L'induzione dell'abscissione dei frutticini di melo \ue8 caratterizzata da un aumento coordinato dei livelli di acido abscissico e della produzione di isoprene

Durante la fase induttiva del processo di abscissione dei frutticini di melo (Malus domestica L. Borkh) si attuano, a livello della cortex, profondi cambiamenti a livello trascrizionale e metabolico. Nel melo, sistema modello per lo studio dell\u2019abscissione dei frutti, \ue8 possibile indurre selettivamente la cascola di frutticini in posizione specifiche del corimbo, tramite l\u2019impiego di diradanti chimici, come la benziladenina e il metamitron, che agiscono amplificando il potenziale naturale di cascola. Nella presente ricerca \ue8 stato condotto uno studio metabolomico dei componenti volatili (VOCs) emessi dai frutticini abscindenti, consentendo di identificare l\u2019isoprene come marcatore precoce dell\u2019induzione dell\u2019abscissione. La produzione di questo volatile, associata alla stimolazione dell\u2019espressione di un gene specifico codificante una isoprene sintasi (ISPS) e mirata a disintossicare il frutto dai radicali liberi dell\u2019ossigeno (ROS) prodotti in questa fase, \ue8 fortemente correlata ai livelli di acido abscissico (ABA) prodotto a livello della cortex dei frutticini. I livelli di ABA aumentano transitoriamente durante l\u2019induzione dell\u2019abscissione e sono associati all\u2019induzione trascrizionale di un gene NCED (9-cis-epossicarotenoide diossigenasi) specifico. Secondo un modello ipotetico, l\u2019ABA potrebbe cooperare in maniera transitoria con altri ormoni e/o altri messaggeri secondari nella generazione di un segnale intra-frutto che porta all\u2019attivazione a valle della zona di abscissione. Il processo di separazione dei frutticini, quindi, sembra essere orchestrato da vie trasduttive multiple, la cui regolazione, esercitata entro una finestra temporale molto breve da stimoli endogeni e/o esogeni, determina il destino finale dei frutticini. In questo contesto, il ruolo della cortex come \u201csentinella\u201d del seme viene ancora una volta confermato. Questo studio \ue8 finanziato dal Progetto AGER, grant n\ub0 2010-2119

Early induction of apple fruitlet abscission is characterized by an increase of both isoprene emission and abscisic acid content

Apple (Malus domestica L. Borkh) fruitlet abscission represents an interesting model system to study the early phases of the shedding process, during which major transcriptomic changes and metabolic rearrangements occur within the fruit. In apple, the drop of fruits at different positions within the cluster can be selectively magnified through chemical thinners, such as benzyladenine and metamitron, acting as abscission enhancers. In the present research, different abscission potentials were obtained within the apple fruitlet population by means of the above cited thinners. A metabolomic study was conducted on the volatile organic compounds (VOCs) emitted by abscising fruitlets, allowing to identify isoprene as an early marker of abscission induction. A strong correlation was also observed between isoprene production and abscisic acid (ABA) levels in the fruit cortex, which were shown to increase in abscising fruitlets with respect to non-abscising ones. Transcriptomic evidence indicated that abscission-related ABA is biologically active and its increased biosynthesis is associated with the induction of a specific ABA-responsive NCED (9-cis-epoxycarotenoid dioxygenase) gene. According to a hypothetical model, ABA may transiently cooperate with other hormones and secondary messengers in the generation of an intra-fruit signal leading to the downstream activation of the abscission zone. The shedding process therefore appears to be triggered by multiple interdependent pathways, whose fine regulation, exerted within a very short temporal window by both endogenous and exogenous factors, determines the final destiny of the fruitlets

Influence of olive (cv Grignano) fruit ripening and oil extraction under different nitrogen regimes on volatile organic compound emissions studied by PTR-MS technique

Volatile organic compounds of extra virgin olive oils obtained from the local Italian cultivar Grignano were measured by proton transfer reaction–mass spectrometry (PTR-MS). Oils were extracted by olives harvested at different ripening stages across veraison, performing each extraction step and the whole extraction process in nitrogen atmosphere to observe the changes in the volatile profiles of the oils. Principal component analysis carried out on the full spectral signature of the PTR-MS measurements showed that the stage of ripening has a stronger effect on the global definition of volatile profiles than the use of nitrogen during oil extraction. The fingerprint-like chemical information provided by the spectra were used to construct a heat map, which allowed the dynamical representation of the multivariate nature of mass evolution during the ripening process. This provided the first evidence that some groups of volatile organic compounds displayed a time course of regulation with coordinated increasing or decreasing trends in association with specific stages of fruit ripening