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Phenolic compounds are essential components of the defensive chemical arsenal of conifer trees. This chemically diverse group encompasses stilbenoids, flavonoids, isoflavonoids, proanthocyanidins and lignans. All of them are produced from the common precursors, CoA esters of the phenylpropanoids: p-coumaroyl-CoA, cinnamoyl-CoA, caffeoyl-CoA and feruloyl-CoA. Two classes of enzymes, stilbene synthases and chalcone synthases, play important roles in the biosynthesis of plant phenolics, such as the conversion of the phenylpropanoid-CoA esters into stilbenoids and flavonoids, respectively. In this study, we investigated the transcriptional responses of the Scots pine ( Pinus sylvestris) genes encoding stilbene and chalcone synthases to the infection by the fungal pathogen Heterobasidion annosum. The experiments were performed on pine seedlings and mature trees. Our results show that the stilbene synthase gene is strongly induced in both age groups, but the level of induction in adult trees varied considerably among individual trees. Systemic induction in needles and hypocotyl regions was documented in young seedlings following fungal inoculation in root region. Concurrent changes in the expression of the chalcone synthase gene in response to fungal infection were much less pronounced. Our data confirm previous observations on the differential regulation of these enzymes in Scots pine and emphasize the role of stilbene synthase in the induced response to fungal infection. [ABSTRACT FROM AUTHOR]

Gene expression levels of pathogenesis-related proteins ( PR1, PR3, PR5, PR8 and PR9), cell wall modification genes ( PAL and expansin), signal transduction genes ( ACC oxidase, AOC, MAPK) and a Myb transcription factor were compared in two Hevea brasiliensis budded clones ( RRIM612 and PR107) 5 weeks after wounding and artificial inoculation with the white rot fungus, Rigidoporus microporus. PR3 class I chitinase was upregulated in RRIM612 in response to the pathogen when compared with the wounded control. PR9 class IV peroxidase was highly upregulated in PR107. PR1 and PR8 were expressed more in wounded than in inoculated clones. Genes involved in ethylene and jasmonic acid signalling pathways and phenylalanine ammonia-lyase ( PAL) were upregulated almost equally in both clones. The Myb transcription factor was upregulated in RRIM612, while MAPK was upregulated in PR107 when compared to the wounded control. The predicted expansin-like protein was upregulated 40-fold in RRIM612 when compared to the wounded control. The results demonstrate the variability in defence responses in different clones and provide the first set of defence genes expression profiles in the host-pathogen interaction of the white rot disease of rubber trees. [ABSTRACT FROM AUTHOR]

Interaction of the necrotroph Fusarium avenaceum with seedling roots of Norway spruce was studied. The results showed that Norway spruce seedlings were susceptible to the pathogen but disease progression and severity was dependent on inoculum potential. Host recognition of the pathogen marked by hypersensitive browning reactions occurred late, thus making successful resistance to cellular damage impossible. Such host resistance responses were mostly in the form of lignification, accumulation of electron dense materials and papillae formation. [ABSTRACT FROM AUTHOR]

Vascular disintegration mainly of medulla rays of spruce roots is of major significance in root rot disease of spruce caused by H. annosum. Using seedling roots as an experimental model, the possible routes and initial host reactions preceding invasion of vascular tissues was investigated. Transmission electron microscopy showed that penetration through the endodermis was an obvious route but not without host resistance. Using antibodies against H. annosum hyphal materials, some labelling of vascular tissues remote from sites of fungal colonization suggest the release of fungal secretory products partly active in tissue disintegration. Similarly, intense labelling was also observed in severely colonized host tissues at late stages of infection. Strong labelling recorded at 3 d p.i. mainly on fungal hyphae and scant gold particles on invaded host tissues could imply that induction of host antifungal metabolites may have been a late event. A correlation was found between total antigenic material in root homogenates measured by ELISA, density of tissue labelling by immunocytochemistry and severity of disease symptoms. The importance of this in relation to diagnosis of biotic root rot diseases in the field is discussed. [ABSTRACT FROM AUTHOR]

Abstract Background Symbiotic ectomycorrhizal associations of fungi with forest trees play important and economically significant roles in the nutrition, growth and health of boreal forest trees, as well as in nutrient cycling. The ecology and physiology of ectomycorrhizal associations with Pinus sp are very well documented but very little is known about the molecular mechanisms behind these mutualistic interactions with gymnosperms as compared to angiosperms. Results Using a micro-array approach, the relative abundance of 2109 EST transcripts during interaction of Pinus sylvestris roots with the ectomycorrhizal fungus was profiled. The results reveal significant differential expression of a total of 236 ESTs, 96 transcripts differentially abundant after 1 day of physical contact with the fungus, 134 transcripts after 5 days and only 6 after 15 days at early stages of mantle formation on emerging lateral roots. A subset of cell wall modification and stress related genes was further assessed by quantitative reverse transcription PCR at late stages of mycorrhizal development coinciding with Hartig net formation. The results reveal down regulation of gene transcripts involved in general defence mechanism (e.g. antimicrobial peptide) as well as those involved in cell wall modification (e.g. glycine rich protein, xyloglucan endo transglycosylase). Conclusion This study constitutes the first attempt to characterize the transcriptome of the plant partner in the Pinus sylvestris – Laccaria bicolor model system. We identified 236 ESTs which are potentially important for molecular regulation of a functional symbiotic association in conifer host. The results highlight similarities with other studies based on angiosperm model systems, nevertheless some differences were found in the timing and spatial scale of gene regulation during ectomycorrhiza development in gymnosperms. The present study has identified a number of potentially important molecular events responsible for the initiation and regulation of biochemical, physiological and morphological changes during development of a fully functional symbiosis that are relevant for gymnosperm hosts.

High-quality RNA is required for accurate gene expression and transcriptome analysis. The current methods of RNA extraction from berry fruits are either time-consuming or expensive. To simplify the conventional phenol-chloroform based RNA extraction method, we modified the protocol with less steps as well as the removal of the use of phenol. In this protocol, the extraction buffer is composed of hexadecyltrimethyl ammonium bromide (CTAB), polyvinylpyrrolidone (PVP), and Dithiothreitol (DTT). The method facilitates efficient removal of polysaccharides and phenolic compounds from both fruit pulp and fruit peel. Additionally, the protocol is phenol-free and less toxic than traditional phenol-containing method. High-quality RNA, with RNA Integrity Number value > 8, isolated by this method is applicable for RNA sequencing and qPCR. Only 3-4 working hours are required for one batch of RNA isolation.•Our method replaces the use of phenol-chloroform with chloroform, making the extraction less toxic.•The bilberry friut RNA is of high-quality and purity with less time input., (© 2021 The Authors. Published by Elsevier B.V.)

Parasitism and saprotrophic wood decay are two fungal strategies fundamental for succession and nutrient cycling in forest ecosystems. An opportunity to assess the trade-off between these strategies is provided by the forest pathogen and wood decayer Heterobasidion annosum sensu lato. We report the annotated genome sequence and transcript profiling, as well as the quantitative trait loci mapping, of one member of the species complex: H. irregulare. Quantitative trait loci critical for pathogenicity, and rich in transposable elements, orphan and secreted genes, were identified. A wide range of cellulose-degrading enzymes are expressed during wood decay. By contrast, pathogenic interaction between H. irregulare and pine engages fewer carbohydrate-active enzymes, but involves an increase in pectinolytic enzymes, transcription modules for oxidative stress and secondary metabolite production. Our results show a trade-off in terms of constrained carbohydrate decomposition and membrane transport capacity during interaction with living hosts. Our findings establish that saprotrophic wood decay and necrotrophic parasitism involve two distinct, yet overlapping, processes., (© 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.)

Because of the close relatedness between three species of Heterobasidion annosum (P-type), Heterobasidion parviporum (S-type) and Heterobasidion abietinum (F-type), we investigated the possible use of arrays from one species for studies of gene expression in the other. Clones containing partial cDNAs from 94 identifiable genes expressed during spore germination and differentiation in H. parviporum were printed manually in six replications on nylon membranes. The membrane was hybridized with chemifluorescent labelled cDNA from actively growing mycelia of H. parviporum, H. annosum or H. abietinum, cultivated on a non-selective substrate. Product-moment correlation coefficient varied between 0.81 and 0.49. Due to the level of correlation, in the gene expression among the intersterility groups, we concluded that the cDNA array of one can be used to study gene expression in the others.

In this study, a comparative assessment was undertaken of nutritional factors that are likely to influence in vivo growth of the S and P-types of necrotrophic root rot fungus Heterobasidion annosum and of the damping off pathogen Fusarium avenaceum respectively. The results indicate that glucose and fructose but not cellobiose or sucrose supported growth of these fungi when used as sole carbon source. Particularly for P-types and F. avenaceum, however, the utilization of cellobiose and sucrose was considerably enhanced by several fold in the presence of ethanol. In addition, key plant cell wall phenolics (ferulic acid, caffeic acid, p-coumaric acid) at 0.025% inhibited growth of the test fungi. But this toxicity was reversed in the presence of exogenously added cell wall sugars (glucose, fructose, sucrose, cellobiose) except for the P-types where sucrose addition was apparently slightly effective. Similarly, ethanol whether alone or in combination with the phenolics was poorly utilized except for F. avenaceum. The importance of these results in understanding factors influencing growth and development during pathogenesis of the necrotrophs on their conifer hosts is discussed.