Characterization of a maize beta-amylase cDNA clone and its expression during seed germination

Immunoglobulin E-specific allergens against leaf in serum of dogs with clinical features of grass leaf allergy

BACKGROUND

Grass leaf has been suspected of causing immunoglobulin (Ig)E-mediated immediate hypersensitivity reactions in humans and dogs. However, most studies in this area are case-control studies without in vitro data showing the involvement of IgE in the reaction. Laboratory studies have demonstrated the reactivity to a 50-55 kDa protein with clinical signs immediately after contact with grass leaf material. The clinical findings of dogs with atopic-like dermatitis immediately after contact with grass leaf material suggest the involvement of grass leaves as the allergen source.

OBJECTIVES

This study was designed to test the IgE-reactivity of grass leaf proteins in dogs with clinical signs and positive scratch test results against grass leaf material.

MATERIALS AND METHODS

The serum of 41 patients with a history of allergy and suspected to grass leaf material was immunoblotted against grass leaf extracts from five suspected grass species. The IgE-positive blots were separated with 2D gel electrophoresis and analysed with mass spectrometry (MS). Commercially supplied proteins were used to validate immunoblot activity.

RESULTS

The serum of 25 dogs diagnosed with grass dermatitis had positive IgE-specific immunoblot against one or more grass leaf extracts. The MS data indicated a reactive band at 55 kDa to be beta-amylase or RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) large subunit (RbLS). All tested dog sera showed IgE-reactivity with beta-amylase and some with RbLS.

CONCLUSIONS AND CLINICAL RELEVANCE

Canines with clinical signs of grass-related dermatitis had IgE-reactivity against grass leaf proteins. Serum IgE-reactivity to beta-amylase and RuBisCO large subunit may indicate that these proteins act as allergens, possibly causing pruritus and skin lesions.

Marine antifouling from thin air

The dynamic relationship between the settlement behaviour of marine biota (cells, spores, larvae) and the longevity of an entrapped air layer (plastron) on submersed superhydrophobic surfaces was systematically investigated. Plastron lifetime decreased with increasing hydrophobic polymer loadings, and was correlated with the settlement rate of a range of fouling species of varying length scale, motility and hydrophobic/hydrophilic surface preference. The results show that the level of fouling on immersed superhydrophobic surfaces was greater when plastron lifetimes were minimal, regardless of the length scale, motility and the surface preference of the organisms. This is the first direct demonstration of the broad-spectrum attachment-inhibiting properties of a plastron on an immersed superhydrophobic surface.

A novel biofilm channel for evaluating the adhesion of diatoms to non-biocidal coatings

Laboratory assessment of the adhesion of diatoms to non-toxic fouling-release coatings has tended to focus on single cells rather than the more complex state of a biofilm. A novel culture system based on open channel flow with adjustable bed shear stress values (0-2.4 Pa) has been used to produce biofilms of Navicula incerta. Biofilm development on glass and polydimethylsiloxane elastomer (PDMSe) showed a biphasic relationship with bed shear stress, which was characterised by regions of biofilm stability and instability reflecting cohesion between cells relative to the adhesion to the substratum. On glass, a critical shear stress of 1.3-1.4 Pa prevented biofilm development, whereas on PDMS, biofilms continued to grow at 2.4 Pa. Studies of diatom biofilms cultured on zwitterionic coatings using a bed shear stress of 0.54 Pa showed lower biomass production and adhesion strength on poly(sulfobetaine methacrylate) compared to poly(carboxybetaine methacrylate). The dynamic biofilm approach provides additional information to supplement short duration laboratory evaluations.

Specific elements of the glyoxylate pathway play a significant role in the functional transition of the soybean cotyledon during seedling development

BACKGROUND

The soybean (Glycine max) cotyledon is a specialized tissue whose main function is to serve as a nutrient reserve that supplies the needs of the young plant throughout seedling development. During this process the cotyledons experience a functional transition to a mainly photosynthetic tissue. To identify at the genetic level the specific active elements that participate in the natural transition of the cotyledon from storage to photosynthetic activity, we studied the transcript abundance profile at different time points using a new soybean oligonucleotide chip containing 19,200 probes (70-mer long).

RESULTS

After normalization and statistical analysis we determined that 3,594 genes presented a statistically significant altered expression in relation to the imbibed seed in at least one of the time points defined for the study. Detailed analysis of this data identified individual, specific elements of the glyoxylate pathway that play a fundamental role during the functional transition of the cotyledon from nutrient storage to photosynthesis. The dynamics between glyoxysomes and peroxisomes is evident during these series of events. We also identified several other genes whose products could participate co-ordinately throughout the functional transition and the associated mechanisms of control and regulation and we described multiple unknown genetic elements that by association have the potential to make a major contribution to this biological process.

CONCLUSION

We demonstrate that the global transcript profile of the soybean cotyledon during seedling development is extremely active, highly regulated and dynamic. We defined the expression profiles of individual gene family members, enzymatic isoforms and protein subunits and classified them accordingly to their involvement in different functional activities relevant to seedling development and the cotyledonary functional transition in soybean, especially the ones associated with the glyoxylate cycle. Our data suggests that in the soybean cotyledon a very complex and synchronized system of control and regulation of several metabolic pathways is essential to carry out the necessary functions during this developmental process.

The {beta}-amylase genes of grasses and a phylogenetic analysis of the Triticeae (Poaceae)

There are two forms of β-amylase in the Triticeae crop plants wheat, barley, and rye: an endosperm-specific form encoded by two or three closely linked genes, and a tissue-ubiquitous form encoded by a single gene. Both rice and corn have one ubiquitously expressed form encoded by a single gene. This study focuses on two phylogenetic analyses of β-amylase gene sequences. First, a phylogenetic analysis of coding sequences from wheat, barley, rye, rice, and corn was expected to clarify the relationship between the endosperm-specific and tissue-ubiquitous forms of the protein. Instead, it illustrates possible effects of distant outgroups, based on conflicting patterns of character state variation consistent with different root positions. Next, a broad sample of the monogenomic Triticeae was included in a phylogenetic analysis based on sequences from a portion of the tissue-ubiquitous β-amylase gene. The results were compared to existing Triticeae gene trees, among which extensive conflict had been noted in the past. One additional gene tree has not completely clarified the complexity of the group, but has shed additional light on reticulate phylogenetic patterns within the tribe, including relationships involving Eremopyrum, Thinopyrum, and the Triticum/Aegilops group.

Expression of beta-amylase from alfalfa taproots

Alfalfa (Medicago sativa L.) roots contain large quantities of beta-amylase, but little is known about its role in vivo. We studied this by isolating a beta-amylase cDNA and by examining signals that affect its expression. The beta-amylase cDNA encoded a 55.95-kD polypeptide with a deduced amino acid sequence showing high similarity to other plant beta-amylases. Starch concentrations, beta-amylase activities, and beta-amylase mRNA levels were measured in roots of alfalfa after defoliation, in suspension-cultured cells incubated in sucrose-rich or -deprived media, and in roots of cold-acclimated germ plasms. Starch levels, beta-amylase activities, and beta-amylase transcripts were reduced significantly in roots of defoliated plants and in sucrose-deprived cell cultures. beta-Amylase transcript was high in roots of intact plants but could not be detected 2 to 8 d after defoliation. beta-Amylase transcript levels increased in roots between September and October and then declined 10-fold in November and December after shoots were killed by frost. Alfalfa roots contain greater beta-amylase transcript levels compared with roots of sweetclover (Melilotus officinalis L.), red clover (Trifolium pratense L.), and birdsfoot trefoil (Lotus corniculatus L.). Southern analysis indicated that beta-amylase is present as a multigene family in alfalfa. Our results show no clear association between beta-amylase activity or transcript abundance and starch hydrolysis in alfalfa roots. The great abundance of beta-amylase and its unexpected patterns of gene expression and protein accumulation support our current belief that this protein serves a storage function in roots of this perennial species.

Amylases synthesis in scutellum and aleurone layer of maize seeds

The endosperm of germinating maize seeds contains four isozymes of alpha-amylases (alpha-amylase-1 to -4) and one isozyme of beta-amylase. The alpha-amylases were purified by affinity chromatography on amylose and separated by DEAE-cellulose chromatography, into two groups, namely alpha-amylases-1,2 and alpha-amylases-3,4; and beta-amylase was purified by precipitation as a glycogen-enzyme complex. The molecular weight of alpha-amylases-1 and -2 was 46 kD, alpha-amylases-3 was 44.5 kD and of alpha-amylases-4 was 47.5 kD. The molecular weight of beta-amylase was 56 kD. During seed germination increase in amylolytic activity in endosperm was mainly contributed by secretion of alpha-amylases from adjoining aleurone layer and scutellum. The synthesis and secretion of alpha-amylases was first initiated in the scutellum followed by aleurone layers. Exogeneous Ca2+ stimulated synthesis of alpha-amylases in both eleurone layer and scutellum. In contrast, though scutellum and aleurone layer synthesized beta-amylase but it was not secreted to the medium. These results suggest that during the early germination period, alpha-amylases secreted from scutellum mobilizes starch.