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Influence of light availability and soil productivity on insect herbivory on bilberry (Vaccinium myrtillus L.) leaves following mammalian herbivory.

ABSTRACT: Vegetative parts of bilberry (Vaccinium myrtillus) are important forage for many boreal forest mammal, bird and insect species. Plant palatability to insects is affected by concentration of nutrients and defense compounds in plants. We expected that palatability of bilberry leaves to insect herbivores is influenced by light availability and soil productivity (both affecting nitrogen concentration and constitutive carbon-based defense compound concentration) and herbivory by mammals (affecting nitrogen concentration and induced carbon-based defense compound concentration). We studied bilberry leaf herbivory under different light availability, soil productivity and mammalian herbivory pressure in small sampling units (1m x 1m) in boreal forest in Norway. We used generalized linear mixed models and generalized additive mixed models to model insect herbivory on bilberry leaves as a function of shade, soil productivity and mammalian herbivory. Observed insect herbivory on bilberry leaves increased with increasing shade levels. Predicted insect herbivory increased with increasing previous mammalian herbivory at high shade levels and this response was magnified at higher soil productivity levels. At low to intermediate shade levels, this response was only present under high soil productivity levels. Our results indicate that light availability is more important for variation in bilberry leaf palatability than soil nutrient conditions.

SUBMITTER: Schrijvers-Gonlag M

PROVIDER: S-EPMC7100976 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Influence of light availability and soil productivity on insect herbivory on bilberry (Vaccinium myrtillus L.) leaves following mammalian herbivory.

Schrijvers-Gonlag Marcel M Skarpe Christina C Andreassen Harry Peter HP

PloS one 20200327 3

Vegetative parts of bilberry (Vaccinium myrtillus) are important forage for many boreal forest mammal, bird and insect species. Plant palatability to insects is affected by concentration of nutrients and defense compounds in plants. We expected that palatability of bilberry leaves to insect herbivores is influenced by light availability and soil productivity (both affecting nitrogen concentration and constitutive carbon-based defense compound concentration) and herbivory by mammals (affecting ni ...[more]

PMID: 32218604

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Project description:BACKGROUND:Bilberry (Vaccinium myrtillus L.) is one of the most abundant wild berries in the Northern European ecosystems. This species plays an important ecological role as a food source for many vertebrate and invertebrate herbivores. It is also well-recognized for its bioactive compounds, particularly substances involved in natural defenses against herbivory. These defenses are known to be initiated by leaf damage (e.g. chewing by insects) and mediated by activation of the jasmonic acid (JA) signaling pathway. This pathway can be activated by exogenous application of methyl jasmonate (MeJA), the volatile derivative of JA, which is often used to stimulate plant defense responses in studies of plant-herbivore interactions at ecological, biochemical, and molecular organismal levels. As a proxy for herbivore damage, wild V. myrtillus plants were treated in the field with MeJA and changes in gene expression were compared to untreated plants. RESULTS:The de novo transcriptome assembly consisted of 231,887 unigenes. Nearly 71% of the unigenes were annotated in at least one of the databases interrogated. Differentially expressed genes (DEGs), between MeJA-treated and untreated control bilberry plants were identified using DESeq. A total of 3590 DEGs were identified between the treated and control plants, with 2013 DEGs upregulated and 1577 downregulated. The majority of the DEGs identified were associated with primary and secondary metabolism pathways in plants. DEGs associated with growth (e.g. those encoding photosynthesis-related components) and reproduction (e.g. flowering control genes) were frequently down-regulated while those associated with defense (e.g. encoding enzymes involved in biosynthesis of flavonoids, lignin compounds, and deterrent/repellent volatile organic compounds) were up-regulated in the MeJA treated plants. CONCLUSIONS:Ecological studies are often limited by controlled conditions to reduce the impact of environmental effects. The results from this study support the hypothesis that bilberry plants, growing in natural conditions, shift resources from growth and reproduction to defenses while in a MeJA-induced state, as when under insect attack. This study highlights the occurrence of this trade-off at the transcriptional level in a realistic field scenario and supports published field observations wherein plant growth is retarded and defenses are upregulated.

Project description:BackgroundCarotenoids are important pigments and precursors for central signaling molecules associated in fruit development and ripening. Carotenoid metabolism has been studied especially in the climacteric tomato fruit but the content of carotenoids and the regulation of their metabolism have been shown to be highly variable between fruit species. Non-climacteric berries of the genus Vaccinium are among the best natural sources of health-beneficial flavonoids but not studied previously for carotenoid biosynthesis.ResultsIn this study, carotenoid biosynthetic genes, PSY, PDS, ZDS, CRTISO, LCYB, LCYE, BCH and CYP450-BCH, as well as a carotenoid cleavage dioxygenase CCD1 were identified from bilberry (V. myrtillus L.) fruit and their expression was studied along with carotenoid composition during fruit development under different photoperiod and light quality conditions. Bilberry was found to be a good source of carotenoids among fruits and berries. The most abundant carotenoids throughout the berry development were lutein and β-carotene, which were accompanied by lower amounts of 9Z-β-carotene, violaxanthin, neoxanthin, zeaxanthin, antheraxanthin and β-cryptoxanthin. The expression patterns of the biosynthetic genes in ripening fruits indicated a metabolic flux towards β-branch of the carotenoid pathway. However, the carotenoid levels decreased in both the β-branch and ε,β-branch towards bilberry fruit ripening along with increased VmCCD1 expression, similarly to VmNCED1, indicating enzymatic carotenoid cleavage and degradation. Intense white light conditions increased the expression of the carotenoid biosynthetic genes but also the expression of the cleavage genes VmCCD1 and VmNCED1, especially in unripe fruits. Instead, mature bilberry fruits responded specifically to red/far-red light wavelengths by inducing the expression of both the carotenoid biosynthetic and the cleavage genes indicating tissue and developmental stage specific regulation of apocarotenoid formation by light quality.ConclusionsThis is the first report of carotenoid biosynthesis in Vaccinium berries. Our results indicate that both transcriptional regulation of the key biosynthetic genes and the enzymatic degradation of the produced carotenoids to apocarotenoids have significant roles in the determination of the carotenoid content and have overall effect on the metabolism during the bilberry fruit ripening.

Project description:Ripening of non-climacteric bilberry (Vaccinium myrtillus L.) fruit is characterized by a high accumulation of health-beneficial anthocyanins. Plant hormone abscisic acid (ABA) and sucrose have been shown to be among the central signaling molecules coordinating non-climacteric fruit ripening and anthocyanin accumulation in some fruits such as strawberry. Our earlier studies have demonstrated an elevation in endogenous ABA level in bilberry fruit at the onset of ripening indicating a role for ABA in the regulation of bilberry fruit ripening. In the present study, we show that the treatment of unripe green bilberry fruits with exogenous ABA significantly promotes anthocyanin biosynthesis and accumulation both in fruits attached and detached to the plant. In addition, ABA biosynthesis inhibitor, fluridone, delayed anthocyanin accumulation in bilberries. Exogenous ABA also induced the expression of several genes involved in cell wall modification in ripening bilberry fruits. Furthermore, silencing of VmNCED1, the key gene in ABA biosynthesis, was accompanied by the down-regulation in the expression of key anthocyanin biosynthetic genes. In contrast, the treatment of unripe green bilberry fruits with exogenous sucrose or glucose did not lead to an enhancement in the anthocyanin accumulation neither in fruits attached to plant nor in post-harvest fruits. Moreover, sugars failed to induce the expression of genes associated in anthocyanin biosynthesis or ABA biosynthesis while could elevate expression of some genes associated with cell wall modification in post-harvest bilberry fruits. Our results demonstrate that ABA plays a major role in the regulation of ripening-related processes such as anthocyanin biosynthesis and cell wall modification in bilberry fruit, whereas sugars seem to have minor regulatory roles in the processes. The results indicate that the regulation of bilberry fruit ripening differs from strawberry that is currently considered as a model of non-climacteric fruit ripening. In this study, we also identified transcription factors, which expression was enhanced by ABA, as potential regulators of ABA-mediated bilberry fruit ripening processes.

Dataset Information

Influence of light availability and soil productivity on insect herbivory on bilberry (Vaccinium myrtillus L.) leaves following mammalian herbivory.

Publications

Influence of light availability and soil productivity on insect herbivory on bilberry (Vaccinium myrtillus L.) leaves following mammalian herbivory.

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