Occurrence of proteolytic inhibitors in various tissues of barley

Wound-Induced Proteinase Inhibitor in Plant Leaves: A Possible Defense Mechanism against Insects

Wounding of the leaves of potato or tomato plants by adult Colorado potato beetles, or their larvae, induces a rapid accumulation of a proteinase inhibitor throughout the plants' tissues that are exposed to air. This effect of insect damage can be simulated by mechanically wounding the leaves. The transport of a factor out of damaged leaves takes place rapidly after the wound is inflicted and the levels of proteinase inhibitor, in both damaged and adjacent leaves, rises strikingly within a few hours. The rapid accumulation of a powerful inhibitor of major intestinal proteinases of animals in response to wounding of the leaves is probably a defense mechanism.

Trypsin/alpha-amylase inhibitors inactivate the endogenous barley/malt serine endoproteinase SEP-1

Barley (Hordeum vulgare L.) malt contains endoproteinases belonging to all four of the commonly occurring classes, including serine proteinases. It also contains low molecular weight proteins that inhibit the activities of many of these endoproteinases, but it had never been shown that any barley or malt serine proteinases could be inhibited by any of these endogenous proteins. It is now reported that some proteins that were concentrated using an "affinity" method inhibited the activity of a malt serine endoproteinase. Two-dimensional electrophoretic and in vitro analyses showed that the inhibited enzyme was serine endoproteinase 1 (SEP-1) and that the inhibition could be quantified using a semipurified preparation of this enzyme. Amino acid sequencing and MALDI-TOF MS were used to identify the components of the partially purified inhibiting fractions. Only the "trypsin/alpha-amylase inhibitors" or chloroform/methanol (CM) proteins, most of which had truncated N and C termini, and one fragment of beta-amylase were present in the inhibitory fractions. When a CM protein fraction was prepared from barley according to traditional methods, some of its component proteins inhibited the activity of SEP-1 and some did not. This is the first report of the purification and identification of barley malt proteins that can inhibit an endogenous serine proteinase. It shows that some of the CM proteins probably play a role in controlling the activity of barley proteinases during germination, as well as possibly protecting the seed and young plant from microbes or pests.

Differential gene expression in the developing barley endosperm

Barley prolamin storage proteins account for 50% of the seed proteins. They are encoded by small multigene families that are only expressed in the developing endosperm. Previous work has shown that the major prolamins in barley are characterized by the presence of two or more unrelated structural domains, one of which contains repeated sequences. The non-repetitive domain is homologous with sequences present in other seed proteins found in the seed of mono- and dicotyledonous plants. Comparison of the 5' flanking region of a B1 hordein storage protein gene of barley with those of other prolamin genes (zeins and α-gliadins) reveals short sequences within 600 base pairs (bp) of the translation initiation codon that are strongly conserved. A short sequence at —300 bp seems to be unique to the prolamin genes and is possibly involved in the control of gene expression in the developing cereal endosperm. Six DNA-binding proteins have been identified that might recognize and interact with the putative regulatory sequences identified in the B1 hordein gene. Protease inhibitors account for a large proportion of the salt-soluble proteins of the barley seed, and contain up to 10% lysine. Cloned cDNAs for chymotrypsin inhibitors 1 and 2 have been isolated and characterized. All contain ochre stop condons in the sequences encoding a putative signal peptide. The two inhibitors are encoded by small multigene families that specify several subfamilies of mRNAs. The accumulation of chymotrypsin inhibitors in normal and mutant endosperms of barley is related to the abundances of their mRNAs.

A poplar tree proteinase inhibitor-like gene promoter is responsive to wounding in transgenic tobacco

Wounding of poplar trees leads to the accumulation of several mRNA species that encode proteins with putative defensive function. One class of wound-induced poplar RNA (win3) has amino acid sequence similarity to Kunitz-type trypsin inhibitors. Northern blots and cDNA sequencing show that several win3 mRNAs accumulate in the uninjured leaves of wounded trees. We report further characterization of the win3 family including sequence comparisons, gene family organization, and the identification of one win3 member that is transcriptionally activated in response to mechanical wounding. We also show that 1.5 kb of 5'-flanking sequence of one win3 member (win3.12) is sufficient to confer wound-regulated expression of a beta-D-glucuronidase (GUS) reporter gene in transgenic tobacco. Annual herbaceous plants such as tobacco can thus be used to study the expression of genes from a perennial woody angiosperm.

Influence of formic acid on fungal flora of barley and on aflatoxin production in Aspergillus flavus link

In recent years Aspergillus flavus and aflatoxin production have been noted on several occasions in grain preserved with formic acid. Samples of mouldy barley treated with formic acid and stored in an open bin were investigated for the presence of fungi. In the lower part of the bin there was a clear dominance of Fusarium sporotrichioides, and deoxynivalenol and neosolaniol were detected. A. flavus and A. fumigatus were also present. Paecilomyces variotii occurred, almost as a pure culture, in the upper part of the bin, but no patulin was found. Cultivation of four fungal isolates from these genera on laboratory substrates containing formic acid showed P. variotii to be the most tolerant to formic acid, withstanding 150 mM, but still without patulin production. F. sporotrichioides and A. fumigatus tolerated only 6 mM formic acid. The growth of A. flavus was reduced and atypical at 60 mM formic acid. Pretreatment of A. flavus spores with formic acid increased aflatoxin production about 800 times.

Isolation of the first trypsin inhibitor from the genus Aspergillus

The fungus Aspergillus flavipes was grown on a Czapeck sucrose medium; the biomass so obtained was treated with high concentration of sucrose to release intracellular metabolites. Sephadex G-75 chromatography of the latter yielded a pure protein having anti-trypsin activity in vitro.

Characterization of active dipeptide transport by germinating barley embryos: Effects of pH and metabolic inhibitors

A sensitive new fluorescent method is outlined for the study of peptide and amino acid transport processes. Studies on dipeptide transport in germinating barley (Hordeum vulgare.) embryos have provided evidence for accumulation of substrate against a concentration gradient, saturation kinetics, a pH optimum at pH 3.8, and inhibition by a variety of metabolic inhibitors. Acetate also inhibits transport, possibly by disrupting H(+) gradients across the plasma membrane.

Metabolism of trypsin-inhibitory proteins in the germinating seeds of kidney bean (Phaseolus vulgaris)

A number of proteins with trypsin-inhibitory activity was separated by isoelectric focusing and their amounts measured in the extracts of the seeds of kidney bean at various stages of germination up to 16 days.The total trypsin inhibitor content of the dormant seed, 2.2 mg per g bean rose to about 3.6 mg by the seventh day and declined slowly after the tenth day of germination. The individual trypsin inhibitors however, appeared to change independently of each other and some components disappeared almost completely with the progress of germination. The emergence of an inhibitor not found in the dormant seed was also observed. Some of the inhibitor proteins attained a maximum concentration by the 7-8th day of germination. This coincided with a similar maximum in the general protein and proteolytic enzyme content of the germinating bean seeds. The results obtained suggested that the main function during germination of these protein components might not be related to their trypsin-inhibitory activity.