ProfessorColin Turnbull

Overview
We work on plant immunity, mainly against aphids, that represent major insect pests. We are main focussed on aphid salivary effectors that either activate or suppress plant immunity, leading to incompatible or compatible interactions. Some of our successful approaches centre on functional genomics, specifically proteomics and transcriptomics in combination with the widespread availability of mutants and transgenics. In our plant-aphid model system, we find species-wide diversity of both pest virulence and host resistance (Kanvil et al. 2014) and genetic variation in the complements of aphid effectors in saliva (Kanvil et al. 2015; Thorpe et al. 2024). We have previously invested time in developing tools for studying systemic signalling in Arabidopsis, especially micro-grafting (Turnbull et al. 2002) and sap sampling, and have published both on phloem (Corbesier et al. 2007; Truman et al. 2007; Zhang et al. 2010) and on xylem (Foo et al. 2007) systems.

Current funded research: 

Molecular Biology of aphid virulence and host plant resistance
BBSRC project 2023-2026: Functions of a novel chitinase-like effector family unique to aphids

Virulent pea aphid feeding on Medicago host

Aphids are major worldwide crop pests that cause damage by feeding on phloem sap and frequently by acting as vectors for transmission of numerous viruses. Although some aphid resistance genes have been identified in host plants, very little is known of aphid genetics in relation to why some genotypes are highly virulent on particular hosts and not others. Aphids deliver effector molecules into the host, in an analogous manner to effector delivery from bacterial, fungal and oomycete pathogens. But we know little of aphid effector targets in host plants that result in immune suppression or metabolic reprogramming. Equally, we do not yet know the pathways that lead to effective resistance in presence of appropriate R-genes: what kills or deters aphids? We have screened for candidate effectors by transcriptomics and proteomics, leading to identification of a novel class of proteins with weak homologies to chitinases, that we call CHitinase-Like (CHL), that are abundant in saliva but completely uncharacterised. These proteins are unique to aphids, and may provide clues to their global success as phloem-feeders. Our new BBSRC-funded project is exploring the biochemical functions of CHL proteins, and examining mechanisms of host immune suppression by aphids.

AlphaFold model of CHL1 protein, with predicted docking of chitin oligomer ligand

Selected Research Papers 

Thorpe P, Altmann S, Lopez-Cobollo R et al. (2024) Multi-omics approaches define novel aphid effector candidates associated with virulence and avirulence phenotypes. BMC Genomics 25: 1065 Link https://doi.org/10.1186/s12864-024-10984-x

Antoniadi I, Novák O, Gelová Z et al., 2020, Cell-surface receptors enable perception of extracellular cytokinins. Nature Communications 11: 4284. Link https://www.nature.com/articles/s41467-020-17700-9

Antoniadi I, Plackova L, Simonovik B, et al., 2015, Cell-Type-Specific Cytokinin Distribution within the Arabidopsis Primary Root Apex, Plant Cell, 27, 1955-1967 Link

Kanvil S, Collins CM, Powell G, Turnbull CGN. (2015) Cryptic virulence and avirulence alleles revealed by controlled sexual recombination in pea aphids. Genetics 199: 581-593.

Kanvil K Powell G Turnbull C (2014) Pea aphid biotype performance on diverse Medicago host genotypes indicates highly specific virulence and resistance functions. Bulletin of Entomological Research 6: 689-701. doi.org/10.1017/S0007485314000443

Bromley JR, Warnes BJ, Newell CA, Thomson JC, James CM, Turnbull CGN, Hanke DE (2014) A purine nucleoside phosphorylase in Solanum tuberosum L. (potato) with specificity for cytokinins contributes to the duration of tuber endodormancy. Biochemical J. 458, 225-37.biochemj.org/bj/458/bj4580225.htm

Turnbull CGN, Lopez-Cobollo RM (2013) Tansley Review: Heavy traffic in the fast lane: long-distance signalling by macromolecules. New Phytol, Vol:198, Pages:33-51 http://onlinelibrary.wiley.com/doi/10.1111/nph.12167/abstract

Turnbull C (2011) Long-distance regulation of flowering time. J Exp Bot, 62, 4399-4413 http://jxb.oxfordjournals.org/content/62/13/4399 (doi)

Zhang B, Tolstikov V, Turnbull C, Hicks LM, Fiehn O (2010) Divergent metabolome and proteome suggest functional independence of dual phloem transport systems in cucurbits. Proceedings of the National Academy of Sciences USA 107, 13532-13537. http://www.pnas.org/content/early/2010/06/10/...

Corbesier L, Vincent C, Jang S, Fornara F, Fan Q, Searle I, Giakountis A, Farrona S, Gissot L, Turnbull C, Coupland G (2007) FT protein movement contributes to long-distance signalling in floral induction of Arabidopsis, Science 316, 1030 - 1033. www.sciencemag.org/cgi/content/abstract/316/5827/1030

Foo E, Morris SE, Parmenter K, Yo ung N, Wang H, Jones A, Rameau C, Turnbull CGN, Beveridge CA (2007) Feedback regulation of xylem cytokinin content is conserved in pea and Arabidopsis. Plant Physiology, 143, 1418-1428 www.plantphysiol.org/cgi/content/abstract/143/3/1418

Truman W, Bennett MH, Kubigsteltig I, Turnbull C, Grant M. ( 2007) Arabidopsis systemic immunity uses conserved defense signalling pathwa ys and is mediated by jasmonates. Proceedings of the National Academy of Sciences USA 104, 1075-1080. www.pnas.org/cgi/content/abstract/104/3/1075

Turnbull CGN, Booker JP, Leyser HMO (2002) Micrografting techniques for testing long-distance signalling in Arabidopsis. Plant Journal 32, 255-262.