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A characteristic feature of grasses and commercially important cereals is the presence of (1,3;1,4)-beta-d-glucans in their cell walls. We have used comparative genomics to link a major quantitative trait locus for (1,3;1,4)-beta-d-glucan content in barley grain to a cluster of cellulose synthase-like CslF genes in rice. After insertion of rice CslF genes into Arabidopsis, we detected (1,3;1,4)-beta-d-glucan in walls of transgenic plants using specific monoclonal antibodies and enzymatic analysis. Because wild-type Arabidopsis does not contain CslF genes or have (1,3;1,4)-beta-d-glucans in its walls, these experiments provide direct, gain-of-function evidence for the participation of rice CslF genes in (1,3;1,4)-beta-d-glucan biosynthesis.

Three structural classes of (1-->3)-beta-D-glucans are encountered in some important soil-dwelling, plant-associated or human pathogenic bacteria. Linear (1-->3)-beta-glucans and side-chain-branched (1-->3,1-->2)-beta-glucans are major constituents of capsular materials, with roles in bacterial aggregation, virulence and carbohydrate storage. Cyclic (1-->3,1-->6)-beta-glucans are predominantly periplasmic, serving in osmotic adaptation. Curdlan, the linear (1-->3)-beta-glucan from Agrobacterium, has unique rheological and thermal gelling properties, with applications in the food industry and other sectors. This review includes information on the structure, properties and molecular genetics of the bacterial (1-->3)-beta-glucans, together with an overview of the physiology and biotechnology of curdlan production and applications of this biopolymer and its derivatives.

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The location of the (1→3)-β-glucan, callose, in the walls of pollen tubes in the style of Nicotiana alata Link et Otto was studied using specific monoclonal antibodies. The antibodies were raised against a laminarinhaemocyanin conjugate. One antibody selected for further characterization was specific for (1→3)-β-glucans and showed no binding activity against either a cellopentaose-bovine serum albumin (BSA) conjugate or a (1→3, 1→4)-β-glucan-BSA conjugate. Binding was inhibited by (1→3)-β-oligoglucosides (DP, 3-6) with maximum competition being shown by laminaripentaose and laminarihexaose, indicating that the epitope included at least five (1→3)-β-linked glucopyranose residues. The monoclonal antibody was determined to have an affinity constant for laminarihexaose of 2.7. 10(4)M(-1). When used with a second-stage gold-labelled, rabbit anti-mouse antibody, the monoclonal antibody probe specifically located the (1→3)-β-glucan in the inner wall layer of thin sections of the N. alata pollen tubes.

SummaryMonoclonal antibodies were raised against a (1-~3,1~4)-~-glucan-bovine serum albumin (BSA) conjugate. One antibody (BG1) selected for further characterization, was specific for (1--~3,1--~4)-~-giucan, displaying no binding activity against a (l~3)-~-glucan-BSA conjugate and minimal binding against a cellopentaose-BSA conjugate. A range of oligosaccharides was prepared by enzymatic digestion of (1-~3,1-~4)-13-glucan, purified by size exclusion chromatography and characterized by 1H-NMR and anion exchange chromatography.These (l~3,1~4)-13-oligogiucosides, together with (1-~3)-~-and (l~4)-~-oligoglucosides were used to characterize the binding site of the monoclonal antibody (BG1) by competitive inhibition. The monoclonal antibody showed maximal binding to a heptasaccharide with the structure GIc(1~3) GIc(1 ~4) GIc(1 -~4) GIc(1 ~3) GIc(1 ~4) Gic(1-->4) GIc and was determined to have an affinity constant of 3.8 x 104 M -1 for this oligoglucoside.The monoclonal antibody (BG1) has been used to develop a sensitive sandwich ELISA for the specific quantitation of (l~3,1~4)-13-glucans. The assay operates in the range 1-10 ng m1-1 and shows no significant cross-reaction with tamarind xyloglucan, wheat endosperm arabinoxylan or carboxymethylpachyman ((1-~3)-13-glucan). When used with a second-stage, rabbit anti-mouse gold conjugate and viewed under the electron microscope, the monoclonal antibody probe was found to bind strongly to the walls of the aleurone in thin sections of immature wheat (Triticum aestivum) cv. Millewa grains but not to the middle lamella region. A previously described

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