Jalali Javaran, V. | bioRxiv Science

bioRxiv2023

From Asymptomatic to Symptomatic: Multiomics profiling of the temporal response of grapevine viral-mixed infection

Mixed viral infections are common in grapevines. However, our understanding of the factors and signaling pathways that influence the expression of viral symptoms in mixed infections is still incomplete. In a previous study, we revealed that the presence of grapevine leafroll-associated virus species in mixed infections was randomly associated with the devel-opment of virus-like symptoms. To understand what drives the timing of these virus-like symptoms in mixed infections, we used dsRNA and total RNA sequencing and metabolomic analysis to profile the viromes, metabolites, and transcripts of grapevine leaves collected at two different times of the year (summer and autumn). We demonstrated that neither viral titre nor virome composition changes were associated with symptom expression in autumn. The total phenolic content and antioxidant capacity increased in most plants except for those with early onset symptoms. According to the results of differential gene expression analysis, cell wall biosynthesis pathways were significantly downregulated in all grapevine plants infected with grapevine leafroll-associated virus 3, grapevine asteroid mosaic-associated virus, and grape-vine Pinot gris virus. In addition, polyketide pathways were significantly upregulated in all cultivars, while flavonoid precursor (e.g. abscisic acid) production was significantly reduced in plants that expressed strong virus-like symptoms. In the Vidal cultivar, an uncharacterized double-stranded RNA-binding protein (DRB) appears to play a critical role in the plants an-tiviral defences, supporting the recent hypothesis that DRBs make an important contribution to dominant antiviral responses in plants. The seasonality of the expression virus-like symptoms appears to be a consequence of the dynamic interactions between antiviral factors and viral counter-defences that occur at different developmental stages of grapevine.

plant biology↗

bioRxiv2022

Soil metatranscriptomics: An improved RNA extraction method toward functional analysis using nanopore direct RNA sequencing

Soil microbes play an undeniable role in sustainable agriculture, plant health, and soil management. A deeper understanding of soil microbial composition and function has been gained through next-generation sequencing. While soil metagenomics has provided valuable information about microbial diversity, issues stemming from RNA extraction, low RNA abundance in some microbial populations (e.g., viruses), and mRNA enrichment have slowed the progress of soil metatranscriptomics. A variety of soil RNA extraction methods have been developed so far. Yet none of the available protocols can obtain RNA with high quality, purity, and yield for third-generation sequencing. This latter requires RNA with high quality and large quantities (with no or low contamination, such as humic acids). Also, use of commercial kits for in-batch soil RNA extraction is quite expensive, and these commercial kits lack buffer composition details, which prevents the optimization of protocols for different soil types. An improved and cost-effective method for extracting RNAs from mineral and organic soils is presented in this paper. An acidic sodium acetate buffer and phosphate buffer with modifications to bead-beating and nucleic acid precipitation lead to higher RNA yields and quality. Using this method, we obtained almost DNA-free RNA. By using nanopores direct RNA sequencing, the extracted contamination-free RNAs were successfully sequenced. Lastly, taxonomic groups such as bacteria, fungi, archaea, and viruses were classified and profiled as well as functional annotation of the datasets was carried out using an in-house customized bioinformatics workflow.

microbiology↗