Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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Item Molecular Investigation of Rlm3 From Rapeseed as a Potential Broad-Spectrum Resistance Gene Against Fungal Pathogens Producing Structurally Conserved Effectors(John Wiley and Sons Ltd on behalf of British Society for Plant Pathology, 2025-09-21) Talbi N; Pakzad S; Blaise F; Ollivier B; Rouxel T; Balesdent M-H; Blondeau K; Lazar N; van Tilbeurgh H; Mesarich CH; Fudal IRecognition of a pathogen avirulence (AVR) effector protein by its cognate plant resistance (R) protein triggers immune responses that are typically sufficient to provide effective disease control. While AVR effectors have long been considered species- or genotype-specific, several studies have recently shown that these proteins belong to a limited set of structural families. This finding paves the way for the identification or engineering of broad-spectrum R proteins capable of recognising several members of the same structural family. In the Leptosphaeria maculans–rapeseed (Brassica napus) pathosystem, 13 AVR genes have been cloned, of which four encode effectors belonging to the LARS (Leptosphaeria AviRulence and Suppressing) structural family. Homologues of the L. maculans AvrLm3 AVR protein, a LARS family member, have been identified in other fungal species, including an AVR protein from Fulvia fulva, Ecp11-1. We have previously shown that Ecp11-1 is recognised by rapeseed varieties carrying the Rlm3 R gene, and that this recognition is masked in the presence of another LARS AVR gene, AvrLm4-7. In this study, we expanded our characterisation of the Rlm3 resistance spectrum to effectors from Fusarium oxysporum and Zymoseptoria ardabiliae. Like Ecp11-1, we showed that an effector from F. oxysporum f. sp. narcissi is recognised by Rlm3, and that this recognition is masked in the presence of AvrLm4-7. We also investigated which protein regions and amino acids are necessary for AvrLm3 and Ecp11-1 recognition by Rlm3. This analysis is a first step towards the identification of broad-spectrum R proteins that confer protection against multiple phytopathogens.Item Development of a validated efficient HPLC-DAD analysis for assessing polyphenol transformation during black tea processing(Elsevier Inc, 2025-12-01) Muthulingam P; Popovich DG; Nimal Punyasiri PA; Nanayakkara CM; Mesarich CH; Rashidinejad ATea (Camellia sinensis) is valued for its polyphenolic compounds, which define its sensory and health attributes. Accurate quantification across processing stages is hindered by analytical and extraction challenges. We developed and validated a rapid high-performance liquid chromatography with diode array detection (HPLC-DAD) method for simultaneous analysis of 12 key constituents - gallic acid, theobromine, caffeine, (+)-catechin (C), (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG), theaflavin (TF), theaflavin-3-gallate (TF3G), theaflavin-3′-gallate (TF3’G), theaflavin-3,3′-digallate (TF3–3’G), in green and black tea. The method achieved superior linearity (r² > 0.9995), high sensitivity (LOD: 0.03–1.68 µg/mL), strong precision (RSD < 4.68 %), and high recovery, while also resolving co-elution with a 40-min runtime. Extraction was optimized using ultrasonication with 70 % methanol, which outperformed hot water and ISO-standard methods. Applied to black tea processing, the method revealed a 79.1 % reduction in catechins, post-rolling theaflavin peaks, and dynamic fluctuations in gallic acid, caffeine, and theobromine. These changes were associated with enzymatic oxidation, leaching, and cultivar effects. The validated HPLC-DAD method provides a robust tool for tea polyphenol profiling and enables improved understanding of processing-induced transformations. It holds potential for use in quality control, nutritional labeling, and functional food research in tea and other polyphenol-rich systems.Item Effector loss drives adaptation of Pseudomonas syringae pv. actinidiae to Actinidia arguta(2021-11-15) Hemara LM; Jayaraman J; Sutherland PW; Montefiori M; Arshed S; Chatterjee A; Chen R; Andersen M; Mesarich CH; van der Linden O; Schipper MM; Vanneste JL; Brendolise C; Templeton MDItem Variation at the common polysaccharide antigen locus drives lipopolysaccharide diversity within the P. syringae species complex(2020-04-01) Jayaraman J; Jones WT; Harvey D; Hemara LM; McCann HC; Yoon M; Warring SL; Fineran PC; Mesarich CH; Templeton MDItem Genomic, effector protein and culture-based analysis of Cyclaneusma minus in New Zealand provides evidence for multiple morphotypes(2023-05-21) Tarallo M; Dobbie K; Leite LN; Waters T; Gillard K; Sen D; McDougal RL; Mesarich CH; Bradshaw REItem Sequential breakdown of the complex Cf-9 leaf mould resistance locus in tomato by Fulvia fulva(2023-08-27) de la Rosa S; Schol CR; Peregrina ÁR; Winter DJ; Hilgers AM; Maeda K; Iida Y; Tarallo M; Jia R; Beenen HG; Rocafort M; de Wit PJGM; Bowen JK; Bradshaw RE; Joosten MHAJ; Bai Y; Mesarich CHItem Genomic and culture-based analysis of Cyclaneusma minus in New Zealand provides evidence for multiple morphotypes(BioMed Central Ltd, 2024-12) Tarallo M; Dobbie KB; Leite LN; Waters TL; Gillard KNT; Sen D; Mesarich CH; Bradshaw RE; McDougal RLCyclaneusma needle cast, caused by Cyclaneusma minus, affects Pinus species world wide. Previous studies suggested the presence of two distinct morphotypes in New Zealand, ‘verum’ and ‘simile’. Traditional mycological analyses revealed a third morphotype with clear differences in colony morphology and cardinal growth rates at varying temperatures. Genome sequencing of eight C. minus isolates provided further evidence of the existence of a third morphotype, named as ‘novus’ in this study. To further analyse these morphotypes, we predicted candidate effector proteins for all eight isolates, and also characterized a cell-death eliciting effector family, Ecp32, which is present in other pine phytopathogens. In concordance with their distinct classification into three different morphotypes, the number of Ecp32 family members differed, with patterns of pseudogenization in the ‘simile’ morphotype, and some members being found exclusively either in the ‘simile’ or ‘verum’ morphotypes. We also showed that the Ecp32 family proteins trigger cell death in non-host Nicotiana species, and, as previously demonstrated in other plant pathogens, the Ecp32 family proteins in C. minus adopt a β-trefoil fold. These analyses provide further evidence that the three morphotypes might be distinct species that need formal descriptions. Understanding the geographical range of different Cyclaneusma species and variations in virulence and pathogenicity will provide a better understanding of pine needle diseases and enable the development of more durable methods to control this disease.Item Characterization of two conserved cell death elicitor families from the Dothideomycete fungal pathogens Dothistroma septosporum and Fulvia fulva (syn. Cladosporium fulvum)(Frontiers Media S.A., 2022-09-08) Tarallo M; McDougal RL; Chen Z; Wang Y; Bradshaw RE; Mesarich CH; Wang YDothistroma septosporum (Ds) and Fulvia fulva (Ff; previously called Cladosporium fulvum) are two closely related Dothideomycete fungal species that cause Dothistroma needle blight in pine and leaf mold in tomato, respectively. During host colonization, these pathogens secrete virulence factors termed effectors to promote infection. In the presence of corresponding host immune receptors, however, these effectors activate plant defenses, including a localized cell death response that halts pathogen growth. We identified two apoplastic effector protein families, Ecp20 and Ecp32, which are conserved between the two pathogens. The Ecp20 family has four paralogues in both species, while the Ecp32 family has four paralogues in D. septosporum and five in F. fulva. Both families have members that are highly expressed during host infection. Members of the Ecp20 family have predicted structural similarity to proteins with a β-barrel fold, including the Alt a 1 allergen from Alternaria alternata, while members of the Ecp32 family have predicted structural similarity to proteins with a β-trefoil fold, such as trypsin inhibitors and lectins. Using Agrobacterium tumefaciens-mediated transient transformation assays, each family member was assessed for its ability to trigger cell death in leaves of the non-host species Nicotiana benthamiana and N. tabacum. Using this approach, FfEcp20-2, DsEcp20-3, and FfEcp20-3 from the Ecp20 family, and all members from the Ecp32 family, except for the Ds/FfEcp32-4 pair, triggered cell death in both species. This cell death was dependent on secretion of the effectors to the apoplast. In line with recognition by an extracellular immune receptor, cell death triggered by Ds/FfEcp20-3 and FfEcp32-3 was compromised in N. benthamiana silenced for BAK1 or SOBIR1, which encode extracellular co-receptors involved in transducing defense response signals following apoplastic effector recognition. We then investigated whether DsEcp20-3 and DsEcp20-4 triggered cell death in the host species Pinus radiata by directly infiltrating purified protein into pine needles. Strikingly, as in the non-host species, DsEcp20-3 triggered cell death, while DsEcp20-4 did not. Collectively, our study describes two new candidate effector families with cell death-eliciting activity from D. septosporum and F. fulva and provides evidence that members of these families are recognized by plant immune receptors.Item Cell Wall Carbohydrate Dynamics during the Differentiation of Infection Structures by the Apple Scab Fungus, Venturia inaequalis.(American Society for Microbiology, 2023-06-15) Rocafort M; Srivastava V; Bowen JK; Díaz-Moreno SM; Guo Y; Bulone V; Plummer KM; Sutherland PW; Anderson MA; Bradshaw RE; Mesarich CH; Wang YScab, caused by the biotrophic fungal pathogen Venturia inaequalis, is the most economically important disease of apples. During infection, V. inaequalis colonizes the subcuticular host environment, where it develops specialized infection structures called runner hyphae and stromata. These structures are thought to be involved in nutrient acquisition and effector (virulence factor) delivery, but also give rise to conidia that further the infection cycle. Despite their importance, very little is known about how these structures are differentiated. Likewise, nothing is known about how these structures are protected from host defenses or recognition by the host immune system. To better understand these processes, we first performed a glycosidic linkage analysis of sporulating tubular hyphae from V. inaequalis developed in culture. This analysis revealed that the V. inaequalis cell wall is mostly composed of glucans (44%) and mannans (37%), whereas chitin represents a much smaller proportion (4%). Next, we used transcriptomics and confocal laser scanning microscopy to provide insights into the cell wall carbohydrate composition of runner hyphae and stromata. These analyses revealed that, during subcuticular host colonization, genes of V. inaequalis putatively associated with the biosynthesis of immunogenic carbohydrates, such as chitin and β-1,6-glucan, are downregulated relative to growth in culture, while on the surface of runner hyphae and stromata, chitin is deacetylated to the less-immunogenic carbohydrate chitosan. These changes are anticipated to enable the subcuticular differentiation of runner hyphae and stromata by V. inaequalis, as well as to protect these structures from host defenses and recognition by the host immune system. IMPORTANCE Plant-pathogenic fungi are a major threat to food security. Among these are subcuticular pathogens, which often cause latent asymptomatic infections, making them difficult to control. A key feature of these pathogens is their ability to differentiate specialized subcuticular infection structures that, to date, remain largely understudied. This is typified by Venturia inaequalis, which causes scab, the most economically important disease of apples. In this study, we show that, during subcuticular host colonization, V. inaequalis downregulates genes associated with the biosynthesis of two immunogenic cell wall carbohydrates, chitin and β-1,6-glucan, and coats its subcuticular infection structures with a less-immunogenic carbohydrate, chitosan. These changes are anticipated to enable host colonization by V. inaequalis and provide a foundation for understanding subcuticular host colonization by other plant-pathogenic fungi. Such an understanding is important, as it may inform the development of novel control strategies against subcuticular plant-pathogenic fungi.Item Why a strategic shift in action is needed to recognise and empower Indigenous plant pathology knowledge and research(Springer Nature on behalf of the Australasian Plant Pathology Society Inc, 2024-05-01) Ehau-Taumaunu H; Williams NM; Marsh A; Waipara NW; Higgins CM; Geering ADW; Mesarich CH; Rigano LA; Summerell BA; Johnson GI; Williamson P; MacDiarmid RMPlant pathology researchers play a pivotal role in thought leadership and its translation to action regarding the recognition and demonstration of the value of Indigenous knowledge and science. For many scientists, navigating the space of Indigenous rights and perspectives is challenging. In pursuit of a cultural shift in research and development within the field of plant pathology, the 2019–2021 Management Committee of the Australasian Plant Pathology Society (APPS) undertook a review and modernization of the Society’s Constitution. The aim was to ensure its alignment with principles that foster inclusivity of Indigenous peoples in the development and implementation of relevant research projects impacting their communities. Additionally, a dynamic repository of guidelines and resources was compiled. These resources are designed to assist plant pathologists, while respecting and not superseding the guidance provided by local Indigenous researchers, practitioners, and advisors. The collective efforts of plant pathologists hold immense potential in championing Indigenous Peoples and their rights, steering the field toward a more inclusive and equitable future. This paper builds upon the thesis presented in the APPS Presidential Address at the Biennial APPS Conference in 2021, held virtually in lutruwita (Tasmania) on the unceded lands of the Palawa people. It underscores the potential impact when plant pathologists unite in advocating for Indigenous Peoples and their rightful place within the field.
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