Hydrogen peroxide detoxifying enzymes show different activity patterns in host and non-host plant interactions with Magnaporthe oryzae Triticum pathotype

Role of seed infection for the near and far distance dissemination of wheat blast caused by Magnaporthe oryzae pathotype Triticum

Magnaporthe oryzae pathotype Triticum (MoT) is a devastating fungal phytopathogen causing wheat blast disease which threatens wheat production particularly in warmer climate zones. Effective disease control is hampered by the limited knowledge on the life cycle, epidemiology, and pathogenicity of MoT. Since MoT mainly infects and colonizes the inflorescences of wheat, infection, invasion routes and colonization of MoT on wheat ears and in wheat seeds were investigated in order to assess potential seed transmission pathways. MoT was spray inoculated on two wheat cultivars (Sumai 3, susceptible and Milan, resistant) at three ear maturity stages [full ear emergence, growth stage (GS) 59; mid flowering, GS 65; and end of flowering, GS 69]. Incidence of MoT on Sumai 3 seeds was 100% and 20-25% on Milan. MoT sporulation rate on Sumai 3 contaminated seeds was more than 15 times higher than on Milan. Repeated washes of seed samples for removing paraffin fixation hampers seed microscopy. To overcome the damage of seed samples, we used hand-sectioned seed samples instead of paraffin-fixed microtome samples to facilitate microscopy. The colonization of MoT within various seed tissues was followed by light and confocal laser scanning microscopy (CLSM). Invasion of MoT in seeds predominantly occurred in the caryopsis germ region, but entry via other seed parts was also observed, confirming the potential of intense colonization of MoT in wheat grains. Fungal spread in wheat plants growing from MoT infected seeds was monitored through plating, microscopic and molecular techniques. Under greenhouse conditions, no spread of MoT from infected seeds to seedlings later than GS 21 or to ears was detected, neither in Milan nor in Sumai 3. We therefore conclude, that MoT may not systemically contaminate inflorescences and seeds in neither susceptible nor resistant wheat cultivars. However, initial blast symptoms, only found on seedlings of Sumai 3 but not Milan, resulted in the formation of new conidia, which may serve as inoculum source for plant-to-plant dissemination by airborne infection of plant stands in the field (short distance spread). Ultimately the inoculum may infect young inflorescences in the field and contaminate seeds. Our findings again stress the risk of long-distance dissemination of wheat blast across continents through MoT-contaminated seeds. This underlines the importance of mandatory use of healthy seeds in strategies to control any further spread of wheat blast.

Enzyme activity profiling for physiological phenotyping within functional phenomics: plant growth and stress responses

High-throughput profiling of key enzyme activities of carbon, nitrogen, and antioxidant metabolism is emerging as a valuable approach to integrate cell physiological phenotyping into a holistic functional phenomics approach. However, the analyses of the large datasets generated by this method represent a bottleneck, often keeping researchers from exploiting the full potential of their studies. We address these limitations through the exemplary application of a set of data evaluation and visualization tools within a case study. This includes the introduction of multivariate statistical analyses that can easily be implemented in similar studies, allowing researchers to extract more valuable information to identify enzymatic biosignatures. Through a literature meta-analysis, we demonstrate how enzyme activity profiling has already provided functional information on the mechanisms regulating plant development and response mechanisms to abiotic stress and pathogen attack. The high robustness of the distinct enzymatic biosignatures observed during developmental processes and under stress conditions underpins the enormous potential of enzyme activity profiling for future applications in both basic and applied research. Enzyme activity profiling will complement molecular -omics approaches to contribute to the mechanistic understanding required to narrow the genotype-to-phenotype knowledge gap and to identify predictive biomarkers for plant breeding to develop climate-resilient crops.

On the expansion of biological functions of lytic polysaccharide monooxygenases

Lytic polysaccharide monooxygenases (LPMOs) constitute an enigmatic class of enzymes, the discovery of which has opened up a new arena of riveting research. LPMOs can oxidatively cleave the glycosidic bonds found in carbohydrate polymers enabling the depolymerisation of recalcitrant biomasses, such as cellulose or chitin. While most studies have so far mainly explored the role of LPMOs in a (plant) biomass conversion context, alternative roles and paradigms begin to emerge. In the present review, we propose a historical perspective of LPMO research providing a succinct overview of the major achievements of LPMO research over the past decade. This journey through LPMOs landscape leads us to dive into the emerging biological functions of LPMOs and LPMO-like proteins. We notably highlight roles in fungal and oomycete plant pathogenesis (e.g. potato late blight), but also in mutualistic/commensalism symbiosis (e.g. ectomycorrhizae). We further present the potential importance of LPMOs in other microbial pathogenesis including diseases caused by bacteria (e.g. pneumonia), fungi (e.g. human meningitis), oomycetes and viruses (e.g. entomopox), as well as in (micro)organism development (including several plant pests). Our assessment of the literature leads to the formulation of outstanding questions, promising for the coming years exciting research and discoveries on these moonlighting proteins.