Agricultural productivity depends on increasingly extreme weather phenomena, and the use of germplasm that has to be continuously improved by plant breeders to become tolerant to various biotic and ...abiotic stresses. Molecular plant biologists try to understand the mechanisms associated with stress responses and provide knowledge that could be used in breeding programs. To provide a partial overview about our current understanding about molecular and physiological stress responses, and how this knowledge can be used in agriculture, we have edited a special issue on “Biotic and Abiotic Stress Responses in Crop Plants”. Contributions are from different fields including heat stress responses, stress responses during drought and salinity, as well as during flooding, and resistance and susceptibility to pathogenetic stresses and about the role of plant functional metabolites in biotic stress responses. Future research demand in particular areas of crop stress physiology is discussed, as well as the importance of translational research and investigations directly in elite crop plants and in the genetic resources available for breeding.
The plant cuticle and cell wall separate microbial pathogens from the products of plant metabolism. While microbial pathogens try to breach these barriers for colonization, plants respond to ...attempted penetration by a battery of wall-associated defense reactions. Successful pathogens circumvent or suppress plant nonself recognition and basal defense during penetration and during microbial reproduction. Additionally, accommodation of fungal infection structures within intact cells requires host reprogramming. Recent data highlight that both early plant defense to fungal penetration and host reprogramming for susceptibility can function at the host cell periphery. Genetic evidence has also widened our understanding of how fungal pathogens are restricted during penetration at the plant cell wall. This review summarizes the current view of how plants monitor and model their cell periphery during interaction with microbial invaders.
► Plant–powdery mildew interactions are well suited for cell biological analyses. ► Cell-autonomous plant defence responses enable single cell studies. ► MLO proteins are crucial for successful entry ...of powdery mildews into host cells. ► Secretory processes from both organisms occur at the plant–fungus interface. ► Arabidopsis RPW8 is the first plant protein found at the extrahaustorial membrane.
Powdery mildew fungi represent a paradigm for obligate biotrophic parasites, which only propagate in long-lasting intimate interactions with living host cells. These highly specialized phytopathogens induce re-organization of host cell architecture and physiology for their own demands. This probably includes the corruption of basal host cellular functions for successful fungal pathogenesis. Recent studies revealed secretory processes by both interaction partners as key incidents of the combat at the plant–fungus interface. The analysis of cellular events during plant–powdery mildew interactions may not only lead to a better understanding of plant pathological features, but may also foster novel discoveries in the area of plant cell biology.
The exchange of small RNAs (sRNAs) between hosts and pathogens can lead to gene silencing in the recipient organism, a mechanism termed cross-kingdom RNAi (ck-RNAi). While fungal sRNAs promoting ...virulence are established, the significance of ck-RNAi in distinct plant pathogens is not clear. Here, we describe that sRNAs of the pathogen
, which represents the kingdom of oomycetes and is phylogenetically distant from fungi, employ the host plant's Argonaute (AGO)/RNA-induced silencing complex for virulence. To demonstrate
sRNA (
sRNA) functionality in ck-RNAi, we designed a novel CRISPR endoribonuclease Csy4/GUS reporter that enabled in situ visualization of
sRNA-induced target suppression in Arabidopsis. The significant role of
sRNAs together with
AGO1 in virulence was revealed in plant
mutants and by transgenic Arabidopsis expressing a short-tandem-target-mimic to block
sRNAs, that both exhibited enhanced resistance.
sRNA-targeted plant genes contributed to host immunity, as Arabidopsis gene knockout mutants displayed quantitatively enhanced susceptibility.
Small ROP (also called RAC) GTPases are key factors in polar cell development and in interaction with the environment. ROP-Interactive Partner (RIP) proteins are predicted scaffold or ROP-effector ...proteins, which function downstream of activated GTP-loaded ROP proteins in establishing membrane heterogeneity and cellular organization. Grass ROP proteins function in cell polarity, resistance and susceptibility to fungal pathogens but grass RIP proteins are little understood.
We found that the barley (Hordeum vulgare L.) RIPa protein can interact with barley ROPs in yeast. Fluorescent-tagged RIPa, when co-expressed with the constitutively activated ROP protein CA RAC1, accumulates at the cell periphery or plasma membrane. Additionally, RIPa, locates into membrane domains, which are laterally restricted by microtubules when co-expressed with RAC1 and MICROTUBULE-ASSOCIATED ROP-GTPASE ACTIVATING PROTEIN 1. Both structural integrity of MICROTUBULE-ASSOCIATED ROP-GTPASE ACTIVATING PROTEIN 1 and microtubule stability are key to maintenance of RIPa-labeled membrane domains. In this context, RIPa also accumulates at the interface of barley and invading hyphae of the powdery mildew fungus Blumeria graminis f.sp. hordei.
Data suggest that barley RIPa interacts with barley ROPs and specifies RAC1 activity-associated membrane domains with potential signaling capacity. Lateral diffusion of this RAC1 signaling capacity is spatially restricted and the resulting membrane heterogeneity requires intact microtubules and MICROTUBULE-ASSOCIATED ROP-GTPASE ACTIVATING PROTEIN 1. Focal accumulation of RIPa at sites of fungal attack may indicate locally restricted ROP activity at sites of fungal invasion.
Plant pathogens such as Phytophthora infestans that caused the Irish Potato Famine continue to threaten local and global food security. Genetic and chemical plant protection measures are often ...overcome by adaptation of pathogen population structures. Therefore, there is a constant demand for new, consumer- and environment-friendly plant protection strategies. Metabolic alterations induced by P. infestans in the foliage and tubers of six different potato cultivars were investigated. Using a combination of untargeted metabolomics, isolation techniques, and structure elucidation by MS and 1D/2D-NMR experiments, five steroidal glycoalkaloids, five oxylipins, and four steroidal saponins were identified. As the steroidal saponins showed antioomycete but no hemolytic activity, they may thus be considered as probably safe target substances for enrichment in breeding programs for disease resistance and as chemical lead structures for the production of nature-derived synthetic antioomycetes.
Fate of Fusarium Toxins during the Malting Process Habler, Katharina; Hofer, Katharina; Geißinger, Cajetan ...
Journal of agricultural and food chemistry,
02/2016, Volume:
64, Issue:
6
Journal Article
Peer reviewed
Little is known about the fate of Fusarium mycotoxins during the barley malting process. To determine the fungal DNA and mycotoxin concentrations during malting, we used barley grain harvested from ...field plots that we had inoculated with Fusarium species that produce type A or type B trichothecenes or enniatins. Using a recently developed multimycotoxin liquid chromatography–tandem mass stable isotope dilution method, we identified Fusarium-species-specific behaviors of mycotoxins in grain and malt extracts and compared toxin concentrations to amounts of fungal DNA in the same samples. In particular, the type B trichothecenes and Fusarium culmorum DNA contents were increased dramatically up to 5400% after kilning. By contrast, the concentrations of type A trichothecenes and Fusarium sporotrichioides DNA decreased during the malting process. These data suggest that specific Fusarium species that contaminate the raw grain material might have different impacts on malt quality.
Plant RBOH (RESPIRATORY BURST OXIDASE HOMOLOGS)-type NADPH oxidases produce superoxide radical anions and have a function in developmental processes and in response to environmental challenges. ...Barley RBOHF2 has diverse reported functions in interaction with the biotrophic powdery mildew fungus Blumeria graminis f. sp. hordei. Here, we analyzed, in detail, plant leaf level- and age-specific susceptibility of stably RBOHF2-silenced barley plants. This revealed enhanced susceptibility to fungal penetration of young RBOHF2-silenced leaf tissue but strongly reduced susceptibility of older leaves when compared with controls. Loss of susceptibility in old RBOHF2-silenced leaves was associated with spontaneous leaf-tip necrosis and constitutively elevated levels of free and conjugated salicylic acid. Additionally, these leaves more strongly expressed pathogenesis-related genes, both constitutively and during interaction with B. graminis f. sp. hordei. Together, this supports the idea that barley RBOHF2 contributes to basal resistance to powdery mildew infection in young leaf tissue but is required to control leaf cell death, salicylic acid accumulation, and defense gene expression in older leaves, explaining leaf age-specific resistance of RBOHF2-silenced barley plants.
Fungi of the recently defined order Sebacinales (Basidiomycota) are involved in a wide spectrum of mutualistic symbioses (including mycorrhizae) with various plants, thereby exhibiting a unique ...potential for biocontrol strategies. The axenically cultivable root endophyte Piriformospora indica is a model organism of this fungal order. It is able to increase biomass and grain yield of crop plants. In barley, the endophyte induces local and systemic resistance to fungal diseases and to abiotic stress. To elucidate the lifestyle of P. indica, we analyzed its symbiotic interaction and endophytic development in barley roots. We found that fungal colonization increases with root tissue maturation. The root tip meristem showed no colonization, and the elongation zone showed mainly intercellular colonization. In contrast, the differentiation zone was heavily infested by inter- and intracellular hyphae and intracellular chlamydospores. The majority of hyphae were present in dead rhizodermal and cortical cells that became completely filled with chlamydospores. In some cases, hyphae penetrated cells and built a meshwork around plasmolyzed protoplasts, suggesting that the fungus either actively kills cells or senses cells undergoing endogenous programmed cell death. Seven days after inoculation, expression of barley BAX inhibitor-1 (HvBI-1), a gene capable of inhibiting plant cell death, was attenuated. Consistently, fungal proliferation was strongly inhibited in transgenic barley overexpressing GFP-tagged HvBI-1, which shows that P. indica requires host cell death for proliferation in differentiated barley roots. We suggest that the endophyte interferes with the host cell death program to form a mutualistic interaction with plants.
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