Category Archives: Uncategorized

Read the new publication in Plants here!

A sudden, unexplained decline and collapse of young apple trees on dwarfing and semi-dwarfing rootstocks has been reported across North America over the past decade. Although viruses have been detected in declining trees, no information is available on their potential causal role in the decline phenomenon. To this end, virus-inoculated apple trees were established in a high-density experimental orchard and monitored over five years. Tree decline was observed in year 4 (2022), resulting in 17% mortality, with declining trees exhibiting marked vascular tissue necrosis. However, none of the eight viruses and one viroid detected in the experimental orchard was significantly more prevalent in declining trees. Extreme temperature fluctuations in January 2022, followed by a severe water deficit in summer 2022, were recorded at the experimental orchard. Similar but distinct observations were made in a nearby commercial orchard with foliar nutrient imbalances documented in trees exhibiting symptoms of rapid decline. Together, our findings suggest that viruses are not primarily responsible for the rapid decline phenomenon and highlight the need for future work to investigate the roles of tree physiology and water stress in tree decline, as well as the potential efficacy of horticultural mitigation practices.

Brandon Roy receives mentions for his outstanding paper titled: Predictive Modeling of Proteins Encoded by a Plant Virus Sheds a New
Light on Their Structure and Inherent Multifunctionality. Congratulations, Brandon!

https://www.mdpi.com/2218-273X/14/1/62

Read the new publication in Insects here!

Tortistilus and Spissistilus are two genera of cryptic treehoppers from the Ceresini tribe. S. festinus is a vector of grapevine red blotch virus (GRBV) in vineyards in northern California, USA; however, the transmission capabilities of Tortistilus spp. are unknown. In this study, we determined the species of Tortistilus found in vineyards in Napa Valley, California, as T. wickhami, and determined that only a few specimens but no dissected heads with salivary glands tested positive for GRBV in PCR and qPCR. These results suggested that T. wickhami is an unlikely vector of GRBV in northern California vineyards.

https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1451285/full

GFLV VSRs include the RNA1-encoded protein 1A and the putative helicase protein 1B^Hel, as well as their fused form (1AB^Hel). Key characteristics underlying the suppression function of the GFLV VSRs are unknown. In this study, we explored the role of the conserved tryptophan-glycine (WG) motif in protein 1A and glycine-tryptophan (GW) motif in protein 1B^Hel in their systemic RNA silencing suppression ability by co-infiltrating Nicotiana benthamiana 16c line plants with a GFP silencing construct and a wildtype or a mutant GFLV VSR. We analyzed and compared wildtype and mutant GFLV VSRs for their (i) efficiency at suppressing RNA silencing, (ii) ability to limit siRNA accumulation, (iii) modulation of the expression of six host genes involved in RNA silencing, (iv) impact on virus infectivity in planta, and (v) variations in predicted protein structures using molecular and biochemical assays, as well as bioinformatics tools such as AlphaFold2.

Read the new publication in the American Journal of Enology and Viticulture here!

Background and goals Grapevine red blotch virus (GRBV) causes red blotch disease and is a threat to vineyard sustainability in some areas. Advances in disease epidemiology have been made, but information on the latency period of GRBV is lacking. This work aimed to estimate red blotch disease latency (the time between a vine first testing positive for GRBV and the onset of disease symptoms).

Methods and key findings Sentinel vines consisting of GRBV-negative Cabernet franc buds grafted onto GRBV-negative 3309 Couderc cuttings were planted in June 2015 in a red blotch-diseased Cabernet franc vineyard experiencing secondary spread of GRBV. Sentinel vines were monitored for disease symptoms from October 2015 to 2023, and were sampled annually for GRBV testing from October 2015 to 2023 and from June 2021 to 2022. The first sentinel vine tested positive for GRBV by polymerase chain reaction (PCR) in October 2018; this vine became symptomatic the following October. An increasing number of sentinel vines tested positive for GRBV by PCR and exhibited foliar disease symptoms either when the virus was detected, or four to 12 months later.

Conclusions and significance Of those sentinel vines that became infected (69%, 25/36), three distinct patterns of initial GRBV detection and disease symptom onset were observed. The first applied to sentinel vines (20%, 5/25) that were both GRBV positive by PCR and symptomatic for the first time in October. The second pattern applied to sentinel vines (56%, 14/25) that were GRBV positive by PCR for the first time in June and symptomatic the following October. The third pattern applied to sentinel vines (24%, 6/25) that were GRBV positive in PCR for the first time in October and not symptomatic until the following October. Estimating a four-to-12-month latency period enables a better understanding of red blotch disease trajectories in vineyards showing signs of secondary spread.

Congratulations to Jess on defending your thesis. Your extraordinary scientific discoveries during your PhD have transformed our understanding of viral suppressors of RNA silencing encoded by GFLV. We cannot wait to see what you contribute to plant virology next!

https://bmcmicrobiol.biomedcentral.com/articles/10.1186/s12866-024-03399-x#citeas

The study includes phenotyping infected Nicotiana benthamiana plants through excavation and machine learning assisted mapping of root traits. The modifications were correlated with the production of reactive oxygen species in the root vasculature, suggesting a strong immune response in some viral isolates, but less so in other viral isolates. Further transcriptomic profiling of the root tissue revealed that dysregulation of immune response genes, pattern recognition receptors, and signaling pathways were correlated with viral infection and symptoms in roots. This study represents a new avenue for research in GFLV, as root biology for the nematode-vectored Nepovirus have not been explored.

Congratulations to Jess Choi for receiving the 2024 Gilmer Award, given in celebration and memory of Robert M. Gilmer!

Jess Choi receives honorable mentions for her paper titled: Grapevine fanleaf virus RNA1-encoded proteins 1A and 1B ^Hel  suppress RNA silencing. Congratulations, Jess!

Lab members Brandon Roy and Jess Choi work together to publish a paper revolved around the molecular mechanics of grapevine fanleaf virus, a serious threat to grapevine production worldwide. With the advent of new software for protein prediction, they leveraged the capacity of protein modeling on the entire GFLV genome to analyze and postulate functions of each protein. Two strains with the most currently available published data, ‘GHu’ and ‘F13’, were parsed for protein encoding regions and analyzed for three-dimensional confirmation models. The models produced from over 20 programs ranged in confidence and they identified two algorithms to be the most confident; AlphaFold2 and D-I-TASSER. These models, along with other confirmatory analyses confirmed eight previously known molecular functions of GFLV proteins, and predicted several additional functions across the entire genome and satellite RNA molecule. This work represents an updated understanding of the GFLV genome and strategically points to future directions in elucidating the molecular biology of GFLV.

Biomolecules: 14(1), 62