Fusariotoxicosis from barley in British Columbia. I. Natural occurrence and diagnosis.
(1/2002)
Clinical sickness was observed in domestic ducks, geese, horses and swine during October 1973. All species showed upper alimentary distress with mortalities occurring in the geese. Barley derived from a common source had been fed. Examination of the barley revealed invasion by Fusarium spp and detection of a high level of dermatitic fusariotoxins. (+info)
Fusariotoxicosis from barley in British Columbia. II. Analysis and toxicity of syspected barley.
(2/2002)
Fusariotoxin T-2, a trichothecene, was tentatively identified in barley samples which caused field outbreaks of mycotoxicosis in British Columbia. Geese died when fed the contaminated barley experimentally but mice were little affected after long term feeding. The methods used in the laboratory for trichothecene extraction and identification of T-2 toxin are described. (+info)
A single limit dextrinase gene is expressed both in the developing endosperm and in germinated grains of barley.
(3/2002)
The single gene encoding limit dextrinase (pullulan 6-glucanohydrolase; EC 3.2.1.41) in barley (Hordeum vulgare) has 26 introns that range in size from 93 to 822 base pairs. The mature polypeptide encoded by the gene has 884 amino acid residues and a calculated molecular mass of 97,417 D. Limit dextrinase mRNA is abundant in gibberellic acid-treated aleurone layers and in germinated grain. Gibberellic acid response elements were found in the promoter region of the gene. These observations suggest that the enzyme participates in starch hydrolysis during endosperm mobilization in germinated grain. The mRNA encoding the enzyme is present at lower levels in the developing endosperm of immature grain, a location consistent with a role for limit dextrinase in starch synthesis. Enzyme activity was also detected in developing grain. The limit dextrinase has a presequence typical of transit peptides that target nascent polypeptides to amyloplasts, but this would not be expected to direct secretion of the mature enzyme from aleurone cells in germinated grain. It remains to be discovered how the enzyme is released from the aleurone and whether another enzyme, possibly of the isoamylase group, might be equally important for starch hydrolysis in germinated grain. (+info)
Primary and secondary structural elements required for synthesis of barley yellow dwarf virus subgenomic RNA1.
(4/2002)
Barley yellow dwarf luteovirus (BYDV) generates three 3'-coterminal subgenomic RNAs (sgRNAs) in infected cells. The promoter of sgRNA1 is a putative hot spot for RNA recombination in luteovirus evolution. The sgRNA1 transcription start site was mapped previously to either nucleotide 2670 or nucleotide 2769 of BYDV genomic RNA (gRNA) in two independent studies. Our data support the former initiation site. The boundaries of the sgRNA1 promoter map between nucleotides 2595 and 2692 on genomic RNA. Computer prediction, phylogenetic comparison, and structural probing revealed two stem-loops (SL1 and SL2) in the sgRNA1 promoter region on the negative strand. Promoter function was analyzed by inoculating protoplasts with a full-length infectious clone of the BYDV genome containing mutations in the sgRNA promoter. Because the promoter is located in an essential coding region of the replicase gene, we duplicated it in a nonessential part of the genome from which a new sgRNA was expressed. Mutational analysis revealed that secondary structure, but not the nucleotide sequence, was important at the base of SL1. Regions with both RNA primary and secondary structural features that contributed to transcription initiation were found at the top of SL1. Primary sequence, but not the secondary structure, was required in SL2, which includes the initiation site. Disruption of base pairing near the sgRNA1 start site increased the level of transcription three- to fourfold. We propose that both primary and secondary structures of the sgRNA1 promoter of BYDV play unique roles in sgRNA1 promoter recognition and transcription initiation. (+info)
Barley BLZ2, a seed-specific bZIP protein that interacts with BLZ1 in vivo and activates transcription from the GCN4-like motif of B-hordein promoters in barley endosperm.
(5/2002)
A barley endosperm cDNA, encoding a DNA-binding protein of the bZIP class of transcription factors, BLZ2, has been characterized. The Blz2 mRNA expression is restricted to the endosperm, where it precedes that of the hordein genes. BLZ2, expressed in bacteria, binds specifically to the GCN4-like motif (GLM; 5'-GTGAGTCAT-3') in a 43-base pair oligonucleotide derived from the promoter region of a Hor-2 gene (B1-hordein). This oligonucleotide also includes the prolamin box (PB; 5'-TGTAAAG-3'). Binding by BLZ2 is prevented when the GLM is mutated to 5'-GTGctTCtc-3' but not when mutations affect the PB. The BLZ2 protein is a potent transcriptional activator in a yeast two-hybrid system where it dimerizes with BLZ1, a barley bZIP protein encoded by the ubiquitously expressed Blz1 gene. Transient expression experiments in co-bombarded developing barley endosperms demonstrate that BLZ2 transactivates transcription from the GLM of the Hor-2 gene promoter and that this activation is also partially dependent on the presence of an intact PB. A drastic decrease in GUS activity is observed in co-bombarded barley endosperms when using as effectors equimolar mixtures of Blz2 and Blz1 in antisense constructs. These results strongly implicate the endosperm-specific BLZ2 protein from barley, either as a homodimer or as a heterodimer with BLZ1, as an important transcriptional activator of seed storage protein genes containing the GLM in their promoters. (+info)
Protochlorophyllide b does not occur in barley etioplasts.
(6/2002)
Barley (Hordeum vulgare L.) etioplasts were isolated, and the pigments were extracted with acetone. The extract was analyzed by HPLC. Only protochlorophyllide a and no protochlorophyllide b was detected (limit of detection < 1% of protochlorophyllide a). Protochlorophyllide b was synthesized starting from chlorophyll b and incubated with etioplast membranes and NADPH. In the light, photoconversion to chlorophyllide b was observed, apparently catalyzed by NADPH :protochlorophyllide oxidoreductase. In darkness, reduction of the analogue zinc protopheophorbide b to zinc 7-hydroxy-protopheophorbide a was observed, apparently catalyzed by chlorophyll b reductase. We conclude that protochlorophyllide b does not occur in detectable amounts in etioplasts, and even traces of it as the free pigment are metabolically unstable. Thus the direct experimental evidence contradicts the idea by Reinbothe et al. (Nature 397 (1999) 80-84) of a protochlorophyllide b-containing light-harvesting complex in barley etioplasts. (+info)
Formation of lipoxygenase-pathway-derived aldehydes in barley leaves upon methyl jasmonate treatment.
(7/2002)
In barley leaves, the application of jasmonates leads to dramatic alterations of gene expression. Among the up-regulated gene products lipoxygenases occur abundantly. Here, at least four of them were identified as 13-lipoxygenases exhibiting acidic pH optima between pH 5.0 and 6.5. (13S,9Z,11E,15Z)-13-hydroxy-9,11,15-octadecatrienoic acid was found to be the main endogenous lipoxygenase-derived polyenoic fatty acid derivative indicating 13-lipoxygenase activity in vivo. Moreover, upon methyl jasmonate treatment > 78% of the fatty acid hydroperoxides are metabolized by hydroperoxide lyase activity resulting in the endogenous occurrence of volatile aldehydes. (2E)-4-Hydroxy-2-hexenal, hexanal and (3Z)- plus (2E)-hexenal were identified as 2,4-dinitro-phenylhydrazones using HPLC and identification was confirmed by GC/MS analysis. This is the first proof that (2E)-4-hydroxy-2-hexenal is formed in plants under physiological conditions. Quantification of (2E)-4-hydroxy-2-hexenal, hexanal and hexenals upon methyl jasmonate treatment of barley leaf segments revealed that hexenals were the major aldehydes peaking at 24 h after methyl jasmonate treatment. Their endogenous content increased from 1.6 nmol.g-1 fresh weight to 45 nmol.g-1 fresh weight in methyl-jasmonate-treated leaf segments, whereas (2E)-4-hydroxy-2-hexenal, peaking at 48 h of methyl jasmonate treatment increased from 9 to 15 nmol.g-1 fresh weight. Similar to the hexenals, hexanal reached its maximal amount 24 h after methyl jasmonate treatment, but increased from 0.6 to 3.0 nmol.g-1 fresh weight. In addition to the classical leaf aldehydes, (2E)-4-hydroxy-2-hexenal was detected, thereby raising the question of whether it functions in the degradation of chloroplast membrane constituents, which takes place after methyl jasmonate treatment. (+info)
Effect of the glycemic index and content of indigestible carbohydrates of cereal-based breakfast meals on glucose tolerance at lunch in healthy subjects.
(8/2002)
BACKGROUND: Diets with a low glycemic index (GI) have been shown to improve glucose tolerance in both healthy and diabetic subjects. Two potential mechanisms are discussed in relation to long-term metabolic effects: a decreased demand for insulin in the postprandial phase and formation of short-chain fatty acids from fermentation of indigestible carbohydrates in the colon. OBJECTIVE: The objective was to study the effect of the GI and the indigestible carbohydrate--resistant starch (RS) and dietary fiber (DF)--content of cereal-based breakfasts on glucose tolerance at a second meal (lunch) in healthy subjects. DESIGN: The effects of 7 test breakfasts with known GIs (GI: 52-99) and RS + DF contents (2-36 g) were evaluated. White-wheat bread was used as a reference breakfast (high GI, low RS + DF content). Glucose and insulin responses after the second meal were measured in healthy subjects. In addition, the satiating capacity of 4 of the 7 test breakfasts was estimated before and during the second meal. RESULTS: Two of the 4 low-GI breakfasts improved glucose tolerance at the second meal. Only these 2 breakfasts were capable of postponing the in-between-meal fasting state. There was no measurable effect of fermentable carbohydrates on glucose tolerance at the second meal. The highest satiety score was associated with the barley breakfast that had a low GI and a high RS + DF content. CONCLUSIONS: Glucose tolerance can improve in a single day. Slow absorption and digestion of starch from the breakfast meal, but not the content of indigestible carbohydrates in the breakfast meal, improved glucose tolerance at the second meal (lunch). (+info)