Helen A. Norman

Induction of phenylpropanoid pathway enzymes in elicitor-treated cultures ofCephalocereus senilis

Abstract Treatment of old-man-cactus ( Cephalocereus senilis ) suspension cultures with chitin elicits synthesis of an aurone phytoalexin, cephalocerone. Elicitor-induced de novo synthesis of cephalocerone was demonstrated by incubating elicited cactus cultures with [ 3 H]phenylalanine; this resulted in the labelling of five induced phenolic compounds including cephalocerone. Increased extractable activities of the phenylpropanoid pathway enzymes phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS) and chalcone isomerase (CHI) accompanied the synthesis of cephalocerone. CHS and PAL, which are both involved in the biosynthesis of cephalocerone, showed maximum activity at 12 and 24 hr post-elicitation, respectively. CHS and CHI activities catalysing the synthesis and subsequent isomerization of 2′,4′,6′-trihydroxychalcone were present in the cell cultures, consistent with the formation of cephalocerone via a chalcone with no B-ring substituents.

Flavonoids as markers for Erythroxylum Taxa: E. coca var. ipadu and E. novogranatense var. truxillense

Abstract Leaf extracts of Erythroxylum coca var. ipadu Plowman (E. c. var. ipadu) produced five O-conjugates of taxifolin and one O-conjugate of quercetin flavonoids, while the equivalent extract from Erythroxylum novogranatense var. truxillense (Rusby) Plowman (E. n. var. truxillense) afforded four flavonoids: (a) the first, an O-conjugate of quercetin; (b) the second, an O-conjugate of fisetin; and (c) the third and fourth O-conjugates of kaempferol. The flavonols of E. n. var. truxillense contained 4′-OEt whereas in E. c. var. ipadu none was found. E. n. var. truxillense contained the flavonol fisetin which was not found in E. c. var. ipadu and has not been previously reported for the taxa. The major sugars in leaf extracts were acylated rhamnosides with either 7, 3 or 4′ linkage or combinations thereof. Flavonoids of the four cultivated Erythroxylum taxa, all of which contain the cocaine alkaloid, differ, and may be used as chemotaxonomic markers for the taxa.

Effects of acclimation to low temperature and to water stress on photosynthesis and on physical and chemical properties of lipids from thylakoids of cucumber and cotton

Abstract The effects of growth at low temperature and under water stress on the physical and chemical properties of lipids of thylakoids from leaves of cucumber ( Cucumis sativis L. cv. Beit Alpha MR) and cotton ( Gossypium hirsutum L. cv. glandless Stoneville 213) were examined. The phospholipid transition temperature (measured by fluorescence polarization) was not different in cold-grown, water-stressed, or warm-grown control plants. These treatments also had no effect on the critical temperatures for chilling injury to photosynthetic oxygen evolution or for heat-induced increase in chlorophyll fluorescence. The molecular species compositions of cucumber and cotton thylakoid phosphatidylglycerols were compared to those of other chilling-sensitive plants and to those of plants able to acclimate. The acclimation treatments caused no changes in the phosphatidylglycerol molecular species of cucumber. However, in cold-grown cotton there was a marked decrease in the content of molecular species with high melting points. Collectively the results suggest that changes in phosphatidylglycerol molecular species composition are not always indicative of a critical process required for chilling resistance.

Identification of covalently bound fatty acids on acylated proteins immoblized on nitrocellulose paper

A general method for identification of fatty acids covalently bound to acylated proteins following their electrophoretic transfer onto nitrocellulose paper is described. As demonstrated for [3H]palmitoylated RAS1 protein of Saccharomyces cerevisiae and the acylated acyl carrier protein of Spirodela oligorrhiza, this procedure alleviates the need for elution of proteins from polyacrylamide gel slices. Fatty acid ligands of such proteins are hydrolyzed directly from their immobilized state on the nitrocellulose paper, then derivatized with p-nitrophenacyl bromide, and finally resolved by reversed-phase high-performance liquid chromatography. The amount of acylated protein required for identification of acyl groups is minimized compared to that required for more conventional approaches by coupling a radioactive flow detector with the HPLC system.

LEAF FLAVONOIDS AS CHEMOTAXONOMIC MARKERS FOR TWO ERYTHROXYLUM TAXA

Leaf extracts of Erythroxylum coca var. coca Lam. (E. c. var. coca) yielded six O-eonjugates of Eriodictyol flavonoids, while the equivalent extracts from Erythroxylum novogranatense var. novogranatense (Morris) Hieron (E. n. var. novogranatense) contained five flavonoids, two of which were O-conjugates of Luteolin and three were O-conjugates of Kaempferol. All six of E. c. var. coca methanolic extracted peaks (resolved by HPLC) were found to have a 2, 3 single bond, which in E. n. var. novogranatense is replaced by a 2- hydroxy allene. The other primary difference in the predominant flavonoids between these taxa is the chemical composition of the sugar and/or acyl O-conjugation and site(s) at which this conjugation occurred. The results suggest that the most abundant O-conjugated flavonoids of E. c. var. coca and E. n. var. novogranatense may be used as chemotaxonomic markers for the two taxa. Therefore, the O-conjugated peaks of Eriodictyol , are distinct chemotaxonomic markers for E. c. var. coca and the O-conjugated peaks Luteolin and Kaempferol for E. n. var. novogranatense. These taxa are two of the four cultivated Erythroxylum taxa that contain commercial quantities of the cocaine alkaloid in their leaves, this entity also sets apart the taxa from other members of Erythroxylum. We suggest that the biochemistry of flavonoids of other Erythroxylum taxa may also be species selective

Response of beans and hairy fleabane leaves to ozone and paraquat with and without the antiozonant, ethylenediurea

Abstract Growth chamber experiments were conducted to determine if there is a pattern of cross-tolerance to paraquat and ozone (O 3 ) using an O 3 -insensitive bean ( Phaseolus vulgaris L.) genotype, and paraquat-resistant hairy fleabane [ Conyza bonariensis (L.) Cronq.] biotype. The additional objective was to determine if the antiozonant, EDU, protects seedlings against paraquat injury. Bean and fleabane seedlings were treated with EDU and exposed to O 3 at 0, 0.1, 0.3 and 0.5 ppm (v/v) for 6 hr or paraquat at 0, 0.1, 0.3 and 0.5 mM. Responses were evaluated by measuring fresh weight and chlorophyll content. EDU protected the O 3 -sensitive bean genotype and both hairy fleabane biotypes from O 3 injury. However, EDU did not improve the tolerance of the paraquat-susceptible hairy fleabane or the two bean genotypes to paraquat. The paraquat-resistant hairy fleabane was not tolerant to O 3 , and the O 3 -insensitive bean genotype did not show resistance to paraquat. No cross-tolerance between O 3 and paraquat in beans and hairy fleabane was detected.

Lipid Molecular Species Composition of Granal and Stromal Lamellae

We are investigating the lipid biosynthetic pathways involved in both the development of chloroplast membranes and the lipid-protein interactions in a mature chloroplast. We report the molecular species compositions of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) from highly purified granal and stromal lamellae of Splrodela oligorrhiza. Characteristic differences in the lipids suggest that constituent lipid molecular species (formed via different pathways) are associated with the specialized structure and function of the chloroplast membrane systems.