The synthesis of hemolymph proteins by the larval midgut of an insect Calpodes ethlius (Lepidoptera:Hesperiidae)

Ligated tubes of Calpodes ethlius (Lepidoptera:Hesperiidae) larval midgut with normal (i.e. apical secretions into the lumen and basal into the hemocel or medium) or inverted orientation (i.e. apical secretions into the hemocoel or medium and basal into the lumen) were incubated in artificial hemolymph in the presence of [³⁵S]methionine to investigate protein synthesis and vectorial secretion. The midgut synthesizes and secretes at least eight polypeptides basally and seven apically. The tissue also synthesizes many other polypeptides that are not released at either surface. Two dimensional analysis of proteins labeled in vitro and in vivo showed that (a) proteins synthesized in vitro are the same as those synthesized in vivo, (b) different proteins are secreted on apical and basal surfaces, (c) in vitro apical secretions are the same as in vivo luminal proteins, (d) at least two of the basal secretions can be demonstrated in the hemolymph labeled in vivo. Almost all basal secretions showed immunological similarity with hemolymph proteins as observed by immunoprecipitation and fluorography. Arylphorin is a main hemolymph protein synthesized by the midgut. Midgut arylphorin has been identified by its precipitation by antibodies to hemolymph arylphorin. We conclude that insect midgut has bi-directional secretion. Luminal proteins (presumably digestive enzymes and perhaps goblet cell luminal contents) are carried to the apical face. A different set of proteins are carried basally to the hemolymph.     

A function for pericardial cells in an insect

The pericardial cells (PCs) of fifth instar Calpodes ethlius larvae are functionally adapted for filtering hemolymph and sequestering and digesting proteins. They also have a structure appropriate for the synthesis of proteins for secretion. PC secretion has been investigated by labelling the cells with [³⁵S]methionine ti vitro with detection of newly synthesized polypeptides appearing in the medium by electrophoresis and fluorography. Sources possibly contributing to the appearance of newly synthesized polypeptides in the medium, such as cell breakdown and fat body contamination have been ruled out. The post-incubation medium of PCs contains at least six newly synthesized polypeptides. Three of these polypeptides, having relative molecular masses of 82, 57 and 43 kDa, react with antibodies to hemolymph. At least one additional polypeptide is similar by two-dimensional analysis to that naturally present in hemolymph. PCs incubated together with the heart to which they are normally attached, secrete additional polypeptides that are presumed to come from the heart. The 82 kDa polypeptide secreted by the PCs is similar to the subunits of arylphorin secreted by fat body and other tissues. We conclude that PCs secrete proteins into the hemolymph although the amount may be small relative to that of the fat body.     

Integument and hemocyte peptides

There are four routing classes of integument peptide in the caterpillar of Calpodes ethlius. The epidermis secretes peptides apically into the cuticle (C), basally into the hemolymph (H) and in both directions (BD). Peptides in a 4th class (T), are presumed to be transported across the epidermis, because the epidermis does not synthesize them although they occur in both cuticle and hemolymph. In a search for the origin of the presumed transepidermal peptides we found that hemocytes contain some peptides from all four routing classes. Peptides prepared from washed hemocytes reacted in immunoblots to antibodies against integument peptides prepared from hemolymph and cuticle. These peptides are probably synthesized by hemocytes because they matched those from medium containing [³⁵S]methionine in which hemocytes had been incubated. Calpodes hemolymph contains four hemocyte types. Immunogold labelling localized integument peptides in the secretory pathway of granulocytes and spherulocytes and in the cytosol of oenocytoids but not in plasmatocytes. Each peptide was localized in a particular kind or kinds of hemocyte. Granulocyte secretory vesicles reacted with antibodies to C180, C55 and BD82 kDa peptides. Spherulocytes secretory vesicles reacted with antibodies to C180, C55, BD89, BD82 and a 78 kDa peptide presumed to be the precursor of T66. Oenocyotoids reacted with antibodies to H45, 38, 32, 23 and BD89 kDa peptides. Spherulocytes were the only tissue to react with antibodies to the T66 kDa peptide that is found abundantly in cuticle and hemolymph. Spherulocytes are therefore presumed to secrete the 66 kDa peptide into the hemolymph from where it is transported to the cuticle. The C180 and C55 kDa peptides do not occur in hemolymph. Their presence in granulocytes and spherulocytes may be associated with hemocyte functions such as basal lamina formation, since immunogold localized them in that part of the basal lamina next to the hemolymph, as would be expected if hemocytes deposited components onto the exposed hemolymph surface. The presence of hemolymph peptides in oenocytoids is more difficult to interpret, since the antigenic reactions are localized in the cytosol rather than in the secretory pathway expected for exported proteins. We conclude that integument peptides are not secreted only by the epidermis, nor is the cuticle their only destination.     

Disruption of microfilaments alters laminin synthesis but not laminin trafficking in NHEKin vitro

Summary Laminin synthesis and deposition are concomitant with the development of a basal lamina between the human epidermis and the underlying dermis. One of the challenges in tissue engineering of human epidermal models is to develop substrates and conditions that encourage the development of a basement membrane. The purpose of this study was to determine if actin filaments and/or microtubules are involved in the synthesis/secretion of laminin by normal human epidermal keratinocytes (NHEK)in vitro. NHEK synthesize and secrete laminin subunits B1, B2, and M but little, if any, of laminin subunit A. Data indicate that disruption of microfilaments by the destabilizing agent, cytochalasin D, had no apparent effect on the relative synthesis rates of most cytosolic proteins as, revealed by one-dimensional sodium dodecyl sulfate (SDS) gel electrophoresis. This drug, however, increased laminin B2 synthesis several fold over untreated controls. This enhanced synthetic rate was independent of the type of collagen, matrix on which the NHEK were grown. Similar increases in synthesis of the M and B1 laminin chains were not observed. To determine if this increase in synthesis lead to increases in laminin B2 secretion, laminin B2 was immunoprecipitated from both the apical and basal domains of NHEK cells grown on microporous membranes. While more laminin B1, B2, and M were secreted basally than apically, an observation consistent with laminin’s role in basal lamina formation, cytochalasin D had no apparent effect on either basal or apical laminin B2 secretion. Experiments with the microtubule destabilizer, nocodazole, showed no similar effects on laminin synthesis and/or secretion. We conclude that (a) disruption of the actin network in NHEK selectively increases the synthesis of laminin B2, (b) the secretion of laminin B2 from NHEK cells is not governed by either the microfilamentous cytoskeleton or the amount of laminin synthesized by NHEK, and (c) disruption of the microtubular network does not alter laminin synthesis or secretion.     

The Regulation of yolk polypeptide synthesis in Drosophila ovaries and fat body by 20-hydroxyecdysone and a juvenile hormone analog

In adult female Drosophila melanogaster an increase in the synthesis and secretion of three yolk polypeptides (YPs) occurs during the first 24 hr after eclosion. During organ culture, these same polypeptides are synthesized and secreted into the medium by both fat body and ovaries. Two hormones, 20-hydroxyecdysone (20-HE) and a juvenile hormone analog (ZR-515) stimulate synthesis and secretion of YPs into the hemolymph of isolated female abdomens. The present experiments were undertaken to compare synthesis of YPs in normal females with YP synthesis in preparations deprived of anterior endocrine glands, and to find which hormone stimulates synthesis in the different organs. Separation of hemolymph proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that at eclosion incorporation of [³⁵S]methionine into YP1 and YP2 was low and was barely detectable in YP3. Over the next 24 hr the rate of label incorporation increased for all the YPs. Isolation of female abdomens at eclosion prevented this increase in label incorporation but did not entirely abolish YP synthesis. Application of either ZR-515 or 20-HE to isolated abdomens stimulated up to ninefold label incorporation into three polypeptides which comigrated with YPs from normal vitellogenic females. The response of isolated abdomens to ZR-515 or 20-HE was first detectable between 90 and 135 min after hormone application. The stimulated bands were confirmed to be YPs by a comparison of peptide digests of each of the three labeled polypeptides with those of the yolk polypeptides from intact vitellogenic females. The hypothesis that the two hormones might act on different organs was tested by treating isolated female abdomens with various concentrations of either ZR-515 or 20-HE and then culturing the stimulated organ in vitro with [³⁵S]methionine. The fat body responded to both hormones by synthesizing and secreting into the culture medium polypeptides which comigrated with the YPs found in hemolymph, whereas the ovary produced similar polypeptides only after ZR-515. These secreted polypeptides were confirmed to be YPs by repeating the experiment using organs from heterozygotes for both YP2 and YP3 electrophoretic variants. Such organs synthesized five polypeptides which comigrated with the corresponding yolk polypeptides. These findings are discussed in relation to a hypothesis for the action of the two hormones.     

Lipopolysaccharide-binding protein is vectorially secreted and transported by cultured intestinal epithelial cells and is present in the intestinal mucus of mice

Lipopolysaccharide-binding protein (LBP) is an important modulator of the host's response to endotoxin. In a previous study, we found evidence for the synthesis of LBP by intestinal epithelial cells. In this study, we explored the polarity of LBP secretion by these cells. Polarized monolayers of Caco-2 cells were used as intestinal mucosa model. Cells were stimulated apically or basally with cytokines, and LBP secretion was analyzed. Furthermore, the presence of LBP in intestinal mucus of healthy and endotoxemic mice was studied using a mucus-sampling technique. The constitutive unipolar LBP secretion from the apical cell surface was markedly enhanced when cells were exposed to cytokines at their apical surface. However, bioactive LBP was secreted from both cell surfaces after basolateral stimulation of cells. Cytokines also influenced the secretion of the acute phase proteins serum amyloid A, apoA-I, and apoB from both surfaces of Caco-2 cells. Furthermore, transport of exogenous LBP from the basolateral to the apical cell surface was demonstrated. In line with these in vitro data, the presence of LBP in intestinal mucus was strongly enhanced in mice after a challenge with endotoxin. The results indicate that LBP is present at the mucosal surface of the intestine, a phenomenon for which secretion and transport of LBP by intestinal epithelial cells may be responsible.     

Vectorial secretion of extracellular matrix proteins, matrix-degrading proteinases, and tissue inhibitor of metalloproteinases by endothelial cells

In a study of the vectorial secretion of proteins by bovine aortic arch endothelial cells, we found that the extracellular matrix macromolecules collagen and fibronectin as well as several matrix-degrading metalloproteinases were secreted selectively in the basal direction. In contrast, the tissue inhibitor of metalloproteinases showed only a weak preference for the basal direction. Three proteins at 18-35 kDa were secreted with preference apically, counter to the basal secretion of approximately 70% of the total secreted protein. As expected, rabbit synovial fibroblasts, which were used as a control, secreted proteins, including collagen, gelatin-degrading proteinases, and casein-degrading proteinases, equally in apical and basal directions. The basal secretion of collagen, fibronectin, gelatinases, and tissue inhibitor of metalloproteinases by bovine aortic arch endothelial cells suggests that the structural and functional polarity of these cells is manifested, in part, at the level of polarized secretion of matrix-related proteins.     

Auxin reduces the synthesis of major vacuolar proteins in tobacco mesophyl protoplast

We have established that polypeptides whose synthesis is reduced by 2,4-dichlorophenoxyacetic acid during in vitro culture of tobacco mesophyll protoplasts are secreted into the vacuole where they constitute the bulk of labeled proteins. In addition, these proteins continue to be synthesized in protoplast-derived cultured cells and their synthesis is strictly correlated with the size of the cell, i.e. with vacuolar size.     

Comparison of Yolk Production in Seven Pyralid Moth Species

Summary

The yolk proteins of six pyralid moths were analyzed and compared with the yolk proteins of Plodia interpunctella (Hübner). When cross-reacted in an Ouchterlony double immunodiffusion with antiserum raised to either total yolk proteins or purified vitellin from P. tnterpunctella, the yolk proteins of Anagasta kuehniella (Zeller), Cadra cautella (Walker), C. figulilella (Gregson), and Ephestia elutella (Hübner), closely related members of the subfamily Phycitinae, showed strong precipitation lines that consisted of four major yolk polypeptides (YPs). The yolk proteins from Amyelois transitella (Walker) were only weakly reactive, whereas yolk proteins from Galleria mel-lonella (L.) were not precipitated by either antiserum. Abdominal body walls (containing primarily fat body) from late pharate adult females were incubated in vitro and they secreted two major polypeptides that had molecular masses similar to the vitellogenins (YP1 and YP3) from P. interpunctella. In addition, ovarioles from late pharate adult females were incubated in vitro, and they secreted two major polypeptides that had molecular masses similar to YP2 and YP4 from P. interpunctella. When late pharate adult females were injected with ³⁵S-Met, the hemolymph of all species contained vitellogins that were secreted by their respective body walls in vitro. Ovarioles from injected females contained many labeled polypeptides, but there were four major bands that corresponded consistently to the vitellogenins secreted from the fat body and the two major polypeptides secreted from the ovarioles. These data show that the production of the major YPs in these closely related pyralid species is very similar, and that there is considerable conservation of immunological characters of yolk proteins in the subfamily Phycitinae.     

Secreted proteins from rat Sertoli cells.

Sertoli cell cultures were prepared from the testes of 20-day-old rats. The proteins which were secreted by the cells into the culture medium were labeled with [³H]leucine or l-[³H]fucose. The proteins were concentrated by ultrafiltration and analysed by polyacrylamide slab gel electrophoresis (PAGE) in the presence of sodium dodecyl sulfate (SDS). Autofluorography of the gels at ?70 °C showed that the rat Sertoli cells synthesized and secreted at least 7 major polypeptides. The polypeptides had molecular weights ranging from 16 000 to 140 000 D. Proteins which were secreted from cultures of testicular fibroblasts and myoid cells had electrophoretic properties on SDS-PAGE which were different from Sertoli cell secreted proteins. Addition of FSH and testosterone to the Sertoli cell cultures increased the total synthesis and secretion of [³H]leucine-labeled proteins. No qualitative changes in the proteins as a result of hormone application could be detected. However, the synthesis of a polypeptide of molecular weight 48 000 was increased relative to the other secreted peptides if the cells were maintained in FSH and testosterone. The Sertoli cell secreted proteins were shown to be glycoproteins which can bind to ConA-Sepharose and can be labeled with [³H]fucose. Tunicamycin, a specific inhibitor of N-glycosylation, inhibited the secretion of [³H]proteins by 50% but had little effect on the intracellular protein synthesis.     

Polarized secretion of an ectopic protein in Drosophila salivary glands in vivo.

Epithelial cells can secrete specific proteins in a polarized manner, either from the apical or basolateral surface. Intracellular protein sorting which results in polarized secretion has previously been studied using epithelial tissue culture cells. We describe here the use of Drosophila larval salivary glands for the study of polarized secretion by epithelia in vivo, and address whether an ectopically synthesized secretory protein can be sorted and targeted to the correct cell surface for secretion. Larval cuticle proteins (LCPs) and salivary gland secretion (Sgs) proteins of Drosophila melanogaster are apically secreted proteins that are produced respectively by the epidermis and salivary glands. We have transformed Drosophila with a hybrid gene consisting of the sgs-4 promoter sequence and the coding sequence for a variant (LCP-f2) of LCP-2. We have found that transgenic late third instar larvae produce LCP-f2 only in the salivary glands and that LCP-f2 is properly secreted in vivo in a polarized manner from only the apical surface of the cells into the gland lumen. The results indicate that apical secretion does not depend on a tissue-specific targeting signal contained within the protein.     

Secretory cargo composition affects polarized secretion in MDCK epithelial cells

Polarized epithelial cells secrete proteins at either the apical or basolateral cell surface. A number of non-epithelial secretory proteins also exhibit polarized secretion when they are expressed in polarized epithelial cells but it is difficult to predict where foreign proteins will be secreted in epithelial cells. The question is of interest since secretory epithelia are considered as target tissues for gene therapy protocols that aim to express therapeutic secretory proteins. In the parathyroid gland, parathyroid hormone is processed by furin and co-stored with chromogranin A in secretory granules. To test the secretion of these proteins in epithelial cells, they were expressed in MDCK cells. Chromogranin A and a secreted form of furin were secreted apically while parathyroid hormone was secreted 60% basolaterally. However, in the presence of chromogranin A, the secretion of parathyroid hormone was 65% apical, suggesting that chromogranin can act as a “sorting escort” (sorting chaperone) for parathyroid hormone. Conversely, apically secreted furin did not affect the sorting of parathyroid hormone. The apical secretion of chromogranin A was dependent on cholesterol, suggesting that this protein uses an established cellular sorting mechanism for apical secretion. However, this sorting does not involve the N-terminal membrane-binding domain of chromogranin A. These results suggest that foreign secretory proteins can be used as “sorting escorts” to direct secretory proteins to the apical secretory pathway without altering the primary structure of the secreted protein. Such a system may be of use in the targeted expression of secretory proteins from epithelial cells. David V. Cohn—Deceased.     

Sexual phenotype and vitellogenin synthesis in Drosophila melanogaster

An ovary transplanted from a Drosophila melanogaster female into a male will mature and form morphologically normal yolk-filled oocytes. Since it has been supposed that the yolk polypeptides come only from the female fat body, it was hypothesized that the implanted ovary induces the fat body of the male host to synthesize and secrete yolk polypeptides (YPs). To test this hypothesis, fat body preparations from females, untreated males, and males containing transplanted ovaries were cultured in vitro with ³⁵S-methionine and the medium was examined for the presence of newly labeled YPs. Female fat body secreted newly labeled YPs, but no freshly synthesized YPs were secreted by fat bodies from untreated males or from males containing transplanted ovaries. In vitro cultured ovaries, however, both from females and from male hosts did secrete newly synthesized YPs. Therefore, the YPs in an ovary that matured in a male come mainly from endogenous synthesis by the implanted ovary. To find whether males were responsive to the hormones that stimulate YP production in isolated female abdomens, we treated males with the juvenile hormone analogue ZR-515 and with 20-hydroxyecdysone. The latter, but not the former, was able to cause synthesis and secretion of three bands migrating precisely as YPs in SDS gels. Partial peptide digests of the 20-hydroxyecdysone-stimulated polypeptides in males showed them to be identical with those stimulated by 20-hydroxyecdysone or ZR-515 in isolated female abdomens and with the three YPs found in normal female hemolymph. Finally, YP synthesis was assayed in mutants that affect the phenotypic sex of a fly. It was found that flies bearing two X chromosomes and the mutations dsx, dsx^D, ix or three sets of autosomes continued to make YPs, but tra-3-pseudomales did not. These results suggest that the process of sex determination involves steps leading to synthesis of an ecdysteroid in females, which then activates synthesis of the YPs by the fat body. A hypothesis is suggested to explain the fact that two different hormones can stimulate YP synthesis and two different organs can synthesize YPs.     

SOURCES OF LARVAL SALIVARY GLAND SECRETION IN THE DIPTERAN CHIRONOMUS TENTANS

The soluble proteins in the hemolymph, the salivary gland, and the salivary secretion of fourth instar Chironomus tentans were examined by disc electrophoresis in acrylamide gels. Of the 11 protein fractions detected in buffered saline extracts of the gland, 10 are present also in the hemolymph. Amino acid isotope incorporation experiments indicate that the protein fractions shared by the salivary gland and the hemolymph are not synthesized in the gland but are synthesized in other larval tissues. Immunochemical studies show that most of these proteins eventually are secreted from the gland. The salivary gland in vivo and in vitro is active in de novo protein synthesis. The protein synthesized tends to form large molecular weight aggregates. As demonstrated by radioautography, at least 80% of this protein is secreted from the 30 large cells forming most of the gland. The proteins synthesized in the salivary gland cannot be detected in the hemolymph. The results of this investigation are consistent with a mechanism of secretion formation involving both de novo synthesis of some secretion proteins and the selective uptake, transport, and secretion of hemal proteins by the salivary gland.     

PSOP1, putative secreted ookinete protein 1, is localized to the micronemes of Plasmodium yoelii and P. berghei ookinetes

Plasmodium parasites cause malaria in mammalian hosts and are transmitted by Anopheles mosquitoes. Activated gametocytes in the mosquito midgut egress from erythrocytes followed by fertilization and zygote formation. Zygotes differentiate into motile invasive ookinetes, which penetrate the midgut epithelium before forming oocysts beneath the basal lamina. Ookinete development and traversal across the mosquito midgut wall are major bottlenecks in the parasite life cycle. In ookinetes, surface proteins and proteins stored in apical organelles have been shown to be involved in parasite-host interactions. A group of ookinete proteins that are predicted to have such functions are named PSOPs (putative secreted ookinete protein). PSOP1 is possibly involved in migration through the midgut wall, and here its subcellular localization was examined in ookinetes by immunoelectron microscopy. PSOP1 localizes to the micronemes of Plasmodium yoelii and Plasmodium berghei ookinetes, indicating that it is stored and possibly apically secreted during ookinete penetration through the mosquito midgut wall.     

The transparent accessory reproductive gland secretes a polypeptide into the hemolymph of male Rhodnius prolixus

The transparent accessory reproductive gland of Rhodnius prolixus synthesizes and accumulates a variety of polypeptides. Ouchterlony immunodiffusion demonstrates that the hemolymph contains proteins which react with polyclonal antibodies against extracts of transparent accessory glands. Accessory glands and hemolymph contain a 170 kDa polypeptide with similar mobility on SDS-polyacrylamide gel electrophoresis. This polypeptide reacts with antibodies against extracts of accessory glands. Surgical removal of the accessory glands prevents the appearance of the 170 kDa polypeptide in the hemolymph. In vivo labeling of accessory gland proteins with a mixture of [¹⁴C]amino acids demonstrates that the newly synthesized TARG polypeptide appears in the hemolymph between days 2 and 3 after feeding. It is concluded that a specific polypeptide which is synthesized in the transparent accessory gland is exported to the hemolymph.     

Anatomical aspects of the gynoecium of species of Anthurium sect. Urospadix Engl. (Araceae,Alismatales)

Anthurium sect. Urospadix includes approximately 70 species differently distributed in Eastern Brazil, Western South America, and Central America. The present work studied the gynoecia of species of section Urospadix to describe their anatomical features. In all the species studied, the apical portion of the gynoecium differentiates into a stigma covered with short trichomes and an adjacent region formed by isodiametric cells. The stylar canal comprises short, unicellular secretory trichomes extending up to the ovarian aperture. Carpels are apically symplicate and basally synascidiate with a septum that does not reach the apical portion of the locule. The apical portion of the septum differentiates into long, secretory trichomes while the subapical one differentiates into the placenta. Locules are filled with mucilage. Since the epidermis of the region adjacent to the stigma, the length of the stylar portion, and the number of cell layers of the ovarian septum vary among the species studied, they may be useful for further taxonomic and systematic purposes. The present work is the first detailed report of trichome location and distribution on the gynoecia of Anthurium.     

Elektronenmikroskopische Untersuchungen anAnaitides mucosa (Annelida,Polychaeta). Cuticula und Cilien,Schleimzellen und Schleimextrusion

Two components, a basal cuticle and an epicuticle, make up the cuticle ofA. mucosa. The basal cuticle consists of collagen fibrils, which are arranged in about 20 layers. The orientation of the fibrils changes rectangularly from one layer to the next. Fine filaments interweave the basal cuticle. The epicuticle, which is covered by a layer of electron dense material, is composed of irregularly arranged thin filaments. Branched microvilli of the epidermal cells penetrate the cuticle. Bacteria are found in the basal cuticle. Dorsally each segment has a band of densely packed smooth cilia. Laterally and partly ventrally aggregates of cilia are observed. These cilia exhibit apically artificial swellings. At least six different mucous cells are observed in the epidermis, morphologically distinguishable by the structure of the secretion products. Mucus is secreted via exocytosis through cuticular pores. During this process the mucus might expand. The secreted mucus consists of filamentous subunits.     

A Comparison of the Effect of Salt on Polypeptides and Translatable mRNAs in Roots of a Salt-Tolerant and a Salt-Sensitive Cultivar of Barley

The effect of salt stress on polypeptide and mRNA levels in roots of two barley (Hordeum vulgare L.) cultivars differing in salt tolerance (cv CM 72, tolerant; cv Prato, sensitive) was analyzed using two-dimensional polyacrylamide gel electrophoresis. Preliminary experiments indicated that germination of Prato was inhibited significantly in the presence of NaCl, but growth of the surviving Prato seedlings was not substantially different from that of CM 72. Fluorographs of two-dimensional gels containing in vivo labeled polypeptides or in vitro translation products were computer analyzed to identify and quantitate changes that resulted when plants were grown in the presence of 200 millimolar NaCl for 6 days. The patterns of in vivo labeled polypeptides and in vitro products of CM 72 and Prato were qualitatively the same. Salt caused quantitative changes in numerous polypeptides and translatable mRNAs, but, overall, the changes were relatively small. Salt did not induce the synthesis of unique polypeptides or translatable mRNAs and did not cause any to disappear. Because of the similarities of the two cultivars with respect to growth and polypeptide patterns and the slight changes in polypeptide and translation product levels caused by salt, specific polypeptides or translatable mRNAs that are related to salt tolerance in barley could not be identified.