Sequencing and variant detection of eight abundant plant-infecting tobamoviruses across Southern California wastewater.

Abstract

Tobamoviruses are agriculturally-relevant viruses that cause crop losses and have infected plants in many regions of the world. These viruses are frequently found in municipal wastewater - likely coming from human diet and industrial waste across wastewater catchment areas. As part of a large wastewater-based epidemiology study across Southern California, we analyzed RNA sequence data from 275 influent wastewater samples obtained from eight wastewater treatment plants with a catchment area of approximately 16 million people from July 2020 - August 2021. We assembled 1,083 high-quality genomes, enumerated viral sequencing reads, and detected thousands of single nucleotide variants from eight common tobamoviruses: Bell Pepper Mottle Virus, Cucumber Green Mottle Mosaic Virus, Pepper Mild Mottle Virus, Tobacco Mild Green Mosaic Virus, Tomato Brown Rugose Fruit Virus, Tomato Mosaic Virus, Tomato Mottle Mosaic Virus, and Tropical Soda Apple Mosaic Virus. We show that single nucleotide variants had amino acid-altering consequences along with synonymous mutations, which represents potential evolution with functional consequences in genomes of these viruses. Our study shows the importance of wastewater sequencing to monitor the genomic diversity of these plant-infecting viruses, and we suggest that our data could be used to continue tracking the genomic variability of such pathogens. ImportanceDiseases caused by viruses in the genus Tobamovirus cause crop losses around the world. As with other viruses, mutation occurring in the virus genomes can have functional consequences and may alter viral infectivity. Many of these plant-infecting viruses have been found in wastewater, likely coming from human consumption of infected plants and produce. By sequencing RNA extracted from influent wastewater obtained from eight wastewater treatment plants in Southern California, we assembled high-quality viral genomes and detected thousands of single nucleotide variants from eight tobamoviruses. Our study shows that Tobamovirus genomes vary at many positions, which may have important consequences to viral host switching and the detection of these viruses by agricultural or environmental scientists.