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Publikation

Schubert, R.; Werner, S.; Cirka, H.; Rödel, P.; Tandron Moya, Y.; Mock, H.-P.; Hutter, I.; Kunze, G.; Hause, B.; Effects of Arbuscular Mycorrhization on fruit quality in industrialized tomato production Int. J. Mol. Sci. 21, 7029, (2020) DOI: 10.3390/ijms21197029

Industrialized tomato production faces a decrease in flavors and nutritional value due to conventional breeding. Moreover, tomato production heavily relies on nitrogen and phosphate fertilization. Phosphate uptake and improvement of fruit quality by arbuscular mycorrhizal (AM) fungi are well-studied. We addressed the question of whether commercially used tomato cultivars grown in a hydroponic system can be mycorrhizal, leading to improved fruit quality. Tomato plants inoculated with Rhizophagus irregularis were grown under different phosphate concentrations and in substrates used in industrial tomato production. Changes in fruit gene expression and metabolite levels were checked by RNAseq and metabolite determination, respectively. The tests revealed that reduction of phosphate to 80% and use of mixed substrate allow AM establishment without affecting yield. By comparing green fruits from non-mycorrhizal and mycorrhizal plants, differentially expressed genes (DEGs) were found to possibly be involved in processes regulating fruit maturation and nutrition. Red fruits from mycorrhizal plants showed a trend of higher BRIX values and increased levels of carotenoids in comparison to those from non-mycorrhizal plants. Free amino acids exhibited up to four times higher levels in red fruits due to AM, showing the potential of mycorrhization to increase the nutritional value of tomatoes in industrialized production.
Publikation

Kusstatscher, P.; Wicaksono, W. A.; Bergna, A.; Cernava, T.; Bergau, N.; Tissier, A.; Hause, B.; Berg, G.; Trichomes form genotype-specific microbial hotspots in the phyllosphere of tomato Environ. Microbiome 15, 17, (2020) DOI: 10.1186/s40793-020-00364-9

Background: The plant phyllosphere is a well-studied habitat characterized by low nutrient availability and high community dynamics. In contrast, plant trichomes, known for their production of a large number of metabolites, are a yet unexplored habitat for microbes. We analyzed the phyllosphere as well as trichomes of two tomato genotypes (Solanum lycopersicum LA4024, S. habrochaites LA1777) by targeting bacterial 16S rRNA gene fragments. Results: Leaves, leaves without trichomes, and trichomes alone harbored similar abundances of bacteria (108–109 16S rRNA gene copy numbers per gram of sample). In contrast, bacterial diversity was found significantly increased in trichome samples (Shannon index: 4.4 vs. 2.5). Moreover, the community composition was significantly different when assessed with beta diversity analysis and corresponding statistical tests. At the bacterial class level, Alphaproteobacteria (23.6%) were significantly increased, whereas Bacilli (8.6%) were decreased in trichomes. The bacterial family Sphingomonadacea (8.4%) was identified as the most prominent, trichome-specific feature; Burkholderiaceae and Actinobacteriaceae showed similar patterns. Moreover, Sphingomonas was identified as a central element in the core microbiome of trichome samples, while distinct low-abundant bacterial families including Hymenobacteraceae and Alicyclobacillaceae were exclusively found in trichome samples. Niche preferences were statistically significant for both genotypes and genotype-specific enrichments were further observed. Conclusion: Our results provide first evidence of a highly specific trichome microbiome in tomato and show the importance of micro-niches for the structure of bacterial communities on leaves. These findings provide further clues for breeding, plant pathology and protection as well as so far unexplored natural pathogen defense strategies.
Publikation

El Amerany, F.; Meddich, A.; Wahbi, S.; Porzel, A.; Taourirte, M.; Rhazi, M.; Hause, B.; Foliar Application of Chitosan Increases Tomato Growth and Influences Mycorrhization and Expression of Endochitinase-Encoding Genes Int. J. Mol. Sci. 21, 535, (2020) DOI: 10.3390/ijms21020535

Nowadays, applying bio-organic fertilizer (e.g., chitosan, Ch) or integrating beneficial microorganisms (e.g., arbuscular mycorrhizal fungi, AMF) are among the successful strategies to promote plant growth. Here, the effect of two application modes of Ch (foliar spray or root treatment) and Ch-derived nanoparticles (NPs) on tomato plants colonized with the AMF Rhizophagus irregularis were analyzed, thereby focusing on plant biomass, flowering and mycorrhization. An increase of shoot biomass and flower number was observed in arbuscular mycorrhizal (AM) plants sprayed with Ch. The interaction with AMF, however, was reduced as shown by decreased mycorrhization rates and AM-specific gene expression. To get insights into Ch effect on mycorrhization, levels of sugars, jasmonates, abscisic acid, and the expression of two chitinase-encoding genes were determined in mycorrhizal roots. Ch had no effect on sugar and phytohormone levels, but the reduced mycorrhization was correlated with down- and upregulated expression of Chi3 and Chi9, respectively. In contrast, application of NPs to leaves and Ch applied to the soil did not show any effect, neither on mycorrhization rate nor on growth of mycorrhizal plants. Concluding, Ch application to leaves enhanced plant growth and flowering and reduced interaction with AMF, whereas root treatment did not affect these parameters.
Publikation

Asfaw, K. G.; Liu, Q.; Xu, X.; Manz, C.; Purper, S.; Eghbalian, R.; Münch, S. W.; Wehl, I.; Bräse, S.; Eiche, E.; Hause, B.; Bogeski, I.; Schepers, U.; Riemann, M.; Nick, P.; A mitochondria-targeted coenzyme Q peptoid induces superoxide dismutase and alleviates salinity stress in plant cells Sci. Rep. 10, 11563, (2020) DOI: 10.1038/s41598-020-68491-4

Salinity is a serious challenge to global agriculture and threatens human food security. Plant cells can respond to salt stress either by activation of adaptive responses, or by programmed cell death. The mechanisms deciding the respective response are far from understood, but seem to depend on the degree, to which mitochondria can maintain oxidative homeostasis. Using plant PeptoQ, a Trojan Peptoid, as vehicle, it is possible to transport a coenzyme Q10 (CoQ10) derivative into plant mitochondria. We show that salinity stress in tobacco BY-2 cells (Nicotiana tabacum L. cv Bright Yellow-2) can be mitigated by pretreatment with plant PeptoQ with respect to numerous aspects including proliferation, expansion, redox homeostasis, and programmed cell death. We tested the salinity response for transcripts from nine salt-stress related-genes representing different adaptive responses. While most did not show any significant response, the salt response of the transcription factor NtNAC, probably involved in mitochondrial retrograde signaling, was significantly modulated by the plant PeptoQ. Most strikingly, transcripts for the mitochondrial, Mn-dependent Superoxide Dismutase were rapidly and drastically upregulated in presence of the peptoid, and this response was disappearing in presence of salt. The same pattern, albeit at lower amplitude, was seen for the sodium exporter SOS1. The findings are discussed by a model, where plant PeptoQ modulates retrograde signalling to the nucleus leading to a strong expression of mitochondrial SOD, what renders mitochondria more resilient to perturbations of oxidative balance, such that cells escape salt induced cell death and remain viable.
Bücher und Buchkapitel

Hause, B.; Requena, N.; Detection of Arbuscular Mycorrhizal Fungal Gene Expression by In Situ Hybridization (Ferrol, N. & Lanfranco, L., eds.). Methods Mol. Biol. 2146, 185-196, (2020) ISBN: 978-1-0716-0603-2 DOI: 10.1007/978-1-0716-0603-2_14

The complexity of the obligate symbiotic interaction of arbuscular mycorrhizal (AM) fungi and their host roots requires sophisticated molecular methods. In particular, to capture the dynamic of the interaction, cell-specific methods for gene expression analysis are required. In situ hybridization is a technique that allows to determine the location of transcript accumulation within tissues, being of special interest for these fungi that cannot be genetically modified. The method requires proper fixation and embedding methods as well as specific probes for the hybridization allowing detection of specific transcripts. In this chapter, we present a method to prepare roots, which have established a symbiosis with an arbuscular mycorrhizal fungus for the detection of fungal transcripts. This includes chemical fixation, subsequent embedding in a suitable medium, sectioning and pretreatment of sections, the hybridization procedure itself, as well as the immunological detection of RNA-RNA hybrids.
Publikation

Hause, B.; Elevated CO2‐induced improvement of mycorrhization – which players lie in‐between? New Phytol. 224, 5-7, (2019) DOI: 10.1111/nph.16023

This article is a Commentary on Zhou et al. 224: 106–116.
Publikation

Dreher, D.; Baldermann, S.; Schreiner, M.; Hause, B.; An arbuscular mycorrhizal fungus and a root pathogen induce different volatiles emitted by Medicago truncatula roots J. Adv. Res. 19, 85-90, (2019) DOI: 10.1016/j.jare.2019.03.002

Plants are in permanent contact with various microorganisms and are always impacted by them. To better understand the first steps of a plant’s recognition of soil-borne microorganisms, the early release of volatile organic compounds (VOCs) emitted from roots of Medicago truncatula in response to the symbiont Rhizophagus irregularis or the pathogenic oomycete Aphanomyces euteiches was analysed. More than 90 compounds were released from roots as detected by an untargeted gas chromatography-mass spectrometry approach. Principal component analyses clearly distinguished untreated roots from roots treated with either R. irregularis or A. euteiches. Several VOCs were found to be emitted specifically in response to each of the microorganisms. Limonene was specifically emitted from wild-type roots after contact with R. irregularis spores but not from roots of the mycorrhiza-deficient mutant does not make infections3. The application of limonene to mycorrhizal roots, however, did not affect the mycorrhization rate. Inoculation of roots with A. euteiches zoospores resulted in the specific emission of several sesquiterpenes, such as nerolidol, viridiflorol and nerolidol-epoxyacetate but application of nerolidol to zoospores of A. euteiches did not affect their vitality. Therefore, plants discriminate between different microorganisms at early stages of their interaction and respond differently to the level of root-emitted volatiles.
Publikation

Yadav, H.; Dreher, D.; Athmer, B.; Porzel, A.; Gavrin, A.; Baldermann, S.; Tissier, A.; Hause, B.; Medicago TERPENE SYNTHASE 10 Is Involved in Defense Against an Oomycete Root Pathogen Plant Physiol. 180, 1598-1613, (2019) DOI: 10.1104/pp.19.00278

In nature, plants interact with numerous beneficial or pathogenic soil-borne microorganisms. Plants have developed various defense strategies to expel pathogenic microbes, some of which function soon after pathogen infection. We used Medicago truncatula and its oomycete pathogen Aphanomyces euteiches to elucidate early responses of the infected root. A. euteiches causes root rot disease in legumes and is a limiting factor in legume production. Transcript profiling of seedlings and adult plant roots inoculated with A. euteiches zoospores for 2 h revealed specific upregulation of a gene encoding a putative sesquiterpene synthase (M. truncatula TERPENE SYNTHASE 10 [MtTPS10]) in both developmental stages. MtTPS10 was specifically expressed in roots upon oomycete infection. Heterologous expression of MtTPS10 in yeast led to production of a blend of sesquiterpenes and sesquiterpene alcohols, with NMR identifying a major peak corresponding to himalachol. Moreover, plants carrying a tobacco (Nicotiana tabacum) retrotransposon Tnt1 insertion in MtTPS10 lacked the emission of sesquiterpenes upon A. euteiches infection, supporting the assumption that the identified gene encodes a multiproduct sesquiterpene synthase. Mttps10 plants and plants with reduced MtTPS10 transcript levels created by expression of an MtTPS10-artificial microRNA in roots were more susceptible to A. euteiches infection than were the corresponding wild-type plants and roots transformed with the empty vector, respectively. Sesquiterpenes produced by expression of MtTPS10 in yeast also inhibited mycelial growth and A. euteiches zoospore germination. These data suggest that sesquiterpene production in roots by MtTPS10 plays a previously unrecognized role in the defense response of M. truncatula against A. euteiches.
Publikation

Wasternack, C.; Hause, B.; The missing link in jasmonic acid biosynthesis Nat. Plants 5, 776-777, (2019) DOI: 10.1038/s41477-019-0492-y

Jasmonic acid biosynthesis starts in chloroplasts and is finalized in peroxisomes. The required export of a crucial intermediate out of the chloroplast is now shown to be mediated by a protein from the outer envelope called JASSY.
Publikation

Mittelberger, C.; Stellmach, H.; Hause, B.; Kerschbamer, C.; Schlink, K.; Letschka, T.; Janik, K.; A Novel Effector Protein of Apple Proliferation Phytoplasma Disrupts Cell Integrity of Nicotiana spp. Protoplasts Int. J. Mol. Sci. 20, 4613, (2019) DOI: 10.3390/ijms20184613

Effector proteins play an important role in the virulence of plant pathogens such as phytoplasma, which are the causative agents of hundreds of different plant diseases. The plant hosts comprise economically relevant crops such as apples (Malus × domestica), which can be infected by ‘Candidatus Phytoplasma mali’ (P. mali), a highly genetically dynamic plant pathogen. As the result of the genetic and functional analyses in this study, a new putative P. mali effector protein was revealed. The so-called “Protein in Malus Expressed 2” (PME2), which is expressed in apples during P. mali infection but not in the insect vector, shows regional genetic differences. In a heterologous expression assay using Nicotiana benthamiana and Nicotiana occidentalis mesophyll protoplasts, translocation of both PME2 variants in the cell nucleus was observed. Overexpression of the effector protein affected cell integrity in Nicotiana spp. protoplasts, indicating a potential role of this protein in pathogenic virulence. Interestingly, the two genetic variants of PME2 differ regarding their potential to manipulate cell integrity. However, the exact function of PME2 during disease manifestation and symptom development remains to be further elucidated. Aside from the first description of the function of a novel effector of P. mali, the results of this study underline the necessity for a more comprehensive description and understanding of the genetic diversity of P. mali as an indispensable basis for a functional understanding of apple proliferation disease.
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