Plant pathogen interactions

Research

One of the most significant questions in plant pathology is: How do pathogens suppress or otherwise manipulate host defences to establish disease? To do this, they secrete proteins and other chemicals that can interact with the host cell. In some cases, virulence determinants called effector proteins are delivered (translocated) inside living host cells where they ‘re-programme’ defences and metabolism to the pathogen’s benefit.

My group mainly studies effector proteins from the potato late blight pathogen, Phytophthora infestans. P. infestans is an oomycete, a eukaryotic pathogen with a fungus-like lifestyle that develops haustoria - finger-like cell structures that form an intimate interaction with the host plasma membrane during the early stages of disease.  We have shown that haustoria are a major site of delivery of a class of proteins called RXLR effectors. The RXLR motif within these secreted effectors is required for their translocation inside host cells. In the genome of P. infestans we predict that there are >425 RXLR effector genes, demonstrating a remarkable potential for manipulation of host processes. We are discovering that RXLR effectors interact directly with a range of regulatory proteins in the host cell to suppress or otherwise manipulate plant defences. In contrast, the RXLRs are also targets for host resistance proteins which activate immune responses that prevent further colonization by the pathogen.

 

 

 

 

 

 

 

 

 Using comparative and functional genomics, the key questions we are addressing are:

1. How are RXLR effectors delivered into host plant cells?


2. When are RXLR proteins required by the pathogen and where are they localized during infection?


3. What are the host targets of RXLR effectors and what roles do those targets play in plant defence or metabolism?


4. How are RXLR effectors co-evolving with their targets in the host, and how are they evolving to evade detection by the plant immune system?

With other members of the Dundee Effector Consortium (http://www.hutton.ac.uk/research/groups/cell-and-molecular-sciences/dundee-effector-consortium) we are exploiting our understanding of effector biology and diversity within pathogen populations to seek corresponding resistance genes in both host and non-host plants. In particular, we are searching for plant genes that provide durable disease resistance to P. infestans, and to a range of other economically damaging pests and pathogens of Solanaceae crop species (potato, tomato and pepper).

Teaching

Publications

Gilroy EM, Breen S, Whisson S, Squire J, Hein I, Lokossou A, Boevink P, Pritchard L, Avrova AO, Turnbull D, Kaczmarek M, Cano L, Randall E, Lees, A, Govers F, van West P., Kamoun S, Vleeshouwers V, Cooke D, Birch PRJ (2011) Presence/absence, differential expression and sequence polymorphisms between PiAVR2 and PiAVR2-like in Phytophthora infestans determine virulence on R2 plants. New Phytologist 191:763-766.

Gilroy EM, Taylor RM, Hein I, Sadanandom A, Birch PRJ (2011) CMPG1-dependent cell death follows perception of pathogen elicitors at the host plasma membrane and is suppressed by Phytophthora infestans RXLR effector AVR3a. New Phytologist 190:653-666.

Pritchard L, Birch PRJ (2011) A systems biology perspective on plant-microbe interactions; biochemical and structural targets of pathogen effectors. Plant Science 180:584-603.

Bos JI, Armstrong MR, Gilroy EM, Boevink PC, Hein I, Taylor RM, Tian Z, Engelhardt S, Vetukuri R, Harrower B, Dixelius C, Bryan G, Sadanandom A, Whisson SC, Kamoun S, Birch PRJ(2010). Phytophthora infestanseffector AVR3a is essential for virulence and manipulates plant immunity by stabilizing host E3 ligase CMPG1. Proc Natl Acad Sci USA. 107:9909-9914.

Haas B, Kamoun S et al (2009) The genome sequence of the Irish famine pathogen Phytophthora infestans. Nature 461: 393-398.

Hein I, Gilroy EM, Armstrong MR, Birch PRJ(2009). The zig-zag-zig in oomycete-plant interactions. Mol Plant Pathol. 10:547-562.

Birch PRJ, Boevink PC, Gilroy EM, Hein I, Pritchard L, Whisson SC. (2008) RXLR effectors: delivery, functional redundancy and durable disease resistance. Curr Opin Plant Biol 11:373-379.

Whisson SC, Boevink PC, Moleleki L, Avrova AO, Morales J, Gilroy EM, Armstrong MR, Grouffaud S, van West P, Chapman S, Hein I, Toth IK, Pritchard L, Birch PRJ (2007) A translocation signal for delivery of oomycete effector proteins inside host plant cells. Nature 450:115-118.

Birch PRJ, Rehmany AP, Pritchard L, Kamoun S, Beynon JL (2006) Trafficking Arms: Oomycete Effectors Enter Host Plant Cells. Trends in Microbiology 14:8-11.

Rehmany AP, Gordon A, Rose, LE, Allen RL, Armstrong MR, Whisson SC, Kamoun S, Birch PRJ, Beynon, JL (2005) Differential recognition of highly divergent downy mildew avirulence gene alleles by RPP1 genes from two Arabidopsis lines. The Plant Cell17:1839-1850.

Armstrong MR, Whisson SC, Pritchard L, Bos JIB, Venter E, Avrova AO, Rehmany AP, Böhme U, Brooks K,Cherevach I, Hamlin N, White B, Fraser A, Lord A, Quail M, Churcher C, Hall N, Berriman M, Huang S,Kamoun S, Beynon JL, Birch PRJ (2005) An Ancestral Oomycete Locus Contains Late Blight Avirulence Gene Avr3a, Encoding a Protein that is Recognised in the Host Cytoplasm. Proc. Natl. Acad. Sci. (USA).102:7766-7771.