Light is essential for regulating every aspect of plant growth and development. Recent studies have revealed that light quality and duration can influence plant immune response onset as well as the virulence of some pathogens. Phytophthora infestans, the casual agent of Potato Late Blight, secretes effector proteins characterised by an RXLR motif which are translocated into host cells during infection to manipulate the host to benefit the pathogen. A number of RXLR effectors target host proteins with roles in light-mediated responsesto both blue and red light. Thus, pathogen effectors are tools to reveal the strategies by which pathogens can remodel light and immunity responsiveness in their hosts.
Potato NRL protein for chloroplast movement (NCH1) is targeted by a P. infestans RXLR Pi02860 effector.
The effector protein, Pi02860 from P. infestans, targets a potato NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3) and ROOT PHOTOTROPISM 2 (RPT2)-like (NRL) family member, which is an orthologue of Arabidopsis NCH1. NRLs are widespread in land plants and often act as substrate adaptors for the Cullin-RING E3 ubiquitin ligase (CUL3) complex involved in protein ubiquitination. RPT2 and NCH1 are NRL family members known to transduce signals from the blue light receptors, phototropins to regulate chloroplast movement.
Potato Phytochrome B is targeted by a P. infestans RXLR effector, Pi06099.
The essential effector protein, Pi06099 from P. infestans interacts with Potato Phytochrome B to suppress immunity. Phytochrome B is synthesised in its inactive form and is activated by red light. Phytochrome B is involved in regulating germination, inhibition of elongation, shade avoidance, chloroplast development, leaf expansion, flowering, JA and SA signalling, disrupts COP1/SPA complex and differentially modulates PIF and HY5 transcription factor activities. We are currently investigating the role of Pi06099 on red light-regulated immunity that could be exploited to boost crop immunity.
In collaboration with Paul Birch [2], Gabriela Toledo-Ortiz [3], Ingo Hein [4] and Gaynor McKenzie we are currently investigating the role of light quality, intensity and duration on plant development and plant health. We will be investigating the diversity of these responses in Solanum accessions from our Commonwealth Potato Collection [5].
At least 90 species of Phytophthora have been isolated from a wide range of horticultural crop plants worldwide and improvements in molecular diagnostics are continually identifying more. Although several species of Phytophthora can infect raspberry (P. syringae, P. drechsleri, P. cactorum, P. cambivora and P. megasperma), P. rubi is the most common causal agent of the devastating root rot and cane death disease in raspberry. P. rubi belongs to clade 7 of the Phytophthora (“plant destroyer”) phylogeny along with other root rot causing Phytophthoras of warmer climates such as P. cinnamomi and P. sojae.
Raspberry root rot disease, first identified in Europe in the 1980s, is now a widespread contaminant of established raspberry plantations and the disease, once established is extremely difficult to control. The major impact of root rot disease is causing a rapid decline in raspberry plantations grown in soil by more than 70%. Farmers worldwide are being driven to switch to annual replenishment of pot-based systems or adapting to growing alternative fruit crops. Europe is the largest producer of raspberries worldwide and the industry (worth est. €2.2 billion) is being devastated by root rot disease. See Raspberry genetics [6] for more information.
Understanding how organisms distinguish friend from foe is one of the key and fascinating questions in biology. I am currently building a team to investigate the population genomics of P. rubi, determine its pathogenicity arsenal and better understand the enigmatic relationship between root infecting oomycetes and the host rhizosphere.
Visit the following pages for additional information: Julie Graham [7], Craig Simpson [8], Linda Milne, Susan Macallum, Ingo Hein [9] and Steve [10]Whisson [10].
Can soft fruit species engage with beneficial microorganisms and restrict oomycete pathogens? (2022-2026)
Arbuscular mycorrhizal fungi (AMF) grow in association with the roots of over 70% of plant species. These fungi form a network of hyphae which supplies nutrients and water to the plants, while the plants supply hydrocarbons to the fungi. However, impacts go far beyond this exchange and AMF can impact almost every aspect of plant growth and health. This project aims to investigate the AMF species and isolates which associate with raspberry plants and determine their impact on plant growth and the development of phytophthora root rot.
Studying the mechanism of auxin regulated resistance in Raspberry Root Rot caused by Phytophthora rubi (2019-2023)
This study aimed at understanding the mechanism of host resistance in raspberry during PRR development. RNA-sequencing was utilised to study host and pathogen responses at a molecular level. The transcriptional response of raspberry roots to P. rubi infection was examined in a resistant (Latham) and a susceptible (Glen Moy) cultivar. Several pathogenesis-related (PR) genes, along with a selected number of auxin-related genes, were significantly upregulated in infected Latham, prompting an inquiry into the influence of auxin on the pathogen and root-pathogen system. To assess auxin's impact on pathogen growth, P. rubi isolates were screened with different chemicals related to auxin or auxin transport inhibitors. Analysing transcriptional responses of the pathogen to these treatments led to the identification of important genes that may have a putative role in fungicide resistance. Furthermore, the host transcriptional response to infection and treatment with an auxin transport inhibitor, was studied. This led to the identification of PR genes and auxin-related genes related to host resistance. Several genes upregulated in infected Latham were also upregulated in auxin transport inhibitors + infected roots. Moreover, a gene encoding a germin-like auxin-binding protein, ABP19 was highly expressed under both experimental conditions which was found to be closely located to a root rot resistant marker in Latham. Raspberry ABP19 genes were characterised and their role in host resistance was investigated.
Advances made in the understanding of the biology and genetics of Phytophthora rubi and Phytophthora fragariaePhD Project (2017-2021)
This project aimed to increase the understanding of P. rubi and P. fragariae. Phenotypic studies showed their potential to adapt to current control chemicals and to changing climatic conditions. Parallel genetic studies, using target enrichment sequencing on pathogen sequences associated with virulence (PenSeq), found evidence for variation in the effector families between and within species and suggests that P. rubi has significant potential for adaptation and evolution to adjust to environmental stresses in the field. Finally a propagate raspberries was developed, using hydroponics systems, to grow soft fruits disease-free in fully controlled environments for infection assays. This allowed us to follow the life cycle of P. rub,i in a number of Raspberry cultivars with ranging susceptibilities and root architecture, using recently generated GFP and TdT expressing fluorescent strains.
This work provides scientific knowledge to help strengthen the horticultural industry by supporting the existing raspberry breeding programmes at JHL (Nikki Jennnings) and development of novel pathogen control approaches with the soft fruit genetics group.
These projects are linked to on going activities funded by RESAS in JHI-B1-1: Protecting Scotland's crops - Disease Resistance and Pathogen Biology.
Work package lead for WP3: Plant Soil interface
UKRI Crop Pest and Disease 2022 "Seeking new tools to manipulate soil and root microbiology for biocontrol of soft fruit Phytophthora diseases" with Susan McCallum, Andy Taylor, Julie Graham
Innovate UK grant 48163- "RASP" Examining the link between root architecture and auxin on Raspberries resistance to root rot pathogen P. rubi
BSA Rural Community Event "Super Spud" 12th March 2023
BSPP knowledge exchange grant "Super Spuds” exhibit and teaching resources. Funded generation of graphics, teaching resources and primary school visit and activity. 2023
Investigating the virulence function of P. infestans effectors in the manipulation of the host to cause disease (2008-2020)
Genomia Fund (2013-2016) with Industrial Support
Links:
[1] https://orcid.org/0000-0002-5301-4268
[2] https://www.hutton.ac.uk/staff/paul-birch
[3] https://www.hutton.ac.uk/staff/gabriela-toledo-ortiz
[4] https://www.hutton.ac.uk/staff/ingo-hein
[5] https://ics.hutton.ac.uk/germinate-cpc/#/home
[6] http://www.hutton.ac.uk/research/groups/cell-and-molecular-sciences/soft-fruit-genetics/rubus
[7] http://www.hutton.ac.uk/staff/julie-graham
[8] http://www.hutton.ac.uk/staff/craig-simpson
[9] http://www.hutton.ac.uk/staff/ingo-hein
[10] http://www.hutton.ac.uk/staff/stephen-whisson