Overexpression of the lemon basil α-zingiberene synthase gene increases both mono- and sesquiterpene contents in tomato fruit

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75154/1/j.1365-313X.2008.03599.x.pd

Study of 'Redhaven' peach and its white-fleshed mutant suggests a key role of CCD4 carotenoid dioxygenase in carotenoid and norisoprenoid volatile metabolism

<p>Abstract</p> <p>Background</p> <p>Carotenoids are plant metabolites which are not only essential in photosynthesis but also important quality factors in determining the pigmentation and aroma of flowers and fruits. To investigate the regulation of carotenoid metabolism, as related to norisoprenoids and other volatile compounds in peach (<it>Prunus persica </it>L. Batsch.), and the role of carotenoid dioxygenases in determining differences in flesh color phenotype and volatile composition, the expression patterns of relevant carotenoid genes and metabolites were studied during fruit development along with volatile compound content. Two contrasted cultivars, the yellow-fleshed 'Redhaven' (RH) and its white-fleshed mutant 'Redhaven Bianca' (RHB) were examined.</p> <p>Results</p> <p>The two genotypes displayed marked differences in the accumulation of carotenoid pigments in mesocarp tissues. Lower carotenoid levels and higher levels of norisoprenoid volatiles were observed in RHB, which might be explained by differential activity of carotenoid cleavage dioxygenase (CCD) enzymes. In fact, the <it>ccd4 </it>transcript levels were dramatically higher at late ripening stages in RHB with respect to RH. The two genotypes also showed differences in the expression patterns of several carotenoid and isoprenoid transcripts, compatible with a feed-back regulation of these transcripts. Abamine SG - an inhibitor of CCD enzymes - decreased the levels of both isoprenoid and non-isoprenoid volatiles in RHB fruits, indicating a complex regulation of volatile production.</p> <p>Conclusions</p> <p>Differential expression of <it>ccd4 </it>is likely to be the major determinant in the accumulation of carotenoids and carotenoid-derived volatiles in peach fruit flesh. More in general, dioxygenases appear to be key factors controlling volatile composition in peach fruit, since abamine SG-treated 'Redhaven Bianca' fruits had strongly reduced levels of norisoprenoids and other volatile classes. Comparative functional studies of peach carotenoid cleavage enzymes are required to fully elucidate their role in peach fruit pigmentation and aroma.</p

Metabolic networking in Brunfelsia calycina petals after flower opening

Brunfelsia calycina flowers change colour from purple to white due to anthocyanin degradation, parallel to an increase in fragrance and petal size. Here it was tested whether the production of the fragrant benzenoids is dependent on induction of the shikimate pathway, or if they are formed from the anthocyanin degradation products. An extensive characterization of the events taking place in Brunfelsia flowers is presented. Anthocyanin characterization was performed using ultraperfomance liquid chromatography–quadrupole time of flight–tandem mass specrometry (UPLC-QTOF-MS/MS). Volatiles emitted were identified by headspace solid phase microextraction–gas chromatography–mass spectrometry (HS-SPME-GC-MS). Accumulated proteins were identified by 2D gel electrophoresis. Transcription profiles were characterized by cross-species hybridization of Brunfelsia cDNAs to potato cDNA microarrays. Identification of accumulated metabolites was performed by UPLC-QTOF-MS non-targeted metabolite analysis. The results include characterization of the nine main anthocyanins in Brunfelsia flowers. In addition, 146 up-regulated genes, 19 volatiles, seven proteins, and 17 metabolites that increased during anthocyanin degradation were identified. A multilevel analysis suggests induction of the shikimate pathway. This pathway is the most probable source of the phenolic acids, which in turn are precursors of both the benzenoid and lignin production pathways. The knowledge obtained is valuable for future studies on degradation of anthocyanins, formation of volatiles, and the network of secondary metabolism in Brunfelsia and related species

Expressed sequence tag analysis of khat (Catha edulis) provides a putative molecular biochemical basis for the biosynthesis of phenylpropylamino alkaloids

Khat (Catha edulis Forsk.) is a flowering perennial shrub cultivated for its neurostimulant properties resulting mainly from the occurrence of (S)-cathinone in young leaves. The biosynthesis of (S)-cathinone and the related phenylpropylamino alkaloids (1S,2S)-cathine and (1R,2S)-norephedrine is not well characterized in plants. We prepared a cDNA library from young khat leaves and sequenced 4,896 random clones, generating an expressed sequence tag (EST) library of 3,293 unigenes. Putative functions were assigned to > 98% of the ESTs, providing a key resource for gene discovery. Candidates potentially involved at various stages of phenylpropylamino alkaloid biosynthesis from L-phenylalanine to (1S,2S)-cathine were identified

Branched-chain and aromatic amino acid catabolism into aroma volatiles in Cucumis melo L. fruit

The unique aroma of melons (Cucumis melo L., Cucurbitaceae) is composed of many volatile compounds biosynthetically derived from fatty acids, carotenoids, amino acids, and terpenes. Although amino acids are known precursors of aroma compounds in the plant kingdom, the initial steps in the catabolism of amino acids into aroma volatiles have received little attention. Incubation of melon fruit cubes with amino acids and α-keto acids led to the enhanced formation of aroma compounds bearing the side chain of the exogenous amino or keto acid supplied. Moreover, L-[13C6]phenylalanine was also incorporated into aromatic volatile compounds. Amino acid transaminase activities extracted from the flesh of mature melon fruits converted L-isoleucine, L-leucine, L-valine, L-methionine, or L-phenylalanine into their respective α-keto acids, utilizing α-ketoglutarate as the amine acceptor. Two novel genes were isolated and characterized (CmArAT1 and CmBCAT1) encoding 45.6 kDa and 42.7 kDa proteins, respectively, that displayed aromatic and branched-chain amino acid transaminase activities, respectively, when expressed in Escherichia coli. The expression of CmBCAT1 and CmArAT1 was low in vegetative tissues, but increased in flesh and rind tissues during fruit ripening. In addition, ripe fruits of climacteric aromatic cultivars generally showed high expression of CmBCAT1 and CmArAT1 in contrast to non-climacteric non-aromatic fruits. The results presented here indicate that in melon fruit tissues, the catabolism of amino acids into aroma volatiles can initiate through a transamination mechanism, rather than decarboxylation or direct aldehyde synthesis, as has been demonstrated in other plants

Flower proteome: changes in protein spectrum during the advanced stages of rose petal development

Flowering is a unique and highly programmed process, but hardly anything is known about the developmentally regulated proteome changes in petals. Here, we employed proteomic technologies to study petal development in rose ( Rosa hybrida ). Using two-dimensional polyacrylamide gel electrophoresis, we generated stage-specific (closed bud, mature flower and flower at anthesis) petal protein maps with ca. 1,000 unique protein spots. Expression analyses of all resolved protein spots revealed that almost 30% of them were stage-specific, with ca. 90 protein spots for each stage. Most of the proteins exhibited differential expression during petal development, whereas only ca. 6% were constitutively expressed. Eighty-two of the resolved proteins were identified by mass spectrometry and annotated. Classification of the annotated proteins into functional groups revealed energy, cell rescue, unknown function (including novel sequences) and metabolism to be the largest classes, together comprising ca. 90% of all identified proteins. Interestingly, a large number of stress-related proteins were identified in developing petals. Analyses of the expression patterns of annotated proteins and their corresponding RNAs confirmed the importance of proteome characterization.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47485/1/425_2005_Article_1512.pd