膜荚黄芪与蒙古黄芪幼苗的光能利用及其耐光性研究

以盆栽膜荚黄芪和蒙古黄芪幼苗为试验材料,测量2种黄芪叶片的光合速率、叶绿素荧光参数、光能利用率及耐光性等指标的日变化,以探讨它们的光能利用、热耗散以及耐光性差异.结果表明:(1)随着太阳光合有效辐射的日变化进程推进,2种黄芪的初始荧光(F0)、非光化学淬灭(NPQ)、PSⅡ调节性能量耗散量子产最(YNPQ)先升高后降低...     

Astragaloside IV and polysaccharide production by hairy roots of Astragalus membranaceus in bioreactors

Hairy roots of Astragalus membranaceus were grown in bioreactors up to 30 l for 20 d. Cultures from a 30 l airlift bioreactor gave 11.5 g l dry wt with 1.4 mg g^–1 astragaloside IV, similar to cultures from 250 ml and 1 l flasks, but greater than yields from a 10 l bioreactor (dry wt 9.4 g l^–1, astragaloside IV 0.9 mg g^–1). Polysaccharide yields were similar amongst the different bioreactors (range 25–32 mg g^–1). The active constituent content of the cells approached that of plant extracts, indicating that large scale hairy root cultures of A. membranaceus has the potential to provide an alternative to plant crops without compromising yield or pharmacological potential.     

Phytochrome-induced flavonoid biosynthesis in mustard (Sinapis alba L.) cotyledons. Enzymic control and differential regulation of anthocyanin and quercetin formation

Phytochrome-induced increases in enzyme activities for phenylalanine ammonia-lyase (EC 4.3.1.5) and chalcone isomerase (EC 5.5.1.6), and in amounts of the related end products, anthocyanin and the flavonol, quercetin, were measured in cotyledons of mustard (Sinapis alba L.). There was no correlation between the activities of these enzymes and the rate of anthocyanin accumulation; however, some correlation was found with the quercetin accumulation rate. Since anthocyanin and flavonol accumulation is spatially separated in mustard (flavonols in the upper epidermis, anthocyanin in the lower epidermis), it was possible to measure anthocyanin-associated phenylalanine ammonia-lyase independently. This activity correlated well with the accumulation rate for anthocyanin during the first few hours after induction. The phytochrome effect on anthocyanin formation differed from that on quercetin formation: anthocyanin was strongly induced by continuous far-red light and by both continuous red light and red light pulses, whereas quercetin was only effectively induced by continuous far-red light.Abbreviations CHI chalcone isomerase - PAL phenylalanine ammonia-lyase     

Extension-growth responses and expression of flavonoid biosynthesis genes in the Arabidopsis hy4 mutant

The hy4 mutant of Arabidopsisthaliana(L.) Heynh. was previously shown to be impaired in the suppression of hypocotyl extension specifically by blue light. We report here that hy4 is altered in a range of blue-light-mediated extension-growth responses in various organs in seedlings and mature plants: it shows greater length of bolted stems, increased petiole extension and increased leaf width and area in blue light compared to the wild type. The hy4 mutant shows decreased cotyledon expansion in both red and blue light compared to the wild type. Anthocyanin formation and the expression of several flavonoid biosynthesis genes is stimulated by blue light in the wild type but to a much lower extent in hy4. The results indicate that the HY4 gene product is concerned with the perception of blue light in a range of extension-growth and gene-expression responses in Arabidopsis.Abbreviations DFR dihydroflavonol reductase - CHS chalcone synthase - CHI chalcone isomeraseWe thank the UK Agricultural and Food Research Council for supporting this work through the award of a research grant to G.I.J. We are grateful to Robert Brown for excellent technical assistance and Drs B.W. Shirley (Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, USA), C.D. Silflow (Department of Genetics and Cell Biology, University of Minnesota, St. Paul, USA) and I.E. Somssich (Department of Biochemistry, Max-Planck-Institut, Köln, Germany) for providing plasmid DNA.     

Inhibition of flavonoid biosynthesis by gibberellic acid in cell suspension cultures of Daucus carota L.

In carrot cells (Daucus carota L.), cultured in the presence of gibberellic acid, anthocyanin synthesis is blocked at the level of chalcone synthase. By feeding suitable precursors for anthocyanins (naringenin, eriodictyol, dihydroquercetin) biosynthesis of cyanidin glycosides can be restored. After addition of these substrates to the culture medium in the presence of gibberellic acid, the activity of chalcone synthase remained as low as in the control without precursors. The highest increase in anthocyanin content was achieved using dihydroquercetin as the added precursor. The time course of this supplementation showed a rapid response; within 4 h a substantial increase in anthocyanin could be observed. In contranst, the flavonol quercetin is not a precursor for cyanidin. The fact that naringenin was also accepted for cyanidin synthesis leads to the conclusion that hydroxylation in 3-position of ring B in Daucus carota takes place at the flavonoid stage.Abbreviations CHI Chalcone isomerase - CHS chalcone synthase - DMSO dimethylsulfoxide - GA₃ gibberellic acid - PAL phenylalanine ammonia-lyase     

First environmental isolation of Cryptococcus neoformans var. neoformans and var. gatti from the Gharbia Governorate,Egypt

Flowers from two Eucalyptus camaldulensis trees in the Qutur area and one tree from the Tanta area yielded three isolates of Cryptococcus neoformans var. gattii. Pigeon and sparrow droppings were also investigated for the occurrence of C. neoformans within the study area. Ninety five isolates of the neoformans variety of C. neoformans were recovered from 550 samples of avian droppings. This revised version was published online in October 2005 with corrections to the Cover Date.     

Water deficits accelerate ripening and induce changes in gene expression regulating flavonoid biosynthesis in grape berries

Water deficits consistently promote higher concentrations of anthocyanins in red winegrapes and their wines. However, controversy remains as to whether there is any direct effect on berry metabolism other than inhibition of growth. Early (ED) and late (LD) season water deficits, applied before or after the onset of ripening (veraison), were imposed on field grown Vitis vinifera “Cabernet Sauvignon”, and the responses of gene expression in the flavonoid pathway and their corresponding metabolites were determined. ED accelerated sugar accumulation and the onset of anthocyanin synthesis. Both ED and LD increased anthocyanin accumulation after veraison. Expression profiling revealed that the increased anthocyanin accumulation resulted from earlier and greater expression of the genes controlling flux through the anthocyanin biosynthetic pathway, including F3H, DFR, UFGT and GST. Increases in total anthocyanins resulted predominantly from an increase of 3′4′5′-hydroxylated forms through the differential regulation of F3′H and F3′5′H. There were limited effects on proanthocyanidin, other flavonols, and on expression of genes committed to their synthesis. These results demonstrate that manipulation of abiotic stress through applied water deficits not only modulates compositional changes during berry ripening, but also alters the timing of particular aspects of the ripening process.     

氮离子注入对蒙古黄芪多倍体诱导的影响

利用二倍体蒙古黄芪种子为材料,以低能氮离子束为诱变源,将化学诱导与物理诱变相结合,探索出一套高效的多倍体诱导新方法。研究结果表明：氮离子注入种子后表现出明显的生物学效应;氮离子注入与秋水仙素联合诱导黄芪多倍体的效果很明显。氮离子注入剂量为2.6×10¹⁶ N⁺/cm²,秋水仙素浓度为100 mg·L^-1,培养5 d诱导率最高为44.4%;氮离子注入剂量为5.2×10¹⁶ N⁺/cm², 秋水仙素浓度为150 mg·L^-1,培养10d的诱导率最高为46.2%;二者均高于对照组秋水仙素浓度为100 mg·L^-1培养15 d的最高诱导率13.9%。利用细胞染色体计数鉴定多倍体为四倍体。     

Tissue-distribution of secondary phenolic biosynthesis in developing primary leaves of Avena sativa L.

Primary leaves of oats (Avena sativa L.) have been used to study the integration of secondary phenolic metabolism into organ differentiation and development. In particular, the tissue-specific distribution of products and enzymes involved in their biosynthesis has been investigated. C-Glucosylflavones along with minor amounts of hydroxycinnamic-acid esters constitute the soluble phenolic compounds in these leaves. In addition, considerable amounts of insoluble products such as lignin and wall-bound ferulic-acid esters are formed. The tissue-specific activities of seven enzymes were determined in different stages of leaf growth. The rate-limiting enzyme of flavonoid biosynthesis in this system, chalcone synthase, together with chalcone isomerase (EC 5.5.1.6) and the terminal enzymes of the vitexin and isovitexin branches of the pathway (a flavonoid O-methyltransferase and an isovitexin arabinosyltransferase) are located in the leaf mesophyll. Since the flavonoids accumulate predominantly (up to 70%) in both epidermal layers, an intercellular transport of products is postulated. In contrast to the flavonoid enzymes, L-phenylalanine ammonia-lyase (EC 4.3.1.5), 4-coumarate: CoA ligase (EC 6.2.1.12), and S-adenosyl-L-methionine: caffeate 3-O-methyltransferase (EC 2.1.1.-), all involved in general phenylpropanoid metabolism, showed highest activities in the basal leaf region as well as in the epidermis and the vascular bundles. We suggest that these latter enzymes participate mainly in the biosynthesis of non-flavonoid phenolic products, such as lignin in the xylem tissue and wall-bound hydroxycinnamic acid-esters in epidermal, phloem, and sclerenchyma tissues.Abbreviations CHI chalcone isomerase - CHS chalcone synthase - 4CL 4-coumarate: CoA ligase - CMT S-adenosyl-L-methionine:caffeate 3-O-methyltransferase - FMT S-adenosyl-L-methionine:vitexin 2-O-rhamnoside 7-O-methyltransferase - HPLC high-performance liquid chromatography - IAT uridine 5-diphosphate L-arabinose:isovitexin 2-O-arabinosyltransferase - PAL L-phenylalanine ammonia-lyase     

Isolation and genetic mapping of a Coffea canephora phenylalanine ammonia-lyase gene (CcPAL1) and its involvement in the accumulation of caffeoyl quinic acids

Biosynthesis of caffeoylquinic acids occurs via the phenylpropanoid pathway in which the phenylalanine ammonia-lyase (PAL) acts as a key-control enzyme. A full-length cDNA (pF6), corresponding to a PAL gene (CcPAL1), was isolated by screening a Coffea canephora fruit cDNA library and its corresponding genomic sequence was characterized. Amplification of total DNA from seven Coffea species revealed differences in intronic length. This interspecific polymorphism was used to locate the gene on a genetic map established for a backcross progeny between Coffea pseudozanguebariae and C. dewevrei. The CcPAL1 gene was found on the same linkage group, but genetically independent, as a caffeoyl-coenzyme A-O-methyltransferase gene, another gene intervening in the phenylpropanoid pathway. In the same backcross, a lower caffeoylquinic acid content was observed in seeds harvested from plants harbouring the C. pseudozanguebariae CcPAL1 allele. Involvement of the CcPAL1 allelic form in the differential accumulation of caffeoylquinic acids in coffee green beans is then discussed.     

Rapid induction of ethylene biosynthesis in cultured parsley cells by fungal elicitor and its relationship to the induction of phenylalanine ammonia-lyase

The biosynthesis of ethylene was examined in suspension-cultured cells of parsley (Petroselinum hortense) treated with an elicitor from cell walls of Phytophthora megasperma. Untreated cells contained 50 nmol g^-1 of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), and produced ethylene at a rate of about 0.5 nmol g^-1 h^-1. Within 2 h after addition of elicitor to the culture medium, the cells started to produce more ethylene and accumulated more ACC. Exogenously added ACC did not increase the rate of ethylene production in control or elicitor-treated cells, indicating that the enzyme converting ACC to ethylene was limiting in both cases. The first enzyme in ethylene biosynthesis, ACC synthase, was very rapidly and transiently induced by the elicitor treatment. Its activity increased more than tenfold within 60 min. Density labelling with ²H₂O showed that this increase was caused by the denovo synthesis of the enzyme protein. Cordycepin and actinomycin D did not affect the induction of ACC synthase, indicating that the synthesis of new mRNA was not required. The peak of ACC-synthase activity preceded the maximal phenylalanine ammonia-lyase (PAL) activity by several hours. Exogenously supplied ethylene or ACC did not induce PAL. However, aminoethoxyvinylglycine, an inhibitor of ACC synthase, suppressed the rise in ethylene production in elicitor-treated cells and partially inhibited the induction of PAL. Exogenously supplied ACC reversed this inhibition. It is concluded that induction of the ethylene biosynthetic pathway is a very early symptom of elicitor action. Although ethylene alone is not a sufficient signal for PAL induction, the enhanced activity of ACC synthase and the ethylene biosynthetic pathway may be important for the subsequent induction of PAL.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglycine - PAL phenylalanine ammonia-lyase     

Neolignan and flavonoid glycosides in Juniperus communis var. depressa

Two neolignan glycosides (junipercomnosides A and B) were isolated from aerial parts of Juniperus communis var. depressa along with two known neolignan glycosides and seven flavonoid glycosides. The structures of the isolated compounds were determined by spectral analysis, in particular by 2D-NMR analysis. The significance of distribution of flavonoids in the chemotaxonomy of genus Juniperus was also discussed.     

Comparative study of leaf carbon gain in saplings ofThujopsis dolabrata var.hondai andQuercus mongolica var.grosseserrata in a cool-temperate deciduous forest

Seasonal courses of leaf CO₂ gas exchange in a growing season were examined in saplings ofThujopsis dolabrata var.hondai andQuercus mongolica var.grosseserrata in a cool temperate deciduous forest. Between the two tree species there were no large differences in the light compensation point of leaf photosynthesis, except for the season of new leaf expansion. However, light-saturated rates of net photosynthesis were obviously high inT. dolabrata var.hondai. EvergreenT. dolabrata var.hondai saplings had large photosynthetic production in two seasons, before the emergence of new foliage and after foliage fall of the overstory deciduous trees, because of the significantly high solar radiant energy penetrating under the forest canopy during the seasons. Saplings of deciduousQ. mongolica var.grosseserrata were heavily shaded throughout the growing season by foliage of the overstory trees, which resulted in a low daily surplus production. The annual surplus production of leaves in the growing season was estimated to be 2300 mmol CO₂ m⁻² inT. dolabrata var.hondai and −100 mmol CO₂ m⁻², slightly negative, inQ. mongolica var.grosseserrata. These results supported the high survivability ofT. dolabrata var.hondai saplings and the high mortality ofQ. mongolica var.grosseserrata in the deciduous forest.