Chemical Diversity and Defence Metabolism: How Plants Cope with Pathogens and Ozone Pollution

Chemical defences represent a main trait of the plant innate immune system. Besides regulating the relationship between plants and their ecosystems, phytochemicals are involved both in resistance against pathogens and in tolerance towards abiotic stresses, such as atmospheric pollution. Plant defence metabolites arise from the main secondary metabolic routes, the phenylpropanoid, the isoprenoid and the alkaloid pathways. In plants, antibiotic compounds can be both preformed (phytoanticipins) and inducible (phytoalexins), the former including saponins, cyanogenic glycosides and glucosinolates. Chronic exposure to tropospheric ozone (O3) stimulates the carbon fluxes from the primary to the secondary metabolic pathways to a great extent, inducing a shift of the available resources in favour of the synthesis of secondary products. In some cases, the plant defence responses against pathogens and environmental pollutants may overlap, leading to the unspecific synthesis of similar molecules, such as phenylpropanoids. Exposure to ozone can also modify the pattern of biogenic volatile organic compounds (BVOC), emitted from plant in response to herbivore feeding, thus altering the tritrophic interaction among plant, phytophagy and their natural enemies. Finally, the synthesis of ethylene and polyamines can be regulated by ozone at level of S-adenosylmethionine (SAM), the biosynthetic precursor of both classes of hormones, which can, therefore, mutually inhibit their own biosynthesis with consequence on plant phenotype

Anthocyanins in cereals

[EN] The anthocyanic composition of some pigmented cereals is still not well established, neither in relation to some of their components, nor from the quantitative point of view. Nonetheless, the use of analytical techniques, such as diode array spectroscopy and mass spectrometry (MS, PDMS, MALDI) coupled or not to liquid chromatography, are permitting, in recent years, the confirmation of the structure of some of the principal anthocyanins and a knowledge of those which are present in minor proportion. In this article, firstly, a review of the principal methods of analysis of anthocyanins is made. This is followed by a review of the most significant advances achieved in the last years in the field of the identification and quantification of these pigments in cereals and the present uses of the commercial extracts of anthocyanins obtained from these sources and the perspectives for their use is included

Induction of pathogen defence genes in parsley (<em>Petroselinum crispim</em> L.) plant by ozone.

Parsley (Petroselinum crispum L.) is known to respond to pathogen attack by the synthesis of furanocoumarins and to UV-irradiation by the synthesis of flavone glycosides, whereas ozone treatment results in the induction of both pathways. Ozone treatment (200 nl 1&minus;1, 10 h) of parsley seedlings results in an increased mRNA level of early genes within 3 h [pathogenesis related proteins PR1, PR2 and an elicitor-induced protein with unknown function (Eli 16)], of intermediate induced genes within 6 h [phenylalanine ammonia-lyase (PAL), 4-coumaroyl-CoA ligase (4CL), chalcone synthase (CHS)], and of late genes within 12 h [hydroxyproline-rich glycoprotein (HRGP), peroxidase (POD)]. 2D-PAGE of in vitro translated poly(A)+ RNA isolated from ozone-treated parsley seedlings revealed about 20 induced and 10 repressed translation products. A cDNA library from parsley seedlings was differential screened, yielding several induced cDNA clones. One of the ozone-induced cDNA clones could be identified as coding for PR1-1 by hybrid-selected in vitro translation and by DNA sequence analysis

Cross-induction of defensive phenylpropanoid pathways in parsley (<em>Petroselinum crispum</em> L.) plants by ozone.

Parsley cell cultures are known to respond to fungal elicitor with an accumulation of furanocoumarin phytoalexins, whereas UV-irradiation induces the synthesis of flavonoid glycosides. In this report we summarize the influence of ozone on the two stress pathways in parsley plants at the levels of secondary metabolism, enzyme activities as well as transcript amounts. Ozone treatment resulted in the simultaneous induction of both pathways of phenylpropanoid metabolism (&quot;cross induction&quot;)

Biochemical Plant Responses to Ozone (IV. Cross-Induction of Defensive Pathways in Parsley (Petroselinum crispum L.) Plants).

Parsley (Petroselinum crispum L.) is known to respond to ultraviolet irradiation by the synthesis of flavone glycosides, whereas fungal or elicitor stress leads to the synthesis of furanocoumarin phytoalexins. We tested how these defensive pathways are affected by a single ozone treatment (200 nL L-1; 10 h). Assays were performed at the levels of transcripts, for enzyme activities, and for secondary products. The most rapid transcript accumulation was maximal at 3 h, whereas flavone glycosides and furanocoumarins were maximally induced at 12 and 24 h, respectively, after the start of ozone treatment. Ozone acted as a cross-inducer because the two distinct pathways were simultaneously induced. These results are consistent with the previously observed ozone induction of fungal and viral defense reactions in tobacco, spruce, and pine

Differential transcript induction of parsley pathogenesis-related proteins and of a small heat shock protein by ozone and heat shock.

Parsley (Petroselinum (crispum L.) is known to respond to pathogen attack by the synthesis of furanocoumarins and to UV irradiation by the synthesis of flavone glycosides whereas ozone treatment results in the induction of both pathways. A cDNA library from parsley plants was differentially screened using labelled reverse-transcribed poly(A)+ RNA isolated from ozone-treated parsley plants. This resulted in the isolation of 13 independent cDNA clones representing ozone-induced genes and of 11 cDNA clones representing ozone-repressed genes. DNA sequencing of several clones resulted in the identification of pathogenesis-related protein 1-3 (PR1-3), of a new member of PR1 cDNAs (PRI-4) and of a small heat shock protein (sHSP). Northern blot analyses showed a transient induction of the three mRNA species after ozone fumigation. In contrast, heat shock treatment of parsley plants resulted in an increase of sHSP mRNA whereas no increase for transcripts of PR1-3 and PR1-4 could be observed. This is the first characterized sHSP cDNA clone for plants induced by heat shock, as well as by oxidative stress caused by ozone

Oxidative Stress and Plant Secondary Metabolism: 6&quot;-O-malonylapiin in Parsley.

A screening method using LC-DAD-ESI/MS was applied to the analysis of flavonoids in celery, Chinese celery, and celery seeds (Apium graveolens L. and varieties). Fifteen flavonoid glycosides were detected in the three celery materials. They were identified as luteolin 7-O-apiosylglucoside, luteolin 7-O-glucoside, apigenin 7-O-apiosylglucoside, chrysoeriol 7-O-apiosylglucoside, chrysoeriol 7-O-glucoside, and more than 10 malonyl derivatives of these glycosides. The identification of the malonyl derivatives was confirmed by their conversion into glycosides upon heating and by comparison of some of the malonates with malonates that had previously been identified in red bell pepper and parsley. The concentrations of the glycosides and the malonyl glycosides in the three materials were estimated by comparison to aglycone standards. This is the first report of the presence of these glycosylated flavonoid malonates in celery

Photosynthetic process and activities of enzymes involved in the phenylpropanoid pathway in resistant and sensitive genotypes of Lycopersicon esculentum L. exposed to ozone

Two differential pathogen-sensitive genotypes of Lycopersicon esculentum plants were treated with a single pulse of ozone (150 nL L1 for 3 h) and the photosynthetic process and activity of some enzymes of phenylpropanoid metabolism were studied. The sensitive to pathogen variety, Cuor di Bue, showed visible symptoms of injury following the ozone fumigation while the pathogen resistant line 93.1033/1 did not. CO2 fixation ability was compromised in both genotypes but in line 93.1033/1 a complete recovery in photoassimilation of CO2 was observed the day after the end of the fumigation when in Cuor di Bue a further decrease was recorded. No differences between the two tomato lines were found in chlorophyll fluorescence parameters. Shikimate dehydrogenase (SKDH; E.C. 1.1.1.25), L-phenylalanine ammonia-lyase (PAL; E.C. 4.3.1.5) and cinnamyl alcohol dehydrogenase (CAD; E.C. 1.1.1.195) activities in particular were assayed 24 h after the end of the O3 treatment in order to obtain additional information on the biochemical parameters involved in the ozone response. PAL and SKDH increased significantly only in line 93.1033/1 while CAD diminished in both the genotypes. In the resistant line a mechanism attributable to that induced by fungal pathogens was presumable. On the contrary, no clear behavior could be followed for Cuor di Bue