The role of terpenoids in plant response to biotic stress

Biljke su neprestano izložene različitim negativnim utjecajima iz okoliša koji mogu dovesti od razvitka abiotičkog odnosno biotičkog stresa u biljkama. Biotički stres u biljkama razvija se djelovanjem organizama koji ih okružuju, a to su najčešće biljojedni kukci, bakterije, virusi, gljivice i okružujuće biljke. Kao odgovor na biotički stres, biljke su razvile brojne mehanizme obrane, u kojima uz ostale stanične komponente, ulogu imaju i sekundarni biljni metaboliti. Najbrojniji biljni sekundarni metaboliti su terpenoidi. Njihova brojnost i strukturna različitost omogućava im da obnašaju različite uloge. Brojne uloge hlapljivih i nehlapljivih terpenoida uključuju direktnu i indirektnu obranu od biljojeda i patogena, privlačenje prirodnih neprijatelja biljojeda, signalizaciju susjednim biljkama ili ostalim dijelovima iste biljke o napadu na biljku te obranu mehaničkim preprekama. Navedene uloge govore o djelovanju biljnih terpenoida, ali ne razjašnjavaju mehanizme kako molekule terpenoida djeluju na organizme kojima su njihovi signali namijenjeni i kako pojačati ili smanjiti te signale da djeluju na način koji odgovara primjeni u poljoprivrednoj ili farmaceutskoj industriji. Moguće je da će ta i mnoga druga pitanja biti odgovorena genetičkim i metaboličkim inženjerstvom iako danas još uvijek postoje nedostaci u korištenim metodama.Plants are organisms that are constantly exposed to different environmental factors which can lead to abiotic and biotic stress in plants. Biotic stress in plants is caused by organisms such as herbivores, bacteria, viruses, fungus and plants that live in their surroundings and affect their wellbeing. To eliminate or lower biotic stress, plans have developed multiple defense strategies in which secondary metabolites take part. The most abundant secondary metabolites are terpenoids, and their structural diversity enables them to have different roles in plants. Roles of volatile and non-volatile terpenoids in plants include direct and indirect defense from herbivores and pathogens, attraction of herbivores natural enemies, signalization to nearby plants or within the plant itself and first line of defense by structural barriers. The roles of terpenoids introduce questions about how do terpenoids act upon organisms that the signals are aimed for and how to make the signals stronger or weaker to make use of them in agriculture or pharmaceutical industry. It is possible that this and many other questions will be answered by genetic and metabolic engineering, however the methods are still imperfect and need to be fine-tuned

An integrated “omics” approach to unravel the impact of root symbionts on tomato direct and indirect defenses against insect herbivores

As sessile organisms, plants are constantly under attack by insect herbivores. To defend themselves, they have developed a broad array of direct and indirect defense mechanisms. Plants can also build mutualistic relationships with several microbes that are hosted in their rhizosphere. These microbes provide their hosts with essential services, such as improved mineral uptake, nitrogen fixation, growth promotion, and protection from pathogens and insect herbivores. Among these beneficial microbes, the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis and the plant growth-promoting fungus (PGPF) Trichoderma harzianum have been broadly studied. In the present doctoral study, tomato (Solanum lycopersicum) was used as a model plant to investigate the effect of R. irregularis and T. harzianum on modulating tomato’s direct and indirect defenses against insect herbivores. Overall, the study aims to explore the potential of using beneficial root fungi in protecting crop plants against insect herbivores. In this frame, a series of experiments, comprising transcriptomic and metabolomic approaches, was conducted aiming to illuminate aspects of plant-microbe-insect interactions that are less studied and contribute to the transformation of conventional to sustainable Agriculture. Conclusively, the results presented in this doctoral thesis indicate that the beneficial root fungi R. irregularis and T. harzianum mediate plant-insect interactions and can trigger important effects over the three trophic levels: namely the plant, its herbivores, and their natural enemies. Therefore, these findings reinforce the potential of beneficial root fungi to be used in Agriculture as a promising alternative tool to reduce the use of chemical insecticides, ensure crop productivity and food security, and protect human health as well as the environment

Terpenes of the Essential Oil from Ipomoea alba Leaf in Response to Herbivore and Mechanical Injuries

There is no doubt that the chemical composition of plants, including norvolatile and volatile compounds, is widely affected by abiotic and biotic stress. Plants are able to biosynthesize a variety of secondary metabolites against actions of natural enemies, such as herbivores, fungus, virus and bacteria. The present study revealed that the chemical compositions of leaf essential oils from Ipomoea alba underwent quantitative and qualitative alterations both when infested with the grasshopper Elaeochlora trilineata and mechanically damaged. Grasshopper attack and mechanical wounding induced the biosynthesis of nine volatile compounds in leaves of I. alba: cumene, α-ylangene, β-panasinsene, β-gurjunene aromadendrene, β-funebrene, spirolepechinene, cubenol and sclareolide. The amount of germacrene D (33.2% to 20.4%) decreased when the leaves were mechanically damaged; but when the leaves were attacked by a grasshopper, the germacrene D increased from 33.2% to 39.4%. The results showed that I. alba leaves clearly responded to abiotic and biotic stress and contribute to an understanding of plant responses to stress conditions

Effects of Arbuscular Mycorrhizal Fungi (AMF) on Growth and Herbivore Defenses in Sorghum Sudangrass (Sorghum X drummondii)

Chapter 2: In this chapter we have examined the role of trichomes in plant stress biology, reviewed the studies on herbivore X trichome interactions, and their role in plant defences. Ultimately, we have proposed new areas of research for future work. Chapter 3: In this chapter, we examined whether AMF has cascading effects on insect community dynamics through attraction/repulsion of beneficial and damaging insects using Sorghum-sudangrass (Sorghum x drummondii), either inoculated with commercial AMF mix or left as control in lab and field experiments. Our results suggest positive effects of AMF on plant growth, and a lower initial incidence of fall armyworm (Spodoptera frugiperda), a major herbivore on Sorghum in the region. Besides, AMF inoculated plants attracted significantly more beneficial insects (predators and parasitoids) and a lower number of damaging herbivores. Therefore, our data suggests that AMF can have implications for sustainable pest management strategies

Mycorrhizal symbiosis primes the accumulation of antiherbivore compounds and enhances herbivore mortality in tomato

Plant association with arbuscular mycorrhizal fungi (AMF) can increase their ability to overcome multiple stresses, but their impact on plant interactions with herbivorous insects is controversial. Here we show higher mortality of the leaf-chewer Spodoptera exigua when fed on tomato plants colonized by the AMF Funneliformis mosseae, evidencing mycorrhiza-induced resistance. In search of the underlying mechanisms, an untargeted metabolomic analysis through ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS) was performed. The results showed that mycorrhizal symbiosis had a very limited impact on the leaf metabolome in the absence of stress, but significantly modulated the response to herbivory in the damaged area. A cluster of over accumulated metabolites was identified in those leaflets damaged by S. exigua feeding in mycorrhizal plants, while unwounded distal leaflets responded similar to those from non-mycorrhizal plants. These primed-compounds were mostly related to alkaloids, fatty acid derivatives and phenylpropanoid-polyamine conjugates. The deleterious effect on larval survival of some of these compounds, including the alkaloid physostigmine, the fatty acid derivatives 4-oxododecanedioic acid and azelaic acid, was confirmed. Thus, our results evidence the impact of AMF on metabolic reprograming upon herbivory that leads to a primed accumulation of defensive compounds

The role of terpenoids in plant response to biotic stress

Biljke su neprestano izložene različitim negativnim utjecajima iz okoliša koji mogu dovesti od razvitka abiotičkog odnosno biotičkog stresa u biljkama. Biotički stres u biljkama razvija se djelovanjem organizama koji ih okružuju, a to su najčešće biljojedni kukci, bakterije, virusi, gljivice i okružujuće biljke. Kao odgovor na biotički stres, biljke su razvile brojne mehanizme obrane, u kojima uz ostale stanične komponente, ulogu imaju i sekundarni biljni metaboliti. Najbrojniji biljni sekundarni metaboliti su terpenoidi. Njihova brojnost i strukturna različitost omogućava im da obnašaju različite uloge. Brojne uloge hlapljivih i nehlapljivih terpenoida uključuju direktnu i indirektnu obranu od biljojeda i patogena, privlačenje prirodnih neprijatelja biljojeda, signalizaciju susjednim biljkama ili ostalim dijelovima iste biljke o napadu na biljku te obranu mehaničkim preprekama. Navedene uloge govore o djelovanju biljnih terpenoida, ali ne razjašnjavaju mehanizme kako molekule terpenoida djeluju na organizme kojima su njihovi signali namijenjeni i kako pojačati ili smanjiti te signale da djeluju na način koji odgovara primjeni u poljoprivrednoj ili farmaceutskoj industriji. Moguće je da će ta i mnoga druga pitanja biti odgovorena genetičkim i metaboličkim inženjerstvom iako danas još uvijek postoje nedostaci u korištenim metodama.Plants are organisms that are constantly exposed to different environmental factors which can lead to abiotic and biotic stress in plants. Biotic stress in plants is caused by organisms such as herbivores, bacteria, viruses, fungus and plants that live in their surroundings and affect their wellbeing. To eliminate or lower biotic stress, plans have developed multiple defense strategies in which secondary metabolites take part. The most abundant secondary metabolites are terpenoids, and their structural diversity enables them to have different roles in plants. Roles of volatile and non-volatile terpenoids in plants include direct and indirect defense from herbivores and pathogens, attraction of herbivores natural enemies, signalization to nearby plants or within the plant itself and first line of defense by structural barriers. The roles of terpenoids introduce questions about how do terpenoids act upon organisms that the signals are aimed for and how to make the signals stronger or weaker to make use of them in agriculture or pharmaceutical industry. It is possible that this and many other questions will be answered by genetic and metabolic engineering, however the methods are still imperfect and need to be fine-tuned

The role of terpenoids in plant response to biotic stress

Biljke su neprestano izložene različitim negativnim utjecajima iz okoliša koji mogu dovesti od razvitka abiotičkog odnosno biotičkog stresa u biljkama. Biotički stres u biljkama razvija se djelovanjem organizama koji ih okružuju, a to su najčešće biljojedni kukci, bakterije, virusi, gljivice i okružujuće biljke. Kao odgovor na biotički stres, biljke su razvile brojne mehanizme obrane, u kojima uz ostale stanične komponente, ulogu imaju i sekundarni biljni metaboliti. Najbrojniji biljni sekundarni metaboliti su terpenoidi. Njihova brojnost i strukturna različitost omogućava im da obnašaju različite uloge. Brojne uloge hlapljivih i nehlapljivih terpenoida uključuju direktnu i indirektnu obranu od biljojeda i patogena, privlačenje prirodnih neprijatelja biljojeda, signalizaciju susjednim biljkama ili ostalim dijelovima iste biljke o napadu na biljku te obranu mehaničkim preprekama. Navedene uloge govore o djelovanju biljnih terpenoida, ali ne razjašnjavaju mehanizme kako molekule terpenoida djeluju na organizme kojima su njihovi signali namijenjeni i kako pojačati ili smanjiti te signale da djeluju na način koji odgovara primjeni u poljoprivrednoj ili farmaceutskoj industriji. Moguće je da će ta i mnoga druga pitanja biti odgovorena genetičkim i metaboličkim inženjerstvom iako danas još uvijek postoje nedostaci u korištenim metodama.Plants are organisms that are constantly exposed to different environmental factors which can lead to abiotic and biotic stress in plants. Biotic stress in plants is caused by organisms such as herbivores, bacteria, viruses, fungus and plants that live in their surroundings and affect their wellbeing. To eliminate or lower biotic stress, plans have developed multiple defense strategies in which secondary metabolites take part. The most abundant secondary metabolites are terpenoids, and their structural diversity enables them to have different roles in plants. Roles of volatile and non-volatile terpenoids in plants include direct and indirect defense from herbivores and pathogens, attraction of herbivores natural enemies, signalization to nearby plants or within the plant itself and first line of defense by structural barriers. The roles of terpenoids introduce questions about how do terpenoids act upon organisms that the signals are aimed for and how to make the signals stronger or weaker to make use of them in agriculture or pharmaceutical industry. It is possible that this and many other questions will be answered by genetic and metabolic engineering, however the methods are still imperfect and need to be fine-tuned

Do changes in Lactuca sativa metabolic performance, induced by mycorrhizal symbionts and leaf UV-B irradiation, play a role towards tolerance to a polyphagous insect pest?

: The increased ultraviolet radiation (UV) due to the altered stratospheric ozone leads to multiple plant physiological and biochemical adaptations, likely affecting their interaction with other organisms, such as pests and pathogens. Arbuscular mycorrhizal fungi (AMF) and UV-B treatment can be used as eco-friendly techniques to protect crops from pests by activating plant mechanisms of resistance. In this study, we investigated plant (Lactuca sativa) response to UV-B exposure and Funneliformis mosseae (IMA1) inoculation as well as the role of a major insect pest, Spodoptera littoralis. Lettuce plants exposed to UV-B were heavier and taller than non-irradiated ones. A considerable enrichment in phenolic, flavonoid, anthocyanin, and carotenoid contents and antioxidant capacity, along with redder and more homogenous leaf color, were also observed in UV-B-treated but not in AMF-inoculated plants. Biometric and biochemical data did not differ between AMF and non-AMF plants. AMF-inoculated plants showed hyphae, arbuscules, vesicles, and spores in their roots. AMF colonization levels were not affected by UV-B irradiation. No changes in S. littoralis-feeding behavior towards treated and untreated plants were observed, suggesting the ability of this generalist herbivore to overcome the plant chemical defenses boosted by UV-B exposure. The results of this multi-factorial study shed light on how polyphagous insect pests can cope with multiple plant physiological and biochemical adaptations following biotic and abiotic preconditioning

Metabolomics and transcriptomics to decipher molecular mechanisms underlying ectomycorrhizal root colonization of an oak tree

Mycorrhizas are known to have a positive impact on plant growth and ability to resist major biotic and abiotic stresses. However, the metabolic alterations underlying mycorrhizal symbiosis are still understudied. By using metabolomics and transcriptomics approaches, cork oak roots colonized by the ectomycorrhizal fungus Pisolithus tinctorius were compared with non-colonized roots. Results show that compounds putatively corresponding to carbohydrates, organic acids, tannins, long-chain fatty acids and monoacylglycerols, were depleted in ectomycorrhizal cork oak colonized roots. Conversely, non-proteogenic amino acids, such as gamma-aminobutyric acid (GABA), and several putative defense-related compounds, including oxylipin-family compounds, terpenoids and B6 vitamers were induced in mycorrhizal roots. Transcriptomic analysis suggests the involvement of GABA in ectomycorrhizal symbiosis through increased synthesis and inhibition of degradation in mycorrhizal roots. Results from this global metabolomics analysis suggest decreases in root metabolites which are common components of exudates, and in compounds related to root external protective layers which could facilitate plant-fungal contact and enhance symbiosis. Root metabolic pathways involved in defense against stress were induced in ectomycorrhizal roots that could be involved in a plant mechanism to avoid uncontrolled growth of the fungal symbiont in the root apoplast. Several of the identified symbiosis-specific metabolites, such as GABA, may help to understand how ectomycorrhizal fungi such as P. tinctorius benefit their host plants.info:eu-repo/semantics/publishedVersio

Comparative Transcriptomics and Proteomics of Atractylodes lancea in Response to Endophytic Fungus Gilmaniella sp. AL12 Reveals Regulation in Plant Metabolism

The fungal endophyte Gilmaniella sp. AL12 can establish a beneficial association with the medicinal herb Atractylodes lancea, and improve plant growth and sesquiterpenoids accumulation, which is termed “double promotion.” Our previous studies have uncovered the underling primary mechanism based on some physiological evidences. However, a global understanding of gene or protein expression regulation in primary and secondary metabolism and related regulatory processes is still lacking. In this study, we employed transcriptomics and proteomics of Gilmaniella sp. AL12-inoculated and Gilmaniella sp. AL12-free plants to study the impact of endophyte inoculation at the transcriptional and translational levels. The results showed that plant genes involved in plant immunity and signaling were suppressed, similar to the plant response caused by some endophytic fungi and biotroph pathogen. The downregulated plant immunity may contribute to plant-endophyte beneficial interaction. Additionally, genes and proteins related to primary metabolism (carbon fixation, carbohydrate metabolism, and energy metabolism) tended to be upregulated after Gilmaniella sp. AL12 inoculation, which was consistent with our previous physiological evidences. And, Gilmaniella sp. AL12 upregulated genes involved in terpene skeleton biosynthesis, and upregulated genes annotated as β-farnesene synthase and β-caryophyllene synthase. Based on the above results, we proposed that endophyte-plant associations may improve production (biomass and sesquiterpenoids accumulation) by increasing the source (photosynthesis), expanding the sink (glycolysis and tricarboxylic acid cycle), and enhancing the metabolic flux (sesquiterpenoids biosynthesis pathway) in A. lancea. And, this study will help to further clarify plant-endophyte interactions