Biography

From an early age I have been curious about how and why thing work the way they do. I also found plants fascinating as they contribute so much to our lives: food, oxygen, shelter, medicines. I am particularly interested in plant secondary metabolism and how these metabolites contribute to plant defense, fruit flavor, adn human health. I enjoy studying biology at the transcriptomics, proteomics, and metabolomics levels to gain insight into how secondary metabolites are produced. My current work is looking at molecular mechanism behind defense priming in spruce. Expertise: plant defense, molecular biology, plant biochemistry, functional genomics

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Abstract

Bark beetles and their symbiotic bluestain fungi kill more trees than all other natural factors and cause great economic losses in Norway spruce and other conifers. The tree's natural defenses are the most important factor maintaining bark beetle-fungus complexes at low, endemic levels. Spraying Norway spruce trees with the plant hormone methyl jasmonate (MeJA) primes tree defenses without eliciting notable induced defenses, but enables the trees to respond much more quickly and strongly when challenged by bark beetles or fungi several weeks after treatment. This phenomenon, known as defense priming, is a form of acquired resistance that enables cost-effective and vigorous defense responses. In field experiments with 50-year-old clonal spruce trees terpene concentrations in the bark increased 60-fold within 24 h after mechanical wounding of MeJA primed trees, compared with a 13-fold increase in unprimed control trees. We also observed altered transcriptional patterns in primed trees using Illumina deep transcriptome sequencing. When wounded, primed trees launched vigorous induced defenses with significant differential regulation of gene transcripts, such as those involved in phenylpropanoid synthesis leading to lignification. Resistance-like genes, such as the NB-LRR coding genes, are also more rapidly induced in primed than in unprimed trees. Transcriptome results from primed but unwounded trees indicate an alteration in the state of the chromatin, resembling changes associated with the activity of the epigenetic machinery creating long-lasting epigenetic marks. We do not know yet how long the primed state is activated in Norway spruce, but our data so far indicate that it may last for at least 3 years.

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Abstract

Acetophenones are phenolic metabolites of plant species. A metabolic route for the biosynthesis and release of 2 defence‐related hydroxyacetophenones in white spruce (Picea glauca) was recently proposed to involve 3 phases: (a) biosynthesis of the acetophenone aglycons catalysed by a currently unknown set of enzymes, (b) formation and accumulation of the corresponding glycosides catalysed by a glucosyltransferase, and (c) release of the aglycons catalysed by a glucosylhydrolase (PgβGLU‐1). We tested if this biosynthetic model is conserved across Pinaceae and land plant species. We assayed and surveyed the literature and sequence databases for possible patterns of the presence of the acetophenone aglycons piceol and pungenol and their glucosides, as well as sequences and expression of Pgβglu‐1 orthologues. In the Pinaceae, the 3 phases of the biosynthetic model are present and differences in expression of Pgβglu‐1 gene orthologues explain some of the interspecific variation in hydroxyacetophenones. The phylogenetic signal in the metabolite phenotypes was low across species of 6 plant divisions. Putative orthologues of PgβGLU‐1 do not form a monophyletic group in species producing hydroxyacetophenones. The biosynthetic model for acetophenones appears to be conserved across Pinaceae, whereas convergent evolution has led to the production of acetophenone glucosides across land plants.

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Abstract

Plants are sessile organisms that lack a specialized immune system to cope with biotic and abiotic stress. Instead, plants have complex regulatory networks that determine the appropriate distribution of resources between the developmental and the defense programs. In the last years, epigenetic regulation of repeats and gene expression has evolved as an important player in the transcriptional regulation of stress‐related genes. Here, we review the current knowledge about how different stresses interact with different levels of epigenetic control of the genome. Moreover, we analyze the different examples of transgenerational epigenetic inheritance and connect them with the known features of genome epigenetic regulation. Although yet to be explored, the interplay between epigenetics and stress resistance seems to be a relevant and dynamic player of the interaction of plants with their environments.

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Abstract

Acetophenones are phenolic compounds involved in the resistance of white spruce (Picea glauca) against spruce budworm (Choristoneura fumiferiana), a major forest pest in North America. The acetophenones pungenol and piceol commonly accumulate in spruce foliage in the form of the corresponding glycosides, pungenin and picein. These glycosides appear to be inactive against the insect but can be cleaved by a spruce b-glucosidase, PgbGLU-1, which releases the active aglycons. The reverse glycosylation reaction was hypothesized to involve a family 1 UDP-sugar dependent glycosyltransferase (UGT) to facilitate acetophenone accumulation in the plant. Metabolite and transcriptome profiling over a developmental time course of white spruce bud burst and shoot growth revealed two UGTs, PgUGT5 and PgUGT5b, that glycosylate pungenol. Recombinant PgUGT5b enzyme produced mostly pungenin, while PgUGT5 produced mostly isopungenin. Both UGTs also were active in vitro on select flavonoids. However, the context of transcript and metabolite accumulation did not support a biological role in flavonoid metabolism but correlated with the formation of pungenin in growing shoots. Transcript levels of PgUGT5b were higher than those of PgUGT5 in needles across different genotypes of white spruce. These results support a role of PgUGT5b in the biosynthesis of the glycosylated acetophenone pungenin in white spruce.