Characterisation of aphid-derived components involved in plant innate immune responses

Canham, James (2022) Characterisation of aphid-derived components involved in plant innate immune responses. Doctoral thesis, University of East Anglia.

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Abstract

As obligate herbivores and important vectors of many plant viruses, aphids represent a considerable and increasing threat to agriculture and food security. An increasing body of evidence suggests that plants may perceive aphid-derived cues during feeding events, resulting in plant innate immune responses. The aim of this thesis is to uncover the underlying aphid and plant components that contribute to the induction of plant innate immunity to aphids.

To reveal the breadth of plant innate immune responses that may be induced upon perception of Myzus persicae, partially purified elicitor fractions were generated from these aphids and used to investigate microbe-associated molecular pattern-triggered immunity (MTI) responses of Arabidopsis thaliana. Fractions strongly induce MTI via activating MAPK cascades and inducing the expression of genes previously shown to impact M. persicae resistance of A. thaliana, such as camalexin biosynthesis pathway genes and WRKY33, a regulator of camalexin production. Furthermore, the co-receptor, SUPPRESSOR OF BIR1-1 (SOBIR1) was found to be required for aphid-derived elicitor-triggered MTI in A. thaliana. As SOBIR1 is required for receptor-like protein (RLP) mediated immunity, a collection of single Atrlp mutant A. thaliana lines were screened for altered MAPK activation to the aphid fractions. In addition, EMS-mutagenised pWRKY33:fLUC seedlings were screened for altered responses to the aphid elicitors. Neither of these screens elucidated obvious receptor candidates suggesting that more than one receptor may be involved in aphid elicitor perception.

Further analysis of aphid-derived fractions suggest that elicitor function is conferred by a peptide and requires proteolytic liberation, most likely by an aphid protease, before inducing MTI in plants. Natural variation for aphid-derived elicitor-induced seedling growth inhibition within A. thaliana accessions validated this approach for future investigations. By revealing novel components of MTI to aphids, this study offers insights into the mechanisms that mediate plant perception of aphid cues.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 29 Jun 2022 11:09
Last Modified: 29 Jun 2022 11:09
URI: https://ueaeprints.uea.ac.uk/id/eprint/85843
DOI:

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