for growers in particular, as it helps them understand which viruses are most likely to affect their crops.
Another Spanish research team explored how habitat heterogeneity in plant communities affects the ecology of plant-virus diseases. Host plants provide critical resources for viruses, and the spatial structuring of plant communities affects the niches available for virus colonization and disease emergence. Most viruses exhibit habitat specificity, with communities connected by key generalist viruses and potential host reservoirs. Their study found a significant association between habitat heterogeneity and virus community structuring, which is linked to virus resource utilization traits such as transmission mode and host range. This relationship is scale-dependent, being stronger at finer (site) scales than larger (habitat) scales. Habitat heterogeneity plays a role in plant virus community assembly, and virus community structuring corresponds to virus trait responses that vary with the scale of observation. These insights can help the value chain in improving disease forecasting, and also allow growers to better anticipate and mitigate potential virus outbreaks.
Leveraging genome editing to enhance crop resilience
Two recent papers by Chinese scientist teams highlighted the growing potential of genome editing technologies to enhance horticultural crop resilience. The first study investigated the role of eIF4E proteins in watermelon disease resistance, with a particular focus on the CleIF4E1 gene. By using CRISPR/Cas9 technology, they knocked out the CleIF4E1 gene, resulting in a mutant line that showed resistance to the zucchini yellow mosaic virus (ZYMV), though not to the cucumber green mottle mosaic virus (CGMMV). This study provides preliminary insights into the functions of eIF4E proteins in watermelon and suggests that tissue-specific editing of CleIF4E1 may help prevent adverse changes to watermelon fertility. This knowledge can aid in developing watermelon cultivars that are resistant to viral infections, thereby reducing crop losses. It could therefore guide future research and breeding programs aimed at enhancing viral resistance in watermelon.
The second Chinese study reviewed the development of broad-spectrum resistance (BSR) in crops to combat plant diseases caused by various pathogens. BSR is crucial for controlling crop diseases, improving yield and quality, and ensuring global food security. They summarized recent advances in understanding the plant immune system and its role in disease resistance, examining the molecular mechanisms underlying BSR in crops. Their review highlighted the use of novel genetic engineering and genome editing tools to study and engineer BSR genes in crops. The authors discussed various strategies to achieve BSR, including gene stacking, multiplexed genome editing, editing cis-regulatory elements, RNA interference, saturation mutagenesis, and precise genomic insertions. These insights could especially help plant breeders in adopting these advanced breeding techniques to develop new disease-resistant cultivars.
Recent advances in antiviral RNA interference
In two recently published papers, international research teams made significant advances in better leveraging the potential of antiviral RNA interference. The first study involving VIRTIGATION researchers Cécile Desbiez (INRAE) and Juan-José Lopez-Moya (CRAG) explored the phenomenon of transcriptional slippage in RNA viruses, a strategy that allows these viruses to maximize the coding information within their compact genomes. Transcriptional slippage is characterized by the appearance of insertions or deletions (indels) in nascent viral RNAs, leading to changes in the open reading frame (ORF). This can result in the production of alternative proteins or truncated products. Understanding the way how RNA viruses use transcriptional slippage to evolve could help the value chain to develop better strategies to manage viral diseases in crops.
In the second study, Chinese researchers investigated the role of antiviral RNA interference (RNAi) in inhibiting the seed transmission of cucumber mosaic virus (CMV) in its natural host, Arabidopsis thaliana. The study demonstrated that antiviral RNAi confers significant resistance to seed infection by CMV, showing higher potency compared to the inhibition of systemic infection in whole plants. Overall, this underscores the importance of antiviral RNAi in preventing seed transmission of CMV, which is crucial for controlling the spread of plant viruses and preventing disease epidemics in horticultural crops.
Unravelling insecticide resistance in the Bemisia tabaci
A new Malaysian review paper used omics approaches to explore the mechanisms behind insecticide resistance in the Bemisia tabaci whitefly. The Bemisia tabaci whitefly has developed resistance to insecticides due to prolonged exposure, regulated at the molecular level. The review discussed the use of genomics, transcriptomics, proteomics, and metabolomics to understand the Bemisia tabaci’s insecticide resistance mechanisms. The authors also note in this context that future techniques like RNA interference (RNAi) and CRISPR-Cas9 could be used to target and knock down detoxifying genes and enzymes, potentially providing new solutions to manage Bemisia tabaci infestations. Ultimately, using an integrated omics approach could help discover novel resistance mechanisms in the Bemisia tabaci including target site resistance and inhibitors. Additionally, the identification of key genes and enzymes involved in resistance can lead to more targeted interventions against this devastating plant pest, such as through gene silencing techniques.
The implications of pesticide immunotoxicity on insects
Finally, a recent review paper by an international research team delved into the nuanced impacts of sublethal pesticide exposure on the immune systems of both target and non-target insect species. It reveals how pesticides can interfere with neuroendocrine-linked, cellular, and humoral functions, increasing insect susceptibility to pathogens and parasites. These chemicals can either weaken or fortify insect immune responses, potentially leading to fitness costs. The authors also highlighted the need for more research into the secondary modes of action of pesticides, such as their impact on RNA interference (RNAi) pathways in beneficial insects like pollinators and natural pest predators. Understanding the immunomodulatory effects of pesticides is therefore crucial for integrated pest management (IPM) programs, and could help growers in choosing plant protection products that minimise harm to beneficial insects in their greenhouses.
