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491.
Glendon D. Ascough John E. Erwin Johannes van Staden 《Plant Cell, Tissue and Organ Culture》2008,95(3):275-283
Storage organ induction in vitro can limit the loss of plants during acclimatisation, and can substantially reduce the time
to flower following acclimatisation. An initial experiment lasting 3 months showed that of the four Watsonia species investigated, only Watsonia vanderspuyiae was capable of consistent corm formation. Consequently, a second study investigating light, temperature (10, 15, 20 and 25°C),
carbohydrates (sucrose at 3, 6, 9 or 12%) and plant growth regulators [α-naphthalene acetic acid (NAA), N
6-benzylaminopurine (BA), abscisic acid (ABA), gibberellic acid 3 (GA3), paclobutrazol (PAC) and methyl jasmonate (MeJa)], lasting 6 months, was performed. Abnormal corms were produced by W. lepida in response to ABA, but normal corms formed at lower temperatures (10 and 20°C). In contrast, corms were produced in most
treatments of W. vanderspuyiae, with BA, PAC and ABA being the only treatments that inhibited corm induction. By examining the product of the proportion
corm induction multiplied by corm mass, four treatments superior to the control (20°C, 1 mg l−1 GA3, 6% sucrose and continuous light) were selected for a factorial design experiment in W. vanderspuyiae. After 3 months, treatments were ranked according to their product. The best four combinations of these four factors all
contained GA3 and were incubated at 20°C, suggesting synergistic interactions between gibberellins and reduced temperature. 相似文献
492.
The gene CYTOKININ INDEPENDENT-1 (CKI-1), previously isolated by enhancer trap screening, has been hypothesised to play a role in cytokinin perception. Alternative hypotheses suggest that it is required for the production of cytokinins or that it has no direct role in cytokinin signalling but simply interferes with the pathway when overexpressed. These hypotheses were investigated by producing transgenic Arabidopsis plants expressing CKI-1 cDNA in antisense orientation. In standard conditions, the phenotype of the plants was similar to wild type. Significantly higher amounts of the free base and riboside forms of cytokinin and lower amounts of membrane-impermeable cytokinins were found in the antisense lines. This supports the hypothesis that CKI-1 is involved in cytokinin perception and demonstrates the existence of a feedback loop altering cytokinin metabolism in response to the level of receptor abundance. An elevation in the content of free bases and ribosides of zeatin and isopentenyladenine, along with a reduction in the content of ribotide forms, suggests that a cytokinin ribotide 5'-ribonucleotidase may be a site at which CKI-1 exerts feedback control. When seed homozygous for the transgene was germinated on medium with reduced total mineral nutrient levels, the cotyledons of seedlings with reduced levels of CKI-1 failed to expand and green, and vegetative growth was inhibited. A similar phenotype was observed on low-phosphate media, suggesting that this failure resulted from an interaction between phosphate and cytokinins. 相似文献
493.
Does NO play a role in cytokinin signal transduction? 总被引:1,自引:0,他引:1
494.
L. Messchendorp G.J.Z. Gols J.J.A. van Loon 《Entomologia Experimentalis et Applicata》2000,95(3):217-227
We tested 11 analogous synthetic drimane antifeedant compounds for their feeding inhibiting effects on larvae of the large white butterfly Pieris brassicae L. (Lepidoptera: Pieridae) in no-choice tests on the host plant Brassica oleracea L. Furthermore, we observed larval feeding behaviour in no-choice tests to analyze temporal effects of five drimanes. The results show that the five analogous antifeedants differentially influence feeding behaviour and locomotion activity. Warburganal and polygodial are most likely sensory mediated antifeedants. Habituation to these compounds occurs soon after the onset of the tests (i.e., within 0.5–1.5 h). Compound 5 and confertifolin are probably not direct, sensory mediated antifeedants. After 0.5–1.5 h of exposure, these compounds inhibit not only feeding, but also locomotion behaviour, indicating postingestive, toxic effects. Isodrimenin inhibits feeding from the onset of the test and is probably a sensory mediated antifeedant. No habituation occurs to this compound, indicating that isodrimenin is either a very strong antifeedant or that it additionally has postingestive, toxic effects. Topical application of the drimanes on the larval cuticle revealed feeding inhibiting effects, but these could not be related to the occurrence of postingestive feeding inhibiting effects, indicating that this method is inappropriate to show possible postingestive effects of drimanes in P. brassicae. In conclusion, the behavioural observations performed in this research indicate that analogous drimanes inhibit feeding by P. brassicae larvae through multiple mechanisms of action. The results show that, when developing a structure activity relationship (SAR) for a series of antifeedants, it is important to distinguish the mode of action which underlies inhibition of feeding. 相似文献
495.
We present efficient protocols for the regeneration of fertile plants from corm explants of Hypoxis hemerocallidea Fisch. & C. A. Mey. landrace Gaza, either by direct multiple shoot formation or via shoot organogenesis from corm-derived calluses. The regeneration efficiency depended on plant growth regulator concentrations
and combinations. Multiple direct shoot formation with high frequency (100% with 5–8 shoots/explant) was obtained on a basal
medium (BM) supplemented with 3 mg/l kinetin (BM1). However, efficient indirect regeneration occurred when corm explants were
first plated on callus induction medium (BM2) with high kinetin (3 mg/l) and naphthalene acetic acid (NAA 1 mg/l), and then
transferred to shoot inducing medium (BM3) containing BA (1.5 mg/l) and NAA (0.5 mg/l). Shoot regeneration frequency was 100%
and 30–35 shoots per explant were obtained. The regenerated shoots were rooted on a root inducing medium (BM4) containing
NAA (0.1 mg/l). Rooted plantlets were transferred to the greenhouse. The regenerants were morphologically normal and fertile.
Flow cytometric analyses and chloroplast counts of guard cells suggested that the regenerants were diploid. Efficient cloning
protocols described here, have the potential not only to substantially reduce the pressure on natural populations but also
for wider biotechnological applications of Hypoxis hemerocallidea—an endangered medicinal plant. 相似文献
496.
Gu R Zhao L Zhang Y Chen X Bao J Zhao J Wang Z Fu J Liu T Wang J Wang G 《Plant cell reports》2006,25(11):1157-1165
The β-glucosidase gene of maize (ZmGLU1) was suggested to hydrolyze cytokinin-conjugate and release free cytokinin during plant growth and development. A clone containing the upstream region of ZmGLU1 was isolated and sequenced from a maize genomic library. The full-length ZmGLU1 promoter and a series of its 5′ deletions were fused to the beta-glucuronidase (GUS) reporter gene and transferred into tobacco. The GUS activity of transgenic plants was assayed at various developmental stages. The results showed that ZmGLU1 promoter-driven GUS gene had the highest expression level in the roots and that the expression of GUS gene declined during seed maturation and down to the lowest level in mature seeds. The ZmGLU1 promoter-driven GUS expression increased during seed germination, reaching a peak on day 11. The results also showed that this promoter could be inhibited by 6-BA, trans-zeatin, and NAA, but was not affected by GA3, ABA, SA, cold, salt, drought, and submergence treatments. The histochemical staining revealed that GUS activity was located in vigorous cell division zones with dominant staining associated with vascular tissues. Deletion analysis showed that the promoter contained a putative leaf-specific and stem-specific negative regulative element and two putative enhancers. 相似文献
497.
David Kopečný Pierre Briozzo Hana Popelková Marek Šebela Radka Končitíková Lukáš Spíchal Jaroslav Nisler Catherine Madzak Ivo Frébort Michel Laloue Nicole Houba-Hérin 《Biochimie》2010
Cytokinin oxidase/dehydrogenase (CKO) is a flavoenzyme, which irreversibly degrades the plant hormones cytokinins and thereby participates in their homeostasis. Several synthetic cytokinins including urea derivatives are known CKO inhibitors but structural data explaining enzyme–inhibitor interactions are lacking. Thus, an inhibitory study with numerous urea derivatives was undertaken using the maize enzyme (ZmCKO1) and the crystal structure of ZmCKO1 in a complex with N-(2-chloro-pyridin-4-yl)-N′-phenylurea (CPPU) was solved. CPPU binds in a planar conformation and competes for the same binding site with natural substrates like N6-(2-isopentenyl)adenine (iP) and zeatin (Z). Nitrogens at the urea backbone are hydrogen bonded to the putative active site base Asp169. Subsequently, site-directed mutagenesis of L492 and E381 residues involved in the inhibitor binding was performed. The crystal structures of L492A mutant in a complex with CPPU and N-(2-chloro-pyridin-4-yl)-N′-benzylurea (CPBU) were solved and confirm the importance of a stacking interaction between the 2-chloro-4-pyridinyl ring of the inhibitor and the isoalloxazine ring of the FAD cofactor. Amino derivatives like N-(2-amino-pyridin-4-yl)-N′-phenylurea (APPU) inhibited ZmCKO1 more efficiently than CPPU, as opposed to the inhibition of E381A/S mutants, emphasizing the importance of this residue for inhibitor binding. As highly specific CKO inhibitors without undesired side effects are of major interest for physiological studies, all studied compounds were further analyzed for cytokinin activity in the Amaranthus bioassay and for binding to the Arabidopsis cytokinin receptors AHK3 and AHK4. By contrast to CPPU itself, APPU and several benzylureas bind only negligibly to the receptors and exhibit weak cytokinin activity. 相似文献
498.
499.
Irina?Vaseva-GemishevaEmail author Iskren?Sergiev Desislava?Todorova Vera?Alexieva Elena?Stanoeva Viktoria?Lachkova Emanuil?Karanov 《Plant Growth Regulation》2005,46(3):193-197
The effect of strong and weak cytokinin antagonists, belonging to the groups of triazolo[4,5-d]pyrimidines (TP), and pyridyl-phenylurea
derivatives (PU), on cytokinin oxidase/dehydrogenase activity (CKX) in the tissues of young pea plants was studied. Tested
anticytokinins, with the exception of the most efficient one – PU-1, were able to promote increased CKX activity in roots,
when applied alone, but they had no significant influence on the enzymatic activity in leaves. N6-benzyladenine (BA) and 1-(2-chloropyridin-4-yl)-3-phenylurea (CPPU) provoked strong increase in CKX activity in roots, while
in leaves considerable inhibition of enzymatic activity was observed. Different types of anticytokinins exhibited diverse
preference towards taking off the action of purine and phenylurea cytokinins over CKX activity. 相似文献
500.
Insects are capable of detecting, and discriminating between, a very large number of odours. The biological relevance of many
of those odours, particularly those related to food, must first be learned. Given that the number of sensory receptors and
antennal lobe (AL) glomeruli is limited relative to the number of odours that must be detectable, this ability implies that
the olfactory system makes use of a combinatorial coding scheme whereby each sensory cell or AL projection neuron can participate
in coding for several different odours. An important step in understanding this coding scheme is to behaviourally quantify
the degree to which sets of odours are discriminable. Here we evaluate odour discriminability in the fruit fly,Drosophila melanogaster, by first conditioning individual flies to not respond to any of several odourants using a nonassociative conditioning protocol
(habituation). We show that flies habituate unconditioned leg movement responses to both mechanosensory and olfactory stimulation
over 25 unreinforceed trials. Habituation is retained for at least 2 h and is subject to dishabituation. Finally, we test
the degree to which the conditioned response generalizes to other odourants based on molecular features of the odourants (e.g.
carbon chain length and the presence of a target functional group). These tests reveal predictable generalization gradients
across these molecular features. These data substantiate the claim that these features are relevant coding dimensions in the
fruit fly olfactory system, as has been shown for other insect and vertebrate species. 相似文献