A purified glycoprotein from Botrytis cinerea (strain T4), identified as endopolygalacturonase 1 (T4BcPG1) by mass spectrometry analysis, has been shown to activate defense reactions in grapevine (Vitis vinifera cv. Gamay). These reactions include calcium influx, production of active oxygen species, activation of two mitogen-activated protein kinases, defense gene transcript accumulation, and phytoalexin production. Most of these defense reactions were also activated in grapevine in response to purified oligogalacturonides (OGA) with a degree of polymerization of 9 to 20. In vivo, these active OGA might be a part of the released products resulting from endopolygalacturonase activity on plant cell walls. Nevertheless, the intensity and kinetics of events triggered by OGA were very different when compared with T4BcPG1 effects. Moreover, chemical treatments of T4BcPG1 and desensitization assays have allowed us to discriminate enzymatic and elicitor activities, indicating that elicitor activity was not due to released oligogalacturonides. Thus, BcPG1 should be considered as both an avirulence and a virulence factor. The role of the secreted BcPG1 in the pathogenicity of Botrytis cinerea is discussed.

We have already reported the identification of the endopolygalacturonase 1 (BcPG1) from Botrytis cinerea as a potent elicitor of defense responses in grapevine, independently of its enzymatic activity. The aim of the present study is the analysis of the signaling pathways triggered by BcPG1 in grapevine cells. Our data indicate that BcPG1 induces a Ca2+ entry from the apoplasm, which triggers a phosphorylation-dependent nitric oxide (NO) production via an enzyme probably related to a NO synthase. Then NO is involved in (i) cytosolic calcium homeostasis, by activating Ca2+ release from internal stores and regulating Ca2+ fluxes across the plasma membrane, (ii) plasma membrane potential variation, (iii) the activation of active oxygen species (AOS) production, and (iv) defense gene expression, including phenylalanine ammonia lyase and stilbene synthase, which encode enzymes responsible for phytoalexin biosynthesis. Interestingly enough, mitogen-activated protein kinase (MAPK) activation is independent of this regulation pathway that closely connects Ca2+, NO, and AOS.

Four ATP-binding cassette (ABC) half-transporters have been identified in mammalian peroxisomes: adrenoleukodystrophy protein (ALDP), adrenoleukodystrophy-related protein (ALDRP), 70-kDa peroxisomal membrane protein (PMP70) and PMP70-related protein (P70R). Inherited defects in ALDP cause the neurodegenerative disorder X-linked adrenoleukodystrophy (X-ALD). By comparative Northern blot analyses we found each of the four murine peroxisomal ABC transporter mRNA species at maximum abundance only in a few tissues, which differed for each family member. The four genes were also regulated differentially during mouse brain development: ALDP mRNA was most abundant in embryonic brain and gradually decreased during maturation; ALDRP and P70R mRNA accumulated in the early postnatal period; and the amount of PMP70 transcript increased slightly during the second and third postnatal week. The different expression patterns could explain why b-oxidation is defective in X-ALD, although ALDRP and PMP70 can replace ALDP functionally in fibroblasts. Dietary fenofibrate had no effect on the ALD and P70R genes, but strongly increased expression of the ALDR and PMP70 genes in mouse liver. However, in P-glycoprotein Mdr1a-deficient mice fenofibrate treatment increased ALDR gene expression also in the brain, suggesting that the multidrug-transporter P-glycoprotein restricts entry of fenofibrate to the brain at the blood±brain barrier. Analysis of the promoter sequences revealed a cryptic nuclear hormone receptor response element of the DR+4 type in the ALDR promoter and a novel 18-bp sequence motif present only in the 5 H flanking DNA of the ALDR and PMP70 genes. The mouse ALDR gene uses a single transcription start site but alternative polyadenylation sites. These data are of importance for the use of ALDP-deficient mice as a model in pharmacological gene therapy studies.Keywords: adrenoleukodystrophy; ATP-binding cassette transporter; fenofibrate; gene expression; peroxisome.Four ABC-transporters have been identified in the mammalian peroxisomal membrane: adrenoleukodystrophy protein (ALDP), adrenoleukodystrophy-related protein (ALDRP), 70 kDa peroxisomal membrane protein (PMP70) and PMP70-related protein (P70R/PMP69). Relative to ALDP the human proteins display 63%, 36%, and 25% amino acid identity [1], respectively, and all have the predicted structure of a half-transporter with one membrane spanning domain and one nucleotide binding fold. As most of the half-transporters identified to date function as dimers, it has been suggested that the peroxisomal ABCtransporters also need to assemble as homo-or heterodimers in order to form a functional unit [2,3].Although the exact functions and substrates of the mammalian peroxisomal ABC-transporters have yet to be defined, the detrimental effects of a deficient transporter is demonstrated by mutations in the ALD gene, leading to the lipid storage disorder X-linked adrenoleukodystrophy (X-ALD, McKusick #300100). Biochemically X-ALD is characterized by defective peroxisomal b-oxidation of sat...

The aim of the present study was to investigate whether unsaturated 2‐acyl‐lysophosphatidylcholine bound to plasma albumin is a relevant delivery form of unsaturated fatty acids to the developing brain. Twenty‐day‐old rats were perfused for 30 s with labeled palmitic, oleic, linoleic, and arachidonic acids in either their unesterified form or esterified in 2‐acyl‐lysophosphatidylcholine labeled on the choline and fatty acid moieties. Both forms were bound to albumin. Incorporation in brain lipid classes was followed within 1 h. The brain uptake of the unesterified fatty acids reached a plateau at 5–155 mim and was maximal for arachidonic acid (0.45% of the perfused dose). The brain uptake of palmitoyl‐lysophosphatidylcholine was similar to that of palmitic acid, whereas that of other lysophosphatidylcholines increased with the degree of unsaturation (rate and maximal uptake) and was six‐ to 10‐fold higher than that of the corresponding unesterified fatty acid. 2‐Acyl‐lysophosphatidylcholines were taken up without prior hydrolysis and reacylated into doubly labeled phosphatidylcholine, which was the most labeled lipid class, whereas lipid distribution of the unesterified fatty acid was more diversi fied. Partial hydrolysis of 2‐acyl‐lysophosphatidylcholine occurred in the brain tissue, and redistribution of the fatty acyl moiety into other phospholipid classes was also observed and was the highest for arachidonic acid. In this case, the percentage of esterification of this fatty acid in phosphatidylinositol (expressed as a percentage of the total lipid fraction) was relatively lower than that observed when the unesterified form was used. 1‐Acyl‐lysophosphatidylcholine (palmitoyl) was taken at the same extent that 2‐acyllysophosphatidylcholine but was more hydrolyzed and reesterified in other lipid classes than 2‐acyl isomer. All these results suggest that 2‐acyl‐lysophosphatidylcholine bound to albumin could be an efficient delivery form of unsaturated fatty acids to the developing rat brain and that the fatty acid delivery form could modulate their fate in the tissue.

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