Grape plants are susceptible to multiple pathogens and parasites and, in response to these biotic attacks, have developed induced systemic resistance (ISR) mechanisms that provide protection against the causes of stress. Previous studies showed that, among the defense strategies adopted by grapevine, there is the response to the chemical signals emitted by plants damaged by pests and these defense molecules can be transferred through the air in the form of volatile organic compounds (VOCs). Other researchers supported the hypothesis that plants can communicate through common mycorrhizal networks (CMN) that grow between the root of nearby plants. However, until now, studies focused on the transfer of signal molecules through hyphal anastomosis between herbaceous species and within forest communities but there is no experimental evidences showing that CMN can transfer defense signals even between plants of Vitis vinifera L. . This study therefore aims to evaluate whether the mycorrhiza Glomus iranicum var. tenuihypharum sp. Nova is able to connect two grape plants (cv. Glera) and translocate defense molecules between individuals damaged by the leafhoppers Erasmoneura vulnerata and the plants not directly infested connected to them. To answer this question, first of all, it was verified whether the arbuscular mycorrhiza, contained in the commercial product MycoUp® (Biogard), was able to colonize the root systems of the grape plants used in the experimental design and to allow, through the connection hyphal, exchange of signals between contiguous grapevines whose epigeal apparatus was inside a plastic cap to exclude the possibility that the defense signals were transmitted through air. The results showed that the colonization of root tissues by the fungus, in addition to increasing the length of the host's primary root, it can contribute to the induced systemic resistance (ISR) of the plant against biotic and, probably, abiotic adversities. The RT-qPCR assays, aimed at analyzing the intensity of expression of some genes of the secondary metabolism of the grapevine involved in the response to stress, highlighted that the mycorrhized plants were able to overexpress the defense genes belonging to the multigene families VvPAL and VvSTS. Once the colonization of the root systems of the grapevines had been validated, the analysis of the gene expression showed that, 13 days after the infestation with E. vulnerata, the adjacent plants not attacked by the insect and connected by mycorrhiza with the plants infected with leafhopper, showed an increase in resistance to stress thanks to the upregulation of the defense genes encoding the enzymes phenylalanine ammonia lyase (VvPAL), stilbene synthase (VvSTS), the transcription factors MYB-R2R3 (VvMYB) and pathogenesis-related proteins (VvPR), compared to grapevines not treated with mycorrhizae and phytophagous. These results were not confirmed by analyzing the expression of the same genes after 20 days from the treatment with leafhopper. These lead to the hypothesis that after a certain period of time there may be saturation of the signaling system between the plants. These results, which are entirely preliminary, require further and broader investigations to verify whether mycorrhizae, in addition to having a positive role in the development of the root system of the vine cuttings, can actually allow the transfer of information between interconnected plants through fungal hyphae and how these signals can play a role in the integrated protection of the vineyard against parasites and other agents of disease.
Le piante di vite sono suscettibili ad un'ampia gamma di agenti patogeni e parassiti ed in risposta a questi attacchi biotici hanno sviluppato dei sistemi di difesa indotta (ISR) che vengono espressi solo in presenza di agenti di malattia e di danno, fornendo così una protezione sistematica contro il potenziale organismo dannoso. Studi pregressi hanno dimostrato che tra le strategie preventive di difesa adottate dalla vite per superare efficientemente gli attacchi da parte dei fitofagi, c’è la risposta ai segnali chimici emessi dagli individui danneggiati che possono essere trasferiti attraverso il mezzo aereo sottoforma di composti volatili (VOCs). Alcuni ricercatori hanno inoltre sostenuto l’ipotesi che le piante possono comunicare tra loro anche mediante le reti comuni di micorrize (CMN; Common Mycorrhizal Networks) che si sviluppano tra gli apparati radicali di individui adiacenti. Tuttavia, fino ad ora, la ricerca si è concentrata sul trasferimento di molecole-segnale attraverso anastomosi ifali tra specie erbacee ed all’interno delle comunità forestali, ma non ci sono prove sperimentali che dimostrino che le CMN possano trasferire segnali di difesa anche tra piante di vite (Vitis vinifera L.). Questo lavoro di tesi si prefigge quindi di valutare se il fungo micorrizico Glomus iranicum var. tenuihypharum sp. Nova riesce a mettere in comunicazione due piante di vite cv. Glera traslocando segali biochimici di difesa tra individui danneggiati dall’apparato boccale di Erasmoneura vulnerata e le piante ad essi collegate, ma non direttamente infestate, per attivare in queste ultime meccanismi di difesa precoci contro il fitofago. Per rispondere a tale quesito, in primis, è stato verificato se il fungo micorrizico arbuscolare, contenuto nel prodotto commerciale MycoUp® (Biogard), fosse in grado di colonizzare gli apparati radicali delle piante di vite del disegno sperimentale e di permettere, attraverso le anastomosi ifali, lo scambio di molecole-segnale tra viti contigue il cui apparato epigeo era stato confinato all’interno di un cappuccio anti-insetto per escludere eventuali trasferimenti di segnale tramite il mezzo aereo attraverso i VOCs. I risultati hanno evidenziato che la colonizzazione dei tessuti radicali da parte del fungo, oltre ad incrementare la lunghezza della radice primaria dell’ospite, può contribuire ad aumentare la resistenza sistemica indotta (ISR) della pianta contro le avversità biotiche e, probabilmente, abiotiche. I saggi RT-qPCR, volti ad analizzare l’intensità di espressione di alcuni geni del metabolismo secondario della vite coinvolti nella risposta agli stress, hanno infatti messo in evidenza che le piante micorrizate sono state in grado di sovra-esprimere i geni di difesa appartenenti alle famiglie multigeniche VvPAL e VvSTS. Una volta validata l’avvenuta colonizzazione degli apparati radicali delle viti, le analisi di espressione genica hanno messo in evidenza che, a 13 giorni dall’infestazione con E. vulnerata, le piante adiacenti non attaccate dall’insetto e collegate mediante micorrize con le piante infettate dalla cicalina americana, hanno manifestato un aumento della resistenza allo stress grazie alla sovraregolazione dei geni di difesa codificanti per gli enzimi fenilalanina ammonio-liasi (VvPAL), stilbene sintasi (VvSTS), per i fattori di trascrizione MYB-R2R3 (VvMYB) e per le proteine correlate alla patogenesi (VvPR), rispetto alle viti non trattate né con le micorrize né con il fitofago. Questi dati non sono stati confermati analizzando l’espressione degli stessi geni dopo 20 giorni dal trattamento con la cicalina. Queste osservazioni portano ad ipotizzare che dopo un certo periodo di tempo possa esserci la saturazione del sistema di segnalazione tra le viti.
Le micorrize consentono la comunicazione tra piante di vite (Vitis vinifera L.)?
CORBANESE, CHIARA
2021/2022
Abstract
Grape plants are susceptible to multiple pathogens and parasites and, in response to these biotic attacks, have developed induced systemic resistance (ISR) mechanisms that provide protection against the causes of stress. Previous studies showed that, among the defense strategies adopted by grapevine, there is the response to the chemical signals emitted by plants damaged by pests and these defense molecules can be transferred through the air in the form of volatile organic compounds (VOCs). Other researchers supported the hypothesis that plants can communicate through common mycorrhizal networks (CMN) that grow between the root of nearby plants. However, until now, studies focused on the transfer of signal molecules through hyphal anastomosis between herbaceous species and within forest communities but there is no experimental evidences showing that CMN can transfer defense signals even between plants of Vitis vinifera L. . This study therefore aims to evaluate whether the mycorrhiza Glomus iranicum var. tenuihypharum sp. Nova is able to connect two grape plants (cv. Glera) and translocate defense molecules between individuals damaged by the leafhoppers Erasmoneura vulnerata and the plants not directly infested connected to them. To answer this question, first of all, it was verified whether the arbuscular mycorrhiza, contained in the commercial product MycoUp® (Biogard), was able to colonize the root systems of the grape plants used in the experimental design and to allow, through the connection hyphal, exchange of signals between contiguous grapevines whose epigeal apparatus was inside a plastic cap to exclude the possibility that the defense signals were transmitted through air. The results showed that the colonization of root tissues by the fungus, in addition to increasing the length of the host's primary root, it can contribute to the induced systemic resistance (ISR) of the plant against biotic and, probably, abiotic adversities. The RT-qPCR assays, aimed at analyzing the intensity of expression of some genes of the secondary metabolism of the grapevine involved in the response to stress, highlighted that the mycorrhized plants were able to overexpress the defense genes belonging to the multigene families VvPAL and VvSTS. Once the colonization of the root systems of the grapevines had been validated, the analysis of the gene expression showed that, 13 days after the infestation with E. vulnerata, the adjacent plants not attacked by the insect and connected by mycorrhiza with the plants infected with leafhopper, showed an increase in resistance to stress thanks to the upregulation of the defense genes encoding the enzymes phenylalanine ammonia lyase (VvPAL), stilbene synthase (VvSTS), the transcription factors MYB-R2R3 (VvMYB) and pathogenesis-related proteins (VvPR), compared to grapevines not treated with mycorrhizae and phytophagous. These results were not confirmed by analyzing the expression of the same genes after 20 days from the treatment with leafhopper. These lead to the hypothesis that after a certain period of time there may be saturation of the signaling system between the plants. These results, which are entirely preliminary, require further and broader investigations to verify whether mycorrhizae, in addition to having a positive role in the development of the root system of the vine cuttings, can actually allow the transfer of information between interconnected plants through fungal hyphae and how these signals can play a role in the integrated protection of the vineyard against parasites and other agents of disease.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/36739