Figure 1

<p> <i>Mu</i> insertion into <i>EXPB1</i> and its effect on Zea m 1 content of pollen. (a) Cartoon showing the structure of <i>EXPB1</i> and location of the <i>Mu</i> insertion (exons denoted with boxes). Also indicated are the locations of primers used for PCR screening. (b) <i>Mu</i> is inserted near the intron border flanking the fourth exon. (c) Portion of a 2-D gel image of wild type (<i>EXPB1</i>) pollen protein showing the Zea m 1 isoforms, which were identified by immunoblotting. (d) Relative amount of total Zea m 1 protein extracted from pollen of <i>EXPB1/EXPB1</i> and <i>expb1/expb1</i> plants. (Mean±SE; N = 2; t = 9.15; p = 0.035).</p

Figure 3

<p>Transmission rate of <i>expb1</i> as a function of the size of the pollen load from <i>EXPB1/expb1</i> plants (mean±SE, N = 4).</p

Figure 2

<p>Pollen viability and pollen performance <i>in vitro</i> and <i>in vivo</i>. (a) Percentage of viable pollen, based on staining with thiazolyl blue (mean±SE, N = 20–22 plants). (b) Micrograph of pollen stained with thiazolyl blue. Viable pollen stained dark purple. (c) Pollen tube growth <i>in vitro</i> (mean±SE, N = 20–22). Bars with different letters of the alphabet differ significantly using Tukey pairwise comparisons with the overall probability adjusted for multiple comparisons.</p

Figure 4

<p>Pollen tube from <i>EXPB1</i> pollen growing through ovary tissue for 22 h after pollination. Ovaries were stained with 0.1% aniline blue for 30 min and then examined under a fluorescence microscope.</p

Role of (1,3)(1,4)-β-Glucan in Cell Walls: Interaction with Cellulose

(1,3)­(1,4)-β-d-Glucan (mixed-linkage glucan or MLG), a characteristic hemicellulose in primary cell walls of grasses, was investigated to determine both its role in cell walls and its interaction with cellulose and other cell wall polysaccharides in vitro. Binding isotherms showed that MLG adsorption onto microcrystalline cellulose is slow, irreversible, and temperature-dependent. Measurements using quartz crystal microbalance with dissipation monitoring showed that MLG adsorbed irreversibly onto amorphous regenerated cellulose, forming a thick hydrogel. Oligosaccharide profiling using <i>endo</i>-(1,3)­(1,4)-β-glucanase indicated that there was no difference in the frequency and distribution of (1,3) and (1,4) links in bound and unbound MLG. The binding of MLG to cellulose was reduced if the cellulose samples were first treated with certain cell wall polysaccharides, such as xyloglucan and glucuronoarabinoxylan. The tethering function of MLG in cell walls was tested by applying <i>endo</i>-(1,3)­(1,4)-β-glucanase to wall samples in a constant force extensometer. Cell wall extension was not induced, which indicates that enzyme-accessible MLG does not tether cellulose fibrils into a load-bearing network