School of plant biology research Project ideas for Prospective 4th

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Resistance to sap-sucking insect pests Winthrop Professor Karam Singh

Dr Lingling Gao

Assistant Professor Lars Kamphuis
Sap-sucking insects, such as aphids, are major pests in agriculture causing direct feeding damage and transmitting over 50% of all plant viruses. The group has built up an excellent system to study sap-sucking insect pests involving the model legume Medicago truncatula and various aphid species including the model aphid, pea aphid. The combination of powerful genetic and genomic tools/resources on both the plant and aphid sides of the interaction enable cutting edge research and its’ application to agriculture. Two potential projects in this area are:
1a) Characterisation of loss of resistance to aphids mutant in the model legume Medicago truncatula: The legume Medicago truncatula cultivar Jester has resistance to three aphid species. A mutagenised Jester plant has been identified that has lost resistance to all three aphids. Resistance to aphids occurs through recognition by independent plants resistance genes for each aphid, which in turn triggers downstream defense responses in the plant. The identified mutant is compromised in resistance to three different aphid species making this a very interesting mutant, with a mutation in a gene that is essential in the downstream signalling cascade to mount a successful defense response to all three aphid species. Detailed characterisation of this mutant and the behaviour of the aphids including feeding behaviour and aphid settling in choice tests and aphid performance when given no choice of plant would shed more light on the resistance mechanisms that have been lost in this mutant plant. The characterisation of classical defense pathways in this mutant will also shed light on which major defense signalling pathways might be affected in this mutant, resulting in the loss of resistance to all three aphid species. The proposed research would expose the student to range of disciplines including physiology, molecular biology, biochemistry and basic bioinformatics, making this an interesting and exciting project.
1b) Characterisation of R gene mediated defences following aphid attack: Resistance to bluegreen aphid is controlled by a single dominant gene termed AKR (Acyrthosiphon kondoi resistance). A pair of near-isogenic lines has been generated which are either resistant (having AKR) or susceptible (lacking AKR) to bluegreen aphid. Potential projects using transcriptomics and/or metabolomics are available to identify key regulators and defence pathways recruited by the AKR resistance gene following recognition of the aphid. The proposed research would expose the student to range of disciplines including molecular biology, biochemistry, metabolomics, proteomics and basic bioinformatics, making this an interesting and exciting project.

2. Resistance to fungal pathogens Winthrop Professor Karam Singh

Assistant Professor Jonathan Anderson

Dr Louise Thatcher
Fungal diseases are major problems for Australian agriculture. One such important pathogen, R. solani, causes substantial losses to wheat, barley, canola and various legumes in Australia. Internationally it is the second most important disease problem for the world’s largest staple food, rice. Another devastating fungal pathogen is Fusarium oxysporum, causal agent of Fusarium vascular wilt and able to infect over 100 plant species including grain legumes (e.g. chickpea, lupin) and oil seed crops (e.g. canola, cotton).

Internationally, Fusarium wilt disease can cause losses of 10-100% in chickpea. Australia is currently free from isolates capable of infecting our major grain legumes (chickpea, lupin and lentil) however, the pathogen presents as a high biosecurity threat to these industries. The group uses powerful genomic and bioinformatic approaches on both the plant and pathogen side to unravel the mechanisms underlying resistance or susceptibility.
2a) Characterise host genes linked to fungal resistance using molecular and reverse genetic approaches: The group has identified specific transcription factors and regulatory genes in both Arabidopsis and M. truncatula that are key mediators of plant defence responses to some fungal pathogens. Potential projects include functional characterisation through transgenic (knockout or overexpression) or mutant lines, and the identification of target genes and partner proteins using molecular and genomic approaches. The identification of regulatory sequences that allow the specific expression of the transcription factors in various plants is also a key component of producing plants with enhanced disease resistance.
2b) Identification of effectors/pathogenicity genes from R. solani or F. oxysporum genomes required for virulence on a plant host: Pathogens employ a sophisticated system of proteins, called effectors, to interact with host proteins and manipulate the plant into susceptibility. Identification of these effectors can reveal the plant targets which may in turn be modified to confer resistance to the pathogen. The group has recently sequenced and assembled genomes for R. solani and F. oxysporum. Using a combination of powerful genetic resources, bioinformatics and molecular biology, putative pathogenicity effectors can be identified and their function in host manipulation investigated.

  1. Novel regulators of biotic and abiotic stress induced responses in plants.

Winthrop Professor Karam Singh

Dr Louise Thatcher
The protection of cells from abiotic or biotic-induced stress is critical for an organism’s survival and a group of ubiquitous enzymes central to this protection are the detoxification family of glutathione S-transferases (GSTs). The research group of Winthrop Professor Singh conducted a genetic screen in the model plant Arabidopsis thaliana for mutants with altered expression of the early stress-responsive marker gene Glutathione S-Transferase Phi8 (AtGSTF8). Several novel mutants isolated from this screen confer altered responses to biotic and/or abiotic stress including increased thermo-tolerance and resistance to one or more fungal pathogens and insect pests.

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