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An Easy and Flexible Inoculation Method for Accurately Assessing Powdery Mildew-Infection Phenotypes of Arabidopsis and Other Plants
Published on: March 9, 2021
Monocot and dicot MLO powdery mildew susceptibility factors are functionally conserved in spite of the evolution of
Michela Appiano1, Domenico Catalano2, Miguel Santillán Martínez1
1Wageningen UR Plant Breeding, Wageningen University & Research Centre, Droevendaalsesteeg 1, 6708, PB, Wageningen, The Netherlands.
Background:
Specific members of the plant Mildew Locus O (MLO) protein family act as susceptibility factors towards powdery mildew (PM), a worldwide-spread fungal disease threatening many cultivated species. Previous studies indicated that monocot and dicot MLO susceptibility proteins are phylogenetically divergent.
Methods:
A bioinformatic approach was followed to study the type of evolution of Angiosperm MLO susceptibility proteins. Transgenic complementation tests were performed for functional analysis.
Results:
Our results show that monocot and dicot MLO susceptibility proteins evolved class-specific conservation patterns. Many of them appear to be the result of negative selection and thus are likely to provide an adaptive value. We also tested whether different molecular features between monocot and dicot MLO proteins are specifically required by PM fungal species to cause pathogenesis. To this aim, we transformed a tomato mutant impaired for the endogenous SlMLO1 gene, and therefore resistant to the tomato PM species Oidium neolycopersici, with heterologous MLO susceptibility genes from the monocot barley and the dicot pea. In both cases, we observed restoration of PM symptoms. Finally, through histological observations, we demonstrate that both monocot and dicot susceptibility alleles of the MLO genes predispose to penetration of a non-adapted PM fungal species in plant epidermal cells.
Conclusions:
With this study, we provide insights on the evolution and function of MLO genes involved in the interaction with PM fungi. With respect to breeding research, we show that transgenic complementation assays involving phylogenetically distant plant species can be used for the characterization of novel MLO susceptibility genes. Moreover, we provide an overview of MLO protein molecular features predicted to play a major role in PM susceptibility. These represent ideal targets for future approaches of reverse genetics, addressed to the selection of loss-of-function resistant mutants in cultivated species.
Insights
Plant Mildew Locus O (MLO) proteins are key susceptibility factors for powdery mildew (PM). This study reveals conserved evolution patterns and functional roles of MLO proteins, offering targets for disease-resistant crop development.
Area of Science:
- Plant pathology
- Molecular biology
- Evolutionary biology
Background:
- Mildew Locus O (MLO) proteins are crucial susceptibility factors for powdery mildew (PM), a significant global plant disease.
- Previous research highlighted phylogenetic divergence between monocot and dicot MLO susceptibility proteins.
Purpose of the Study:
- To investigate the evolutionary patterns and functional roles of MLO susceptibility proteins in Angiosperms.
- To identify molecular features of MLO proteins that contribute to PM pathogenesis.
- To explore the potential of transgenic complementation assays for characterizing MLO genes.
Main Methods:
- Bioinformatic analysis of Angiosperm MLO protein evolution.
- Functional analysis using transgenic complementation tests in a tomato powdery mildew-susceptible mutant.
- Histological observations to assess fungal penetration.
Main Results:
- Monocot and dicot MLO susceptibility proteins exhibit class-specific conservation patterns, with many showing signs of negative selection and adaptive value.
- Heterologous expression of MLO genes from barley (monocot) and pea (dicot) restored PM susceptibility in a resistant tomato mutant.
- Both monocot and dicot MLO alleles facilitated the penetration of non-adapted PM fungal species into plant epidermal cells.
Conclusions:
- This study provides key insights into the evolution and function of MLO genes in plant-pathogen interactions.
- Transgenic complementation assays with phylogenetically distant species are effective for characterizing novel MLO susceptibility genes.
- Identified MLO protein molecular features are promising targets for developing disease-resistant crop varieties through reverse genetics.
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