Infection by a foliar endophyte elicits novel arabidopside-based plant defence reactions in its host, Cirsium arvense

Endophytic fungi live asymptomatically within plants. They are usually regarded as non-pathogenic or even mutualistic, but whether plants respond antagonistically to their presence remains unclear, particularly in the little-studied associations between endophytes and nong-raminoid herbaceous plants. We investigated the effects of the endophyte Chaetomium cochlioides on leaf chemistry in Cirsium arvense. Plants were sprayed with spores; leaf material from both subsequent new growth and the sprayed leaves was analysed 2 wk later. Infection frequency was 91% and63% for sprayed and new growth, respectively, indicating that C. cochlioides rapidly infects new foliage. Metabolomic analyses revealed marked changes in leaf chemistry with infection, especially in new growth. Changes in several novel oxylipin metabolites were detected, including arabi-dopsides reported here for the first time in a plant species other than Arabidopsis thaliana,and a jasmonate-containing galactolipid. The production of these metabolites in response to endophyte presence, particularly in newly infected foliage, suggests that endophytes elicit similar chemical responses in plants to those usually produced following wounding, herbivory and pathogen invasion. Whether en-dophytes benefit their hosts may depend on a complex series of chemically mediated interactions between the plant, the endophyte, other microbial colonists and natural enemies

NX Trichothecenes Are Required for Fusarium graminearum Infection of Wheat

Fusarium graminearum causes Fusarium head blight (FHB) on wheat and barley and contaminates grains with various mycotoxins that are toxic to humans and animals. Deoxynivalenol (DON), a type B trichothecene, is an essential virulence factor that is required for F. graminearum to spread within a wheat head. Recently, novel type A trichothecenes NX-2 and NX-3 (NX) have been found in F. graminearum. NX trichothecenes lack a keto group at the C8 position. To determine if NX trichothecenes play a role similar to that of DON during F. graminearum infection, deletion mutants of TRI5, the first gene for trichothecene biosynthesis, were generated from strains PH-1, NRRL46422, and NRRL44211 (hereafter 44211) representing the 15-acetyl-DON, 3-acetyl-DON, and NX chemotypes. No trichothecene production was detected in any of the Δtri5 mutants in cultures or inoculated wheat heads. FHB symptoms were restricted to the inoculated wheat spikelets when point-inoculated with the Δtri5 mutants, confirming the necessity of NX and DON for FHB spread. Furthermore, whole-head dip inoculations revealed significant reductions in disease and fungal biomass in wheat heads inoculated with 44211Δtri5 compared with 44211. Introduction of the native 44211 TRI5 and a Trichoderma arundinaceum TRI5 ortholog in the 44211Δtri5 mutant complemented trichothecene production in vitro; however, introducing both TRI5 partially restored wild-type levels of NX in infected heads. Our results demonstrate that NX trichothecenes play an important role in Fusarium graminearum initial infection as well as FHB spread. Thus, TRI5 may serve as an ideal target to control plant infection, FHB spread, and mycotoxin production simultaneously. [Graphic: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license

Quest Volume 3 Number 4

Contents: Ancient artifacts, adornment, and archaeology - Mapungubwe's precious beads and figurines reveal Africa's distant past: Hidden worlds behind the Milky Way - The Zone of Avoidance, where galaxies have hidden since time began: The state of our environment - Monitoring South Africa's natural resources: Life in estuaries - Pipefish survival: Vulnerable organisms indicate - ecosystem health: Fish larvae smell their way to safety - Discovering what signals attract fishes to their nurseries: What's that brown haze over Cape Town?: Urban air pollution that's dangerous to health: Colour without colour -new generation cosmetics: Photonics and optics light up the way forward: The vitamin B12 story - The pioneering science of Dorothy Hodgkin; Special feature: Science for the Classroom: The search for the missing carbon sink - Max Planck Society: Fact files Environmental facts for South Africa - Some Mapungubwe facts - X-ray crystallography and vitamin 812: Science news -Fighting junk food; Talking heads - How elephants run - Ozone threatens carbon sinks; Beware iPods in a thunderstorm - Tips for decision-makers: QUEST interviews Women in engineering Two prominent civil engineers and their road to success: The S& T tourist Mapungubwe National Park - Repository of natural and human heritage: Careers Working with heritage - Studying astrophysics for related careers: Viewpoint Women in science - cresting the wave or wiped out?: Your questions answered - Gums, badgers, and economics: Top woman researchers newly elected to ASSAf:The Department of Science and Innovation: Academy of Science of South Afric

Overall survival in the OlympiA phase III trial of adjuvant olaparib in patients with germline pathogenic variants in BRCA1/2 and high-risk, early breast cancer

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