Isoprene: An Antioxidant Itself or a Molecule with Multiple Regulatory Functions in Plants?
Abstract
:1. Isoprene: Some Generalities
2. Isoprene Protection from Abiotic Stress
3. Isoprene Modulation of Genomic, Proteomic and Metabolomic Profiles
4. Isoprene as Hormone Regulating Plant Antioxidant System and Growth
5. Isoprene as Defense Priming Molecule: Emerging Clues
6. Conclusions
Author Contributions
Funding
Conflicts of Interest
References
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Isoprene Effect | Plant | Genes, Proteins, Metabolites Influenced by Isoprene | Condition | Reference |
---|---|---|---|---|
Genes | ||||
Up-regulated | Poplar (WT and Knock-out) | Biosynthetic pathways of condensed tannins, anthocyanins and phenylpropanoids, and regulatory pathways of phenylpropanoids genes. | high light and heat stress | [50] |
Up- and down-regulated | Arabidopsis and tobacco (WT and IspS). Arabidopsis (WT) fumigated with isoprene | Abiotic and biotic stress defence, growth regulator signaling pathways, photosynthesis, seed germination, and seedling and plant growth, JA mediated defense signaling, phenylpropanoid biosynthesis and regulation, and cytokinins (CK)-mediated wound repair genes. | non-stressful conditions | [51] |
Up-regulated | Arabidopsis (WT) fumigated with isoprene | Chloroplast, phenylpropanoid biosynthetic and translation machinery genes, transcription factor-enriched gene network | non-stressful conditions | [52] |
Up-regulated | Arabidopsis (WT and IspS) | RD29B gene (abscisic acid-activated signaling pathway) | exogenous ABA supplement | [53] |
Down-regulated | Arabidopsis (WT and IspS) | COR15A gene (stromal proteins protection), and P5CS (reactive oxidative species protection) | water-stress | [53] |
Proteins | ||||
Higher concentrations | Poplar (WT and Knockout) | Chloroplast proteins involved in photosynthesis, light reactions, redox regulation, and oxidative stress defense and general metabolism | Control | [55] |
Higher concentrations | Poplar (WT and Knockout) | Proteins involved in phenylpropanoid pathway and flavonoid biosynthesis | Control | [56] |
Lower concentrations | Poplar (WT and Knockout) | Proteins involved in the biosynthesis of terpenoids, carotenoids and in the methylerythritol phosphate (MEP) and jasmonic acid pathways | Control | [56] |
Metabolites | ||||
Higher concentrations | Poplar (WT and Knockout) | Total phenolics and condensed tannins | high light and heat stress | [50] |
Similar concentrations | Poplar (WT and Knockout) | Photosynthetic pigments and secondary metabolites | high light and heat stress | [50] |
Higher concentrations | Arabidopsis and tobacco (WT and IspS) | Chlorophylls and carotenoids | non-stressful conditions | [51] |
Higher concentrations | Poplar (WT and Knockout) | Chlorophylls, carotenes and xanthophylls | light and dark conditions | [57] |
Higher concentrations | Poplar (WT and Knockout) | Chlorophyll content | Control | [50,58] |
Similar concentrations | Poplar (WT and Knockout) | Carotenoids | Control | [50,58] |
Lower concentrations | Poplar (WT and Knockout) | Zeaxanthin | Heat | [59] |
Higher concentrations | Tobacco (WT and IspS) | Zeaxanthin, anteraxanthin and phenylpropanoids | drought conditions | [60] |
Higher concentrations | Poplar (WT and Knockout) | Monogalactosyldiacylglycerols, digalactosyldiacylglycerols, phospholipids and unsaturated fatty acids | Control | [61] |
Isoprene Role | Functional Expectations | Experimental Evidence |
---|---|---|
Antioxidant | Protection against oxidative damage by direct reaction with oxidizing molecules (ROS or NO) | PRO: Isoprene contributes to thermal and oxidative stress tolerance by quenching ROS and reactive nitrogen species [36,39]. CON: Secondary antioxidants generated by reaction with ROS (e.g., methyl vinyl ketone) being per se cytotoxic may be removed without isoprene quenching [14]. Insufficient isopreneconcentration inside membranes to carry out effective antioxidant action [17]. |
Membrane protection | Stabilization of membrane properties when challenged by stresses by intercalating membrane lipids | PRO: Isoprene lipophylic nature favors isoprene presence in thylakoidal membranes which are kept elastic and fluid at rising temperature [29]. CON: Isoprene concentration in the membranes theoretically very low [17]. |
Defense priming stimulus | Improving stress resistance/tolerance by boosting stress signal perception, propagation, and/or activation of defense mechanisms. A quicker/stronger defense gene expression during and not before stress conditions is the hallmark of priming. | PRO: Isoprene-emitting transgenic lines show enhanced tolerance to dehydration and heat stress by displaying enhanced ABA-induced stomatal closure, reduced water loss, and higher ABA-induced expression of the ABA-responsive marker gene RD29B [53]. Isoprene exposure induces resistance to bacterial infection through SA-dependent defense mechanisms in Arabidopsis [74]. Isoprene fumigation induces a small reprogramming of the transcriptome (167 DEGs, fold change >2) in Arabidopsis, including up-regulation of some of the most important defensive pathway genes [52]. CON: ROS levels are reduced during thermal and oxidative stress because of direct and rapid antioxidant action of isoprene [36], without any need to invoke priming. Unclear whether isoprene-exposed plants (e.g., Arabidopsis in [74]) are more resistant to bacterial infection because of isoprene induction of SA synthesis and activation of SA-dependent defenses ahead of infection (no priming) or because isoprene also primes SA-dependent defenses for a more robust defensive behavior upon infection. |
Stress signal | Increased production after stress and role as transmission signal of stresses to other parts of the plant and/or to neighboring plants | PRO: Isoprene emission changes rapidly in response to wounding and temperature [75]. Knocking-down (by RNAi) or inhibiting (by fosmidomycin) isoprene emission negatively impacts thermotolerance [30,33,59]. CON: Isoprene production occurs constitutively in several plants without apparent association to environmental stress [22]. Isps gene promoter activity takes place in roots and especially in developing lateral roots [65] during normal growth. Isoprene-emitting transgenic lines show positive effects on growth and development in unstressed plants [51]. |
Hormone | Regulation, at very low concentration, of plant processes at the gene level | PRO: Isoprene acts as a negative regulator of ROS production by modulating gene expression [51,58,65,66]. Isoprene can both positively and negatively regulate plant growth and development [51,65]. CON: Isoprene is produced and emitted in very large amount by plants [22] which does not make it a hormone by definition. |
Infochemical | Attraction of pollinators and insect predators or repulsion of phytophagous insects | PRO: Isoprene is a highly volatile molecule as are many infochemicals [76]. Tobacco plants emitting isoprene repel Manduca sexta larvae [77]. The parasitic wasp Diadegma semiclausum perceives isoprene by its chemoreceptors and is being repelled [31]. CON: Chrysomela populi (poplar leaf beetle) is unable to detect isoprene and show no preference for isoprene-emitting or non-emitting poplar plants [78,79]. Isoprene production occurs constitutively in several plants without apparent association to delivery of infochemical messages [22]. |
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Pollastri, S.; Baccelli, I.; Loreto, F. Isoprene: An Antioxidant Itself or a Molecule with Multiple Regulatory Functions in Plants? Antioxidants 2021, 10, 684. https://doi.org/10.3390/antiox10050684
Pollastri S, Baccelli I, Loreto F. Isoprene: An Antioxidant Itself or a Molecule with Multiple Regulatory Functions in Plants? Antioxidants. 2021; 10(5):684. https://doi.org/10.3390/antiox10050684
Chicago/Turabian StylePollastri, Susanna, Ivan Baccelli, and Francesco Loreto. 2021. "Isoprene: An Antioxidant Itself or a Molecule with Multiple Regulatory Functions in Plants?" Antioxidants 10, no. 5: 684. https://doi.org/10.3390/antiox10050684
APA StylePollastri, S., Baccelli, I., & Loreto, F. (2021). Isoprene: An Antioxidant Itself or a Molecule with Multiple Regulatory Functions in Plants? Antioxidants, 10(5), 684. https://doi.org/10.3390/antiox10050684