ISSN:0032-0889    

DOI:10.1104/pp.110.1.1

出版商:American Society of Plant Biologists    

年代:1996

数据来源: ASPB

ISSN:0032-0889    

DOI:10.1104/pp.110.1.3

出版商:American Society of Plant Biologists    

年代:1996

数据来源: ASPB

ISSN:0032-0889    

DOI:10.1104/pp.110.1.15

出版商:American Society of Plant Biologists    

年代:1996

数据来源: ASPB

摘要:

For the nuclear replicating bipartite geminiviruses such as squash leaf curl to systemically infect the host requires the active participation of two virus-encoded movement proteins, BR1 and BL1. These act in a cooperative manner to transport the viral single-stranded DNA genome from its site of replication in the nucleus to the cell periphery (A.A. Sanderfoot, S.G. Lazarowitz [1995] Plant Cell 7: 1185–1194). We have proposed that BR1 functions as a nuclear shuttle protein, transporting the viral single-stranded DNA to and from the nucleus as a complex that is recognized by BL1 for movement to adjacent cells. To further investigate this, we expressed BR1 mutants known to affect viral infectivity in Spodoptera frugiperda insect cells and Nicotiana tabacum L. cv Xanthi protoplasts and found these to be defective in either their nuclear targeting or their ability to be redirected to the cell periphery when co-expressed with BL1. Translational fusions to [beta]-glucuronidase and alanine-scanning mutagenesis further demonstrated that the C-terminal 86 amino acids of BR1 contains a domain(s) essential for its interaction with BL1 and identified two nuclear localization signals within the N-terminal 113 residues of BR1. These nuclear localization signals were precisely located within distinct 16- and 22-peptide segments of BR1. These studies support and extend our model for squash leaf curl virus movement, showing that BR1 has a domain structure, with an N-terminal region required for nuclear targeting and a C-terminal region required for its interaction with BL

ISSN:0032-0889    

DOI:10.1104/pp.110.1.23

出版商:American Society of Plant Biologists    

年代:1996

数据来源: ASPB

摘要:

A cDNA clone corresponding to the gene (ZHA1) for a putative plasma membrane H+-ATPase of a seagrass (Zostera marina L.) was isolated and sequenced. Comparison of the amino acid predicted sequence from the nucleotide sequence of ZHA1 with those encoded by known genes for plasma membrane H+-ATPases from other plants indicated that ZHA1 is most similar to the gene (PMA4) for a plasma membrane H+-ATPase in a tobacco (84.4%). Northern hybridization indicated that ZHA1 was strongly expressed in mature leaves, which are exposed to seawater and have the ability of tolerate salinity; ZHA1 was weakly expressed in immature leaves, which are protected from seawater by tightly enveloping sheaths and are sensitive to salinity. In mature leaves, in situ hybridization revealed that ZHA1 was expressed specifically in epidermal cells, the plasma membranes of which were highly invaginated and morphologically similar to those of typical transfer cells. Therefore, the differentiation cell-like structures, accompanied by the high-level expression of ZHA1, in the epidermal cells of mature leaves in particular may be important for the excretion of salt by these cells.

ISSN:0032-0889    

DOI:10.1104/pp.110.1.35

出版商:American Society of Plant Biologists    

年代:1996

数据来源: ASPB

摘要:

An aromatic amino acid decarboxylase DNA fragment was generated from opium poppy (Papaver somniferum L.) genomic DNA by the PCR using primers designed from conserved amino acid sequences of other aromatic amino acid decarboxylase genes. Using this fragment as a probe, a genomic clone was isolated that encodes a new member of the opium poppy tyrosine/3,4-dihydroxyphenylalanine decarboxylase gene family (TyDC5). The predicted TyDC5 amino acid sequence shares extensive identity with other opium poppy tyrosine/3,4-dihydroxyphenylalanine decarboxylases (84%), and when expressed in Escherichia coli, it is active against tyrosine and to a lesser extent against 3,4-dihydroxyphenylalanine. Ribonuclease protection assays indicate that TyDC5 is expressed primarily in the roots of mature poppy plants. A peak of TyDC5 expression was also observed during germination, coincident with the emergence of the radicle from the seed coat. Parallel results were obtained in transgenic tobacco using a TyDC5 promoter fragment (-2060) translationally fused to the [beta]-glucuronidase reporter gene (GUS). In TyDC5::GUS tobacco, GUS activity transiently appeared in all parts of the seedling during germination, but was limited to the roots in older plants. These results indicate that TyDC5 expression is transcriptionally regulated and suggest that the TyDC5 enzyme may play an important role in providing precursors for alkaloid synthesis in the roots and germinating seedlings of opium poppy.

ISSN:0032-0889    

DOI:10.1104/pp.110.1.43

出版商:American Society of Plant Biologists    

年代:1996

数据来源: ASPB

摘要:

The first step of tryptophan biosynthesis is catalyzed by anthranilate synthase (AS), which is normally subject to feedback inhibition by tryptophan. Three independent trp5 mutants defective in the Arabidopsis thaliana AS [alpha] subunit structural gene ASA1 were identified by selection for resistance to the herbicidal compound 6-methylanthranilate. In all three mutants these biochemical changes are caused by a single amino acid substitution from aspartate to asparagine at residue position 341. Compared with the enzyme from wild-type plants, the tryptophan concentration causing 50% inhibition of AS activity in the trp5 mutant increased nearly 3-fold, the apparent Km for chorismate decreased by approximately 50%, and the apparent Vmax increased 60%. As a consequence of altered AS kinetic properties, the trp5 mutants accumulated 3-fold higher soluble tryptophan than wild-type plants. However, even though the soluble tryptophan levels were increased in trp5 plants, the concentrations of five tryptophan biosynthetic proteins remained unchanged. These data are consistent with the hypothesis that the reaction catalyzed by A. thaliana AS is rate limiting for the tryptophan pathway and that accumulation of tryptophan biosynthetic enzymes is not repressed by a 3-fold excess of end product.

ISSN:0032-0889    

DOI:10.1104/pp.110.1.51

出版商:American Society of Plant Biologists    

年代:1996

数据来源: ASPB

摘要:

Winter wheat (Triticum aestivum L. cv Monopol), spring wheat (Triticum aestivum L. cv Katepwa), and winter rye (Secale cereale L. cv Musketeer) grown at 5[deg]C and moderate irradiance (250 [mu]mol m-2 s-1) (5/250) exhibit an increased tolerance to photoinhibition at low temperature in comparison to plants grown at 20[deg]C and 250 [mu]mol m-2 s-1 (20/250). However, 5/250 plants exhibited a higher photosystem II (PSII) excitation pressure (0.32–0.63) than 20/250 plants (0.18–0.21), measured as 1 - qP, the coefficient of photochemical quenching. Plants grown at 20[deg]C and a high irradiance (800 [mu]mol m-2 s-1) (20/800) also exhibited a high PSII excitation pressure (0.32–0.48). Similarly, plants grown at 20/800 exhibited a comparable tolerance to photoinhibition relative to plants grown at 5/250. In contrast to a recent report for Chlorella vulgaris (D.P. Maxwell, S. Falk, N.P.A. Huner [1995] Plant Physiol 107: 687–694), this tolerance to photoinhibition occurs in winter rye with minimal adjustment to polypeptides of the PSII light-harvesting complex, chlorophyll a/b ratios, or xanthophyll cycle carotenoids. However, Monopol winter wheat exhibited a 2.5-fold stimulation of sucrosephosphate synthase activity upon growth at 5/250, in comparison to Katepwa spring wheat. We demonstrate that low-temperature-induced tolerance to photoinhibition is not a low-temperature-growth effect per se but, instead, reflects increased photosynthetic capacity in response to elevated PSII excitation pressure, which may be modulated by either temperature or irr

ISSN:0032-0889    

DOI:10.1104/pp.110.1.61

出版商:American Society of Plant Biologists    

年代:1996

数据来源: ASPB

摘要:

The recently described rhamnogalacturonase B, which is able to degrade ramified hairy regions of pectin, was found to be a rhamnogalacturonan [alpha]-L-rhamnopyranosyl-(1->4)-[alpha]-D-galactopyranosyluronide lyase. The cleavage site and mechanism differ from that of the previously described rhamnogalacturonase A, which is a hydrolase and can now be termed rhamnogalacturonan [alpha]-D-galactopyranosyluronide-(1->2)-[alpha]-L-rhamnopyranosyl hydrolase.

ISSN:0032-0889    

DOI:10.1104/pp.110.1.73

出版商:American Society of Plant Biologists    

年代:1996

数据来源: ASPB

摘要:

We have investigated the cis-acting potential of several as elements (20-bp as-1/ocs-like sequences) in both yeast and plant cells. These TGACG[N7]TGACG-resembling elements were surprisingly similar with respect to their ability to confer inducibility by auxins and related compounds to a heterologous TATA box in stably transformed plant cells. Both in plant cells and in yeast it was found that differences between as elements were of a quantitative nature. A strong element based on the consensus sequence for as elements conferred the highest level of gene expression. The rather aberrant as elements present in the promoters of auxin-inducible gst genes Nt103 and Nt114 of tobacco were much weaker cis-acting elements. The ability of an element to drive reporter gene expression was found to correlate with the extent to which proteins present in (nuclear) extracts of yeast and plant cells bound to it. The cloned transcription factor TGA1a was shown to be a very good candidate to be the factor that mediates the in vivo regulation of gene expression via as elements. The physiological significance of gene activation by active and inactive auxins is discussed.

ISSN:0032-0889    

DOI:10.1104/pp.110.1.79

出版商:American Society of Plant Biologists    

年代:1996

数据来源: ASPB