ISSN:0032-0889    

DOI:10.1104/pp.104.1.1

出版商:American Society of Plant Biologists    

年代:1994

数据来源: ASPB

摘要:

Phloem unloading and post-phloem transport in developing wheat (Triticum aestivum L.) grains were investigated by perfusing the endosperm cavities of attached grains. Relative unloading ratio (RUR) and the rate of sucrose release into the endosperm cavity (SRR) were calculated, respectively, from 14C import and from sucrose washout from the cavity. RUR and SRR continued at or near in vivo rates over a wide range of cavity sap osmolality (90 to approximately 500 milliosmolal) and sucrose concentration (14–430 mM) and for long times (29 h). These are much greater ranges than have been observed for the endosperm cavity in vivo (230–300 milliosmolal, and 40–120 mM, respectively), indicating that neither the cavity sap osmolality nor sucrose concentration are controlling factors for the rate of assimilate import into the cavity. The maintenance of in vivo transport rates over a wide range of conditions strongly implicates the role of transport processes within the maternal tissues of the wheat grain, rather than activities of the embryo or endosperm, in determining the rate of assimilate import into the grain. RUR was decreased by high concentrations of sucrose and sorbitol, but not of mannitol. By plasmolyzing some chalazal cells, sorbitol appeared to block symplastic transport across the crease tissues, but neither sucrose nor mannitol caused plasmolysis in maternal tissues of attached grains. The inhibition of RUR by KCN and carbonyl cyanide m-chlorophenyl (CCCP) and the continued import of sucrose into grains against its concentration gradient suggest that solute movement into the endosperm cavity might occur by active membrane transport. However, the evidence is weak, since KCN and CCCP appeared to act primarily on some aspect of symplastic (i.e. nonmembrane) transport. Also, sucrose could move from the endosperm cavity into the maternal tissues (i.e. opposite to the normal direction of sucrose movement), suggesting that transmembrane movement in the nucellus may be a reversible process. Pressure-driven flow into the grain could account for movement against a concentration gra

ISSN:0032-0889    

DOI:10.1104/pp.104.1.7

出版商:American Society of Plant Biologists    

年代:1994

数据来源: ASPB

摘要:

Various polar fluorescent tracers were used to characterize the pathways for apoplastic and symplastic transport in the“crease tissues”(i.e. the vascular strand, chalaza, nucellus, and adjacent pericarp) of developing wheat (Triticum aestivum L.) grains. With mostly minor exceptions, the results strongly support existing views of phloem unloading and post-phloem transport pathways in the crease. Apoplastic movement of Lucifer yellow CH (LYCH) from the endosperm cavity into the crease was virtually blocked in the chalazal cell walls before reaching the vascular tissue. However, LYCH could move slowly along the cell wall pathway from the chalaza into the vascular parenchyma. Slow uptake of LYCH into nucellar cell cytoplasm was observed, but no subsequent symplastic movement occurred. Carboxyfluorescein (CF) imported into attached grains moved symplastically from the phloem across the chalaza and into the nucellus, but was not released from the nucellus. In addition, CF moved in the opposite direction (nucellus to vascular parenchyma) in attached grains. Thus, the post-phloem symplastic pathway can accommodate bidirectional transport even when there is an intense net assimilate flux in one direction. When fresh sections of the crease were placed in fluorochrome solutions (e.g. LYCH or pyrene trisulfonate), dye was rapidly absorbed into intact cells, apparently via unsealed plasmodesmata. Uptake was not visibly reduced by cold or by respiratory inhibitors, but was greatly reduced by plasmolysis. Once absorbed, the dye moved intercellularly via the symplast. Based on this finding, a size-graded series of fluorescein-labeled dextrans was used to estimate the size-exclusion limits (SEL) for the post-phloem symplastic pathway. In most, and perhaps all, cells of the crease tissues except for the pericarp, the molecular diameter for the SEL was about 6.2 nm. The SEL in much of the vascular parenchyma may be smaller, but it is still at least 3.6 nm. Channel diameters would likely be about 1 nm larger, or about 4.5 to 7.0 nm in the vascular parenchyma and 7.0 nm elsewhere. These dimensions are substantially larger than those for“conventional”symplastic connections (about 3 nm), and would have a greater than proportionate effect on the per channel diffusive and hydraulic conductivities of the pathway. Thus, relatively small and probably ultrastructurally undetectable adjustments in plasmodesmatal structure may be sufficient to account for assimilate flux through the crease s

ISSN:0032-0889    

DOI:10.1104/pp.104.1.17

出版商:American Society of Plant Biologists    

年代:1994

数据来源: ASPB

摘要:

Plum (Prunus domestica) seeds, which contain the cyanogenic diglucoside (R)-amygdalin and lesser amounts of the corresponding monoglucoside (R)-prunasin, release the respiratory toxin HCN upon tissue disruption. Amygdalin hydrolase (AH) and prunasin hydrolase (PH), two specific [beta]-glucosidases responsible for hydrolysis of these glucosides, were purified to near homogeneity by concanavalin A-Sepharose 4B and carboxymethyl-cellulose chromatography. Both proteins appear as polypeptides with molecular masses of 60 kD upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but they exhibit different isoelectric points (PH, 5.6–6.0; AH, 7.8–8.2). AH and PH were localized within mature plum seeds by tissue printing, histochemistry, and silver-enhanced immunogold labeling. As was previously shown in black cherry (Prunus serotina) seeds (E.Swain, C.P. Li, J.E. Poulton [1992] Plant Physiol 100: 291–300), AH and PH are restricted to protein bodies of specific procambial cells and are absent from the cotyledonary parenchyma, bundle sheath, and endosperm cells. In contrast, the cyanogenic glycosides in both plum and black cherry seeds, which were detected by tissue printing, occur solely in the cotyledonary parenchyma and are absent from the procambium and endosperm. It is concluded that tissue level compartmentation prevents large-scale cyanoglycoside hydrolysis in intact Prunus

ISSN:0032-0889    

DOI:10.1104/pp.104.1.29

出版商:American Society of Plant Biologists    

年代:1994

数据来源: ASPB

摘要:

A rapid, efficient, and reproducible system to generate large numbers of independently transformed, self-fertile, transgenic barley (Hordeum vulgare L.) plants is described. Immature zygotic embryos, young callus, and microspore-derived embryos were bombarded with a plasmid containing bar and uidA either alone or in combination with another plasmid containing a barley yellow dwarf virus coat protein (BYDVcp) gene. A total of 91 independent bialaphos-resistant callus lines expressed functional phosphinothricin acetyltransferase, the product of bar. Integration of bar was confirmed by DNA hybridization in the 67 lines analyzed. Co-transformation frequencies of 84 and 85% were determined for the two linked genes (bar and uidA) and for two unlinked genes (bar and the BYDVcp gene), respectively. More than 500 green, fertile, transgenic plants were regenerated from 36 transformed callus lines on bialaphos-containing medium; albino plants only were regenerated from 41 lines. T0 plants in 25 lines (three plants per line) were analyzed by DNA hybridization, and all contained bar. Most contained the same integration patterns for the introduced genes (bar, uidA, and the BYDVcp gene) as their parental callus lines. Transmission of the genes to T1 progeny was confirmed in the five families analyzed by DNA hybridization. A germination test of immature T1 embryos on bialaphos-containing medium was useful for selecting individuals that were actively expressing bar, although this was not a good indicator of the presence or absence of bar. Expression of bar in some progeny plants was indicated by resistance to the herbicide Basta. The T1 plants were in soil approximately 7 months after bombardment of the immature embryo.

ISSN:0032-0889    

DOI:10.1104/pp.104.1.37

出版商:American Society of Plant Biologists    

年代:1994

数据来源: ASPB

摘要:

Fruit removal for 5 weeks after flowering increased acid phosphatase activity 10-fold in soybean (Glycine max L. Merr. Var Hobbit) leaves compared with normal seed-pod-bearing plants. The major acid phosphatase activity in leaves was purified over 2700-fold, yielding a single polypeptide of 51 kD with a specific activity of 1353 units/mg protein using p-nitrophenylphosphate as the substrate. Isoelectric focusing demonstrated that the purified protein co-migrated with a majority of the activity that increased in leaves following seed-pod removal. Immunoblot analysis demonstrated that at least part of the increased activity was due to an increased abundance of the phosphatase protein. In situ enzyme activity staining localized most of the total phosphatase activity to vascular tissues, the leaf paraveinal mesophyll cell layer, and the lower epidermis. This distribution and the response to seed-pod removal paralleled previous results for soybean vegetative storage protein (VSP) [alpha] and [beta]. However, in a native polyacrylamide gel the VSP detected by immunological staining of electrophoretically transferred protein did not migrate with the majority of the phosphatase activity. Fractionation of crude leaf protein on concanavalin A-Sepharose yielded a fraction containing 97% of the total VSP but only 0.1% of the total acid phosphatase activity.

ISSN:0032-0889    

DOI:10.1104/pp.104.1.49

出版商:American Society of Plant Biologists    

年代:1994

数据来源: ASPB

摘要:

Tomato (Lycopersicon esculentum L.) plants were sprayed with aqueous solutions of isomers of aminobutyric acid and were either analyzed for the accumulation of pathogenesis-related (PR) proteins or challenged with the late blight fungal agent Phytophthora infestans. The [beta] isomer of aminobutyric acid induced the accumulation of high levels of three proteins: P14a, [beta]-1,3 glucanase, and chitinase. These proteins either did not accumulate or accumulated to a much lower level in [alpha]- or [gamma]-aminobutyric acid-treated plants. Plants pretreated with [alpha]-, [beta]-, and [gamma]-aminobutyric acid were protected up to 11 d to an extent of 35, 92, and 6%, respectively, against a challenge infection with P. infestans. Protection by [beta]-aminobutyric acid was afforded against the blight even when the chemical was applied 1 d postinoculation. Examination of ethylene evolution showed that [alpha]-aminobutyric acid induced the production of 3-fold higher levels of ethylene compared with [beta]-aminobutyric acid, whereas [gamma]-aminobutyric acid induced no ethylene production. In addition, silver thiosulfate, a potent inhibitor of ethylene action, did not abolish the resistance induced by [beta]-aminobutyric acid. The results are consistent with the possibility that [beta]-aminobutyric acid protects tomato foliage against the late blight disease by a mechanism that is not mediated by ethylene and that PR proteins can be involved in induced resistance.

ISSN:0032-0889    

DOI:10.1104/pp.104.1.59

出版商:American Society of Plant Biologists    

年代:1994

数据来源: ASPB

摘要:

Parsley (Petroselinum crispum L.) is known to respond to ultraviolet irradiation by the synthesis of flavone glycosides, whereas fungal or elicitor stress leads to the synthesis of furanocoumarin phytoalexins. We tested how these defensive pathways are affected by a single ozone treatment (200 nL L-1; 10 h). Assays were performed at the levels of transcripts, for enzyme activities, and for secondary products. The most rapid transcript accumulation was maximal at 3 h, whereas flavone glycosides and furanocoumarins were maximally induced at 12 and 24 h, respectively, after the start of ozone treatment. Ozone acted as a cross-inducer because the two distinct pathways were simultaneously induced. These results are consistent with the previously observed ozone induction of fungal and viral defense reactions in tobacco, spruce, and pine.

ISSN:0032-0889    

DOI:10.1104/pp.104.1.67

出版商:American Society of Plant Biologists    

年代:1994

数据来源: ASPB

摘要:

Cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195) isoforms were purified from the periderm (containing both suberized and lignified cell layers) of Eucalyptus gunnii Hook stems. Two isoforms (CAD 1P and CAD 2P) were initially characterized, and the major form, CAD 2P, was resolved into three further isoforms by ion-exchange chromatography. Crude extracts contained two aliphatic alcohol dehydrogenases (ADH) and one aromatic ADH, which was later resolved into two further isoforms. Aliphatic ADHs did not use hydroxycinnamyl alcohols as substrates, whereas both aromatic ADH isoforms used coniferyl and sinapyl alcohol as substrates but with a much lower specific activity when compared with benzyl alcohol. The minor form, CAD 1P, was a monomer with a molecular weight of 34,000 that did not co-elute with either aromatic or aliphatic ADH activity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blot analysis demonstrated that this protein was very similar to another CAD isoform purified from Eucalyptus xylem tissue. CAD 2P had a native molecular weight of approximately 84,000 and was a dimer consisting of two heterogenous subunits (with molecular weights of 42,000 and 44,000). These subunits were differentially combined to give the heterodimer and two homodimers. SDS-PAGE, western blots, and nondenaturing PAGE indicated that the CAD 2P heterodimer was very similar to the main CAD isoform previously purified in our laboratory from differentiating xylem tissue of E. gunnii (D. Goffner, I. Joffroy, J. Grima-Pettenati, C. Halpin, M.E. Knight, W. Schuch, A.M. Boudet [1992] Planta 188: 48–53). Kinetic data indicated that the different CAD 2P isoforms may be implicated in the preferential production of different monolignols used in the synthesis of lignin and/or suberi

ISSN:0032-0889    

DOI:10.1104/pp.104.1.75

出版商:American Society of Plant Biologists    

年代:1994

数据来源: ASPB

摘要:

The effect of boron deficiency on symbiotic nitrogen fixation in pea (Pisum sativum) was examined. The absence of boron in the culture medium resulted in a decrease of the number of nodules and an alteration of nodule development leading to an inhibition of nitrogenase activity. Examination of boron-deficient nodules showed dramatic changes in cell walls and in both peribacteroid and infection thread membranes, suggesting a role for boron in the stability of these structures. These results indicate that boron is a requirement for normal nodule development and functionality.

ISSN:0032-0889    

DOI:10.1104/pp.104.1.85

出版商:American Society of Plant Biologists    

年代:1994

数据来源: ASPB