The Interspecific Fungal Hybrid Verticillium longisporum Displays Subgenome-Specific Gene Expression

Verticillium is a genus of plant-associated fungi that includes a few plant pathogens that collectively affect a wide range of hosts. On several occasions, haploid Verticillium species hybridized into the stable allodiploid species Verticillium longisporum , which is, in contrast to haploid Verticillium species, a Brassicaceae specialist.

In-depth evaluation of root infection systems using the vascular fungus Verticillium longisporum as soil-borne model pathogen

Background While leaves are far more accessible for analysing plant defences, roots are hidden in the soil, leading to difficulties in studying soil-borne interactions. Inoculation strategies for infecting model plants with model root pathogens are described in the literature, but it remains demanding to obtain a methodological overview. To address this challenge, this study uses the model root pathogen Verticillium longisporum on Arabidopsis thaliana host plants and provides recommendations for selecting appropriate infection systems to investigate how plants cope with root pathogens. Results A novel root infection system is introduced, while two existing ones are precisely described and optimized. Step-by-step protocols are presented and accompanied by pathogenicity tests, transcriptional analyses of indole-glucosinolate marker genes and independent confirmations using reporter constructs. Advantages and disadvantages of each infection system are assessed. Overall, the results validate the importance of indole-glucosinolates as secondary metabolites that limit the Verticillium propagation in its host plant. Conclusion Detailed assistances on studying host defence strategies and responses against V. longisporum is provided. Furthermore, other soil-borne microorganisms (e.g., V. dahliae) or model plants, such as economically important oilseed rape and tomato, can be introduced in the infection systems described. Hence, these proven manuals can support finding a root infection system for your specific research questions to further decipher root-microbe interactions.

In-depth evaluation of root infection systems with the vascular fungus Verticillium longisporum as soil-borne model pathogen

ABSTRACTPREMISEWhile leaves are far more accessible for analysing plant defences, roots are hidden in the soil leading to difficulties in studying soil-borne interactions. Literature describes inoculation strategies to infect model plants with model root pathogens, but it remains demanding to obtain a methodological overview. To address this challenge, this study uses the model root pathogen Verticillium longisporum on Arabidopsis thaliana and provides recommendations based on evident examples for the selection and management of suitable infection systems to investigate root-microbe interactions.METHODS AND RESULTSA novel root infection system is introduced, while two existing ones are precisely described and optimized. Advantages and disadvantages of each are assessed, step-by-step protocols are presented and accompanied by pathogenicity tests, transcriptional analyses of indole-glucosinolate markers and independent confirmations using reporter constructs. The results validate the importance of indole-glucosinolates as secondary metabolites limiting V. longisporum propagation in hosts.DISCUSSIONWe provide detailed guidelines for studying host responses and defence strategies against V. longisporum. Furthermore, other soil-borne microorganisms or other model plants, such as economically important oilseed rape, can be used in the infection systems described. Hence, these proven manuals help to find a root infection system for your specific research questions to decipher root-microbe interactions.

Structural Characterization of Novel Luciferase from Bioluminescence Fungi Verticillium longisporum

Luciferase is an enzyme that catalyses a reaction to produce a visible light using an oxidative process, a chemical reaction that is typically referred to as bioluminescent. Insects, bacterial origin or microorganism of marine nature were considered as the mainly sources of discovered luciferase. The protein was commercialized for biomedical and biotechnological use as reporter gene. The first discovered wild form of luciferase originally from Photinu spyralis (firefly). Hence, there is need for both exploration and examination of novel luciferase to be expanded to new sources such as fungal which may likely be exploited to serve commercial purposes and applications. In this study, a novel uncharacterized luciferase protein from a fungal species Verticillium longisporum, was modelled and analysed using bioinformatic tools. The modelled 3D structure is of high quality with a PROCHECK score of 99.5%, ERRAT2 value of 91.01%, and Verify3D score of91.01%, showing that the conformational structure is acceptable. The result showed that the fungal luciferase enzyme share major characteristics with luciferase representative from various fungal and bacterial species. There is only a slight difference in the two nucleotide bindings in V. longisporum with a D/E substitution of D with E and S/T substitution. The difference of the two nucleotides binding from the two proteins may be related to the evolutionary trends. Other differences include increased number of hydrophobic and polar amino acid groups than aromatic and aliphatic ones, as well as more coils and loops with less strands. The distance between the ligand and the binding site that houses Asp 64 and Thr 110 from template proteins (Riboflavin lyaseRcaE) and Asp 543 and Thr 589 from model luciferase is similar. The only difference occurred in the V. longisporum; protein oxidoreductase activities acts on paired donors, incorporate or reduce molecular oxygen, while in the template protein oxidoreductase activities act on single donors with incorporation of molecular oxygen. This study on fungal sourced luciferase present a unique opportunity away from the more well established bacterial and insect based luciferase.

The Diurnal Rhythm of Brassica napus L. Influences Contents of Sulfur-Containing Defense Compounds and Occurrence of Vascular Occlusions during an Infection with Verticillium longisporum

Reduction in atmospheric sulfur and intensified agriculture have led to sulfur deficiency, often correlated with a higher susceptibility to pathogens. The spread of fungal pathogens, such as the soil-born Verticillium longisporum, was observed. Defense responses of infected plants are linked to sulfur-containing compounds including glucosinolates (GSLs). Some pathogens infect their hosts at specific time periods during the day. To investigate the relation of sulfur-containing metabolites with diurnal effects of infection time points, Brassica napus plants cultivated at two different sulfur supplies, were infected with V. longisporum at four different time points during the day. It was demonstrated that 3, 7 and 14 days after inoculation the infected plants differed in their infection rate depending on the time point of infection. Additionally, infected plants had higher contents of sulfur-containing metabolites, such as specific GSLs, in comparison to non-infected plants. Sufficient sulfur fertilization was always reflected in higher contents of sulfur-containing compounds as well as a lower rate of infection compared to sulfur-deprived plants. On the microscopic level vascular occlusions in the hypocotyl were visible and the amount was dependent on the time point of infection. The results might be used to optimize sulfur fertilization to reduce susceptibility to V. longisporum.

Identification and Characterization of Verticillium longisporum Lineage A1/D1 from Brassica Crops in Manitoba, Canada

Verticillium stripe in canola (Brassica napus L.) caused by Verticillium longisporum was first reported in Manitoba in 2014. In this study, Brassica crops including canola, mustard (Brassica juncea) and radish (Raphanus sativus) with visible symptoms of Verticillium stripe were collected from Portage La Prairie, Manitoba, and the pathogens were isolated. Isolates from canola and radish were identified to V. longisporum, which produced longer conidia (7.92–12.00 µm) than Verticillium dahliae (4.32–7.04 µm). An isolate derived from mustard was characterized as V. dahliae. Molecular diagnostics with 18S rDNA, 5.8S rDNA and mating-type marker primers were used to confirm the identification of Verticillium isolates. PCR-RFLP of the mitochondrial small subunit rDNA and the cytochrome b gene were also employed to distinguish V. longisporum isolates from V. dahliae. The multi-gene characterization approach allowed for lineage determination, and V. longisporum isolates from canola and radish were in the A1/D1 group. Isolates of Verticillium longisporum from canola inoculated onto the canola cultivar ‘Westar’ caused symptoms of stem striping, stunting and short plants. Re-isolated fungal strains from infected stems were again inoculated onto canola plants, in order to confirm that V. longisporum was the causal agent of Verticillium stripe disease in the pathogenicity test.