Ricerche sul funzionamento e sulle diverse modalita' di attivazione e di regolazione del ciclo delle xantofille

Dottorato di ricerca in botanica applicata. 9. ciclo. A.a. 1995-96. Coordinatore B. Romano. Docente guida M. AntonielliConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Effects of short-term ozone fumigation on tobacco plants: response of the scavenging system and expression of the glutathione reductase

The role that the constituents of the ascorbate-glutathione cycle play in the mechanism of contrasting ozone sensitivities was examined in mature and old tobacco leaves after acute ozone-fumigation (150 p.p.b., 5 h). Levels of the enzyme activities associated with the detoxifying system were lower in ozone-sensitive Bel W3 control plants than in unfumigated ozone-tolerant Bel B plants. In particular, the endogenous activities of ascorbate peroxidase (APX) and glutathione reductase (GR), and the metabolites ascorbic acid (AA) and reduced glutathione (GSH) were more abundant in Bel B than Bel W3 control plants. These results suggest that the higher tolerance of Bel B to O3 is associated with a greater initial content of the antioxidant enzymes or metabolites. Only in the mature leaves of the ozone-tolerant Bel B cv. did fumigation trigger activation of APX and, weakly, of dehydroascorbate reductase (DHAR). The activity of these enzymes was significantly lower after ozone treatment in both mature and old leaves of Bel W3 than in control plants. Fumigation had little effect on the ascorbate content. Its main effects on the glutathione pool were that it boosted the oxidized form and lowered the reduced form, particularly in mature Bel W3 leaves. Extractable GR activity remained unchanged in both Bel B and Bel W3 immediately after fumigation, but increased slightly 24 h later, particularly in mature leaves of Bel W3. Exposure to O3 caused a sharp decline in chloroplastic GR mRNA levels in both cultivars. However, as Western blot analysis failed to detect any major changes in GR protein content at this time, the protein must be highly stable. There is therefore a good correlation between tolerance to O3 and high endogenous levels of antioxidant metabolites such as AA and GSH in tobacco. In addition, the degree of inducibility of the system discriminates the two cultivars investigated

Jasmonate-mediated defence responses, unlike salicylate-mediated responses, are involved in the recovery of grapevine from bois noir disease

Abstract Background Bois noir is an important disease of grapevine (Vitis vinifera L.), caused by phytoplasmas. An interesting, yet elusive aspect of the bois noir disease is “recovery”, i.e., the spontaneous and unpredictable remission of symptoms and damage. Because conventional pest management is ineffective against bois noir, deciphering the molecular bases of recovery is beneficial. The present study aimed to understand whether salicylate- and jasmonate-defence pathways might have a role in the recovery from the bois noir disease of grapevine. Results Leaves from healthy, bois noir-diseased and bois noir-recovered plants were compared, both in the presence (late summer) and absence (late spring) of bois noir symptoms on the diseased plants. Analyses of salicylate and jasmonate contents, as well as the expression of genes involved in their biosynthesis, signalling and action, were evaluated. In symptomatic diseased plants (late summer), unlike symptomless plants (late spring), salicylate biosynthesis was increased and salicylate-responsive genes were activated. In contrast, jasmonate biosynthesis and signalling genes were up-regulated both in recovered and diseased plants at all sampling dates. The activation of salicylate signalling in symptomatic plants might have antagonised the jasmonate-mediated defence response by suppressing the expression of jasmonate-responsive genes. Conclusions Our results suggest that grapevine reacts to phytoplasma infection through salicylate-mediated signalling, although the resultant full activation of a salicylate-mediated response is apparently ineffective in conferring resistance against bois noir disease. Activation of the salicylate signalling pathway that is associated with the presence of bois noir phytoplasma seems to antagonise the jasmonate defence response, by failing to activate or suppressing both the expression of some jasmonate responsive genes that act downstream of the jasmonate biosynthetic pathway, as well as the first events of the jasmonate signalling pathway. On the other hand, activation of the entire jasmonate signalling pathway in recovered plants suggests the potential importance of jasmonate-regulated defences in preventing bois noir phytoplasma infections and the subsequent development of bois noir disease. Thus, on one hand, recovery could be achieved and maintained over time by preventing the activation of defence genes associated with salicylate signalling, and on the other hand, by activating jasmonate signalling and other defence responses

Similar foliar lesions but opposite hormonal patterns in a tomato mutant impaired in ethylene perception and its near isogenic wild type challenged with ozone

The accumulation of ethylene (Er), hydrogen peroxide (H(2)O(2)), nitric oxide (NO), salicylic (SA) and jasmonic (JA) acids, as well as the transcriptional activation of JA-biosynthetic and hypersensitive response (HR) marker genes were examined in ET-insensitive Never ripe (Nr) mutant of tomato (Lycopersicon esculentum L) and in its near isogenic wild type (WT, cv. New Yorker) during and after an acute ozone (03) fumigation. The scoring of O(3)-induced foliar symptoms indicated similar sensitivity between WT and Nr. In both genotypes the O(3)-induced ET emission peaked after 3 h of fumigation, although with different intensities between them; H(2)O(2) and NO bursts occurred, both showing a biphasic time course. However, SA and JA revealed opposite accumulation patterns: in Nr a high level of SA but a low JA accumulation were observed, whereas in WT a marked evolution of JA but a weak SA accumulation were detected. The transcription of certain JA-biosynthetic and HR-inducible genes was similarly activated by O(3) in the two tomato lines. According to the current models on the molecular events leading to the development of O(3)-induced foliar symptoms, here we suggest that the partial ET-insensitivity of Nr would have promoted a SA build-up, leading to cell death and to a reduced JA accumulation. In WT the O(3)-induced leaf injury without SA build-up but with JA accumulation would have arisen from the perception of high ET and H(2)O(2) level

Additional file 1: Table S1. of Jasmonate-mediated defence responses, unlike salicylate-mediated responses, are involved in the recovery of grapevine from bois noir disease

Vitis vinifera gene sequences coding for phenylalanine ammonia-lyase (PAL) and isochorismate synthase (ICS), identified in the National Center for Biotechnology Information (NCBI) database and used in the synthesis of oligonucleotides for expression analysis. Table S2. Vitis vinifera gene sequences coding for lipoxygenase (LOX), allene oxide synthase (AOS), allene oxide cyclase (AOC), 12-oxo-phytodienoic acid (OPDA) reductase (OPR), and jasmonate carboxyl methyltransferase (JMT), identified in the NCBI database and used in the synthesis of oligonucleotides for expression analysis. Table S3. Vitis vinifera gene sequences involved in salicylate (NPR1.1, NPR1.2 and EDS1) or jasmonate (MYC2, JAZ1, JAZ2 and JAZ3) signalling pathways, identified in the NCBI database and used in the synthesis of oligonucleotides for expression analysis. Table S4. Vitis vinifera gene sequences coding for WRKY transcription factors, identified in the NCBI database and used in the synthesis of oligonucleotides for expression analysis. Table S5. Vitis vinifera gene sequences coding for pathogenesis-related proteins (PRP), identified in the NCBI database and used in the synthesis of oligonucleotides for expression analysis. Table S6. Vitis vinifera gene sequences coding for stilbene synthase (STS) and MYB transcription factors that specifically interact with the STS promoter, identified in the NCBI database and used in the synthesis of oligonucleotides for expression analysis. Table S7. Vitis vinifera gene sequences coding for chalcone synthase (CHS), identified in the NCBI database and used in the synthesis of oligonucleotides for expression analysis. Table S8. Vitis vinifera sequences coding for candidate reference genes, identified in the NCBI database and used in the synthesis of oligonucleotides for the normalisation of expression data in qRT-PCR analyses. (DOC 358 kb

Ozone affects pollen viability and NAD(P)H oxidase release from Ambrosia artemisiifolia pollen

Air pollution is frequently proposed as a cause of the increased incidence of allergy in industrialised countries. We investigated the impact of ozone (O3) on reactive oxygen species (ROS) and allergen content of ragweed pollen (Ambrosia artemisiifolia). Pollen was exposed to acute O3 fumigation, with analysis of pollen viability, ROS and nitric oxide (NO) content, activity of nicotinamide adenine dinucleotide phosphate (NAD[P]H) oxidase, and expression of major allergens. There was decreased pollen viability after O3 fumigation, which indicates damage to the pollen membrane system, although the ROS and NO contents were not changed or were only slightly induced, respectively. Ozone exposure induced a significant enhancement of the ROS-generating enzyme NAD(P)H oxidase. The expression of the allergen Amb a 1 was not affected by O3, determined from the mRNA levels of the major allergens. We conclude that O3 can increase ragweed pollen allergenicity through stimulation of ROS-generating NAD(P)H oxidase