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Genetic basis of extracellular potato blight recognition in wild Solanum sp.

  • Full or part time
  • Application Deadline
    Applications accepted all year round
  • Competition Funded PhD Project (Students Worldwide)
    Competition Funded PhD Project (Students Worldwide)

Project Description

Potato late blight has caused the devastating Irish potato famine in the 1840s and is still an important pathogen in agriculture today. Potato late blight is caused by the oomycete pathogen Phytophthora infestans, which uses hundreds of secreted effector proteins to manipulate its host. Extracellular proteases are an important defence of host plants against P. infestans. This is testified by the facts that protease depletion increases susceptibility, and that P. infestans produces effectors that inhibit proteases (EpiCs, Epis) or prevent their secretion (AVRblb2).
During a screen of wild Solanum species, we have discovered wild potato and tomato plants that display a hypersensitive cell death response (HR) upon injection with EpiC proteins, but not upon injection with EpiC proteins that lack the protease inhibitory motif (Malik et al., unpublished). This indicates that EpiCs are recognised by these plants through its binding to a protease. This is reminiscent to the recognition in tomato of fungal effector protein Avr2, which binds to the secreted host protease Rcr3 and is recognised by cell surface receptor Cf-2, leading to HR (Rooney et al., 2005). EpiC recognition in wild tomato/potato, however, does not require Cf-2 or Rcr3, because transcript depletion of these genes by virus-induced gene silencing (VIGS) blocks Avr2 recognition, but not EpiC recognition. However, silencing of co-receptor Sobir1 blocks EpiC recognition, implicating the requirement of a receptor-like protein (RLP).
The project AIM is to identify the genes responsible for EpiC recognition in wild tomato and potato, and study their evolution and exploitation as durable resistance genes in agriculture. We will follow both a candidate gene approach and a gene-mapping approach. In the candidate gene approach, we will deplete different proteases and RLPs by VIGS to identify proteases and RLPs required for EpiC-triggered HR. In parallel, we will clone candidate genes and co-express them with EpiC and screen for HR. The gene mapping approach will include next generation sequencing. Once identified, the genes will be tested in transient assays and transgenic plants for providing resistance to P. infestans. Finally, the distribution and evolution of the identified genes can be studied in Solanum populations, taking advantage of the large germplasm available


STUDENT PROFILE

We are looking for an enthusiastic DPhil student with experience in molecular cloning and a passion for working with plant pathogens with an international and interdisciplinary research team.

APPLICATION DEADLINES

There are three application deadlines, but you are strongly encouraged to apply in November or January.

- Friday 16 November 2018
- Friday 25 January 2019
- Friday 1 March 2019

* Note: Applications must be submitted by 12 noon (midday) on these days.

Please ensure that you contact potential supervisors well in advance of these deadlines. Later applications may be considered if places are available.

Funding Notes

Prospective students are encouraged to apply to the Oxford Interdisciplinary Bioscience DTP. International applicants are encouraged to explore scholarship options that are available to them through the University of Oxford, their home countries or organisations such as the Commonwealth Scholarship Commission.

References

Ilyas et al. (2015) Functional divergence of two secreted immune proteases of tomato. Curr. Biol. 25, 2300-2306.
Dong et al. (2014) Effector specialization in a lineage of the Irish potato famine pathogen. Science 343, 552-555.
Bozkurt et al. (2011) Phytophthora infestans effector AVRblb2 prevents secretion of a plant immune protease at the haustorial interface. PNAS 108, 20832-20837.
Kaschani t al. (2010) An effector-targeted protease contributes to defense against Phytophthora infestans and is under diversifying selection in natural hosts. Plant Physiol. 154, 1794-1804. Rooney et al. (2005) Cladosporium Avr2 inhibits tomato Rcr3 protease required for Cf-2-dependent disease resistance. Science 308, 1783-1789.

Related Subjects

How good is research at University of Oxford in Biological Sciences?

FTE Category A staff submitted: 223.80

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