How do light and temperature affect lifecycle, development and pathogenicity in Verticillium?

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The project seeks to understand how the fungal pathogen Verticillium dahliae (Vd) responds to environmental signals such as light and temperature using knowledge gained through study of the model fungus Neurospora crassa. The molecular components that have been described as playing a central role in the circadian clock in Nc appear to be key to light and temperature signalling in Vd. The combination of RNAseq in fluctuating environmental conditions over time in wild type and mutant backgrounds along with bioinformatic prediction of co-regulated gene sets with common promoter motifs, will be used to generate hypotheses about the regulatory pathways controlling conidiation and microsclerotial production in response to light and temperature. Genetic analysis by single and double knockouts and promoter binding assays will lead to elucidation of these regulatory networks in Vd.
Following this, pathogenicity screens with mutants, confocal microscopy and gene expression profiling of plant-specific stages of fungal growth (using cell sorting) will be used to assess the role of 'clock' components in infection and development within plants, leading to a greater understanding of how the fungus responds to the environment in the roots and xylem. Using a hairpin WC-1 construct transformed into strawberry and raspberry we will test whether inhibition of condidial and microsclerotial production is possible using host-induced gene silencing. In order to assess the role of the clock in planta and to understand the regulatory changes that have led to the apparent loss of clock-like behaviour in Vd, promoter and gene swap experiments will be carried out and LUC-PEST constructs will be used to read the status of rhythmic oscillations. Taken together this will lead to novel information that could be used as the basis for novel disease control through disruption of environmentally modulated developmental transitions important for pathogenicity.

While this work is of a fundamental nature, there are several routes to achieving impact. In the UK alone the UK strawberry industry is worth £1bn per annum (up from £500m in 2012) and the raspberry market around £150M. Large amounts of production have moved out of soil and into expensive and sometimes hard to source substrates. In many regions there is a desire to return to the soil as costs are lower. The primary problem in soil-borne production is Verticillium, which in the UK is also a problem on potatoes and globally on lettuce, hops and tomato. In time, this is a potential area in which this research could have a meaningful impact.

Direct beneficiaries:
Chemical and biocontrol companies- developing new inhibitors of light/environmental sensing pathways. Just as chemical disruption of mating has been successful in insect pests, it could be possible to disrupt the lifecycle of soil borne pathogens, by disrupting responses to light and temperature. This may lead to the development of new control strategies, based upon the findings from this research .

Breeding companies- the use of HIGS against core fungal developmental genes
Many studies have now shown that trans-kingdom RNAi-mediated gene silencing is possible. The trialling of HIGS in two important soft fruit crops is important, not only for the control of Verticillium, but also as a tool in its own right .

Indirect beneficiaries
Growers and farmers- The likely complete withdrawal of the main soil fumigant in the UK could ultimately lead to annual crop losses between £60-125M with the existing, susceptible varieties if chloropicrin is not re-approved. This could be avoided if resistant varieties are developed and even if chloropicrin remains available in the short term, the fumigation costs of £4,000 per hectare could be saved, representing a national saving of c. £10M.

Government, public and policy benefits

Food security- Novel, technology-driven approaches to addressing agricultural problems are a key component in the drive to improve food security and self sufficiency. Research at this level into novel technologies and areas are important, as the form the first part of the value chain that eventually ends up in the hands first of industry, then ultimately the consumer

Less toxic chemistry leading to greater environmental conservation- The wider environmental impacts of alternative control strategies that remove the need for traditional chemical control are also central to improving the environment, quality of soil, water and produce. Chloropicrin is a necessary but harmful chemical- if alternatives could be found the environmental benefits would be large.