Biology subjects

Whisson, S. C.

Publications and source records attributed to Whisson, S. C..

4 recordsLinked to original sources

bioRxiv2025

Isolation and proteomic analysis of intracellular vesicles from the potato late blight pathogen Phytophthora infestans

The oomycete Phytophthora infestans, a filamentous plant pathogen belonging to the kingdom Stramenopila, is the causal agent of potato late blight resulting in annual crop losses amounting to billions of dollars worldwide. Key to the success of this pathogen are the effector proteins it secretes during infection, whose functions include breaching the plant cell wall and suppression/evasion of plant immune responses. Currently, little is known regarding the intracellular trafficking of effectors enroute to secretion. In this study, we developed a robust density gradient ultracentrifugation method to isolate intracellular vesicles from P. infestans and to separate diverse vesicle populations based on buoyancy for the purpose of identifying vesicle-associated proteins by mass spectrometry. Gene Ontology Enrichment Analysis of proteins identified in buoyant fractions revealed enrichment for membrane-associated proteins and proteins involved in vesicle trafficking. Buoyant fractions were also enriched in RXLR class effectors, carbohydrate-active enzymes, and secretory proteins possessing N-terminal signal peptides, all representing potential vesicle cargo. In addition, previously identified P. infestans extracellular vesicle markers were also present. Unravelling how effector proteins are trafficked for secretion during infection is a critical step in developing robust strategies for combating potato late blight disease; the proteomics dataset and method presented here are valuable resources from which potential biomarkers for P. infestans vesicles can be identified for future studies towards this end.

cell biology↗

bioRxiv2024

Proteolytic processing of both RXLR and EER motifs in oomycete effectors

Arg-any amino acid-Leu-Arg (RXLR) effectors are central oomycete virulence factors that target diverse host proteins and processes to suppress plant immunity. Relatively little is known about how they are processed post-translationally before delivery into host cells. Proteolytic cleavage at the RXLR motif was observed to occur prior to secretion in all Phytophthora infestans effectors tested, suggesting it is a general rule, and was observed to occur between the leucine and the second arginine. There was no cleavage of a naturally occurring second RXLR motif in a structured region of Pi21388/AvrBlb1, or one introduced at a similar position in effector Pi04314, in keeping with the motif being positionally constrained, potentially to disordered regions closely following the signal peptide. Remarkably, independent proteolytic cleavage of the Glu-Glu-Arg (EER) motif, often found immediately downstream of the RXLR, was also observed in diverse effectors, occurring immediately after the arginine. Expression of full-length effectors in host plant Nicotiana benthamiana revealed that, although secreted, they were poorly processed, suggesting that RXLR and EER cleavage does not occur in all eukaryotic cells. Our observations indicate that, whether possessing both RXLR and EER, or either motif alone, these effectors are likely proteolytically processed prior to secretion in all cases.

plant biology↗

bioRxiv2023

Comparative Transcriptome Profiling Provides Insights into the Growth Promotion Activity of Pseudomonas fluorescens strain SLU99 in Tomato and Potato Plants

The use of biocontrol agents with plant growth-promoting activity has emerged as an approach to support sustainable agriculture. During our field evaluation of potato plants treated with biocontrol rhizobacteria, four bacteria were associated with increased plant height. Using two important solanaceous crop plants, tomato and potato, we carried out a comparative analysis of the growth-promoting activity of the four bacterial strains: Pseudomonas fluorescens SLU99, Serratia plymuthica S412, S. rubidaea AV10, and S. rubidaea EV23. Greenhouse and in vitro experiments showed that P. fluorescens SLU99 promoted plant height, biomass accumulation, and yield of potato and tomato plants, while EV23 promoted growth in potato but not in tomato plants. SLU99 induced the expression of plant hormone-related genes in potato and tomato, especially those involved in maintaining homeostasis of auxin, cytokinin, gibberellic acid and ethylene. Our results reveal potential mechanisms underlying the growth promotion and biocontrol effects of these rhizobacteria and suggest which strains may be best deployed for sustainably improving crop yield.

plant biology↗

bioRxiv2021

Spray-induced gene silencing as a potential tool to control potato late blight disease

Phytophthora infestans causes late blight disease on potato and tomato and is currently controlled by resistant cultivars or intensive fungicide spraying. Here, we investigated an alternative means for late blight control by spraying potato leaves with double-stranded RNAs (dsRNA) that target P. infestans genes that are essential for infection. Through confocal microscopy, we show that the sporangia of P. infestans expressing Green Fluorescent Protein (GFP) can take up in vitro synthesized dsRNAs homologous to GFP directly from their surroundings, including leaves, which leads to the reduced relative expression of GFP. We further demonstrate the potential of spray induced gene silencing (SIGS) in controlling potato late blight disease by targeting developmentally important genes in P.infestans such as guanine-nucleotide binding (G) protein {beta}-subunit (PiGPB1), haustorial membrane protein (PiHmp1), cutinase (PiCut3), and endo-1,3(4)-{beta}-glucanase (PiEndo3). Our results demonstrate that SIGS can be potentially used to mitigate potato late blight; however, the degree of disease control is dependent on the selection of the target genes.

plant biology↗