Abstract
Expansins are small proteins that play a key role in modifying the structure of the cell wall duringvarious physiological processes, in particular cell growth by elongation. Expansins are encoded by a largemultigene family and are divided into four subfamilies, the main ones being alpha- and beta-expansins; thelatter have received special development in cereals. Expansins are thought to modify the interactions of cel-lulose with xyloglucan (alpha-expansins) or with arabinoxylan (beta-expansins). At the same time, expansinsdo not have catalytic activity, the specific mechanism of their action is unclear, same as the physiological sig-nificance of such a wide variety of isoforms. To study the expression patterns of individual expansins, we con-ducted a transcriptomic analysis of all expansin genes identified in the maize genome using a convenientmodel system—zones of the maize growing primary root that differ in the stage of cell development and thecomposition of their cell walls. Of the 91 maize expansin genes, 67 were expressed in the root, and mostexpansin genes were characterized by a narrow range of zones with maximum transcript levels. Using a gly-coarray containing 183 polysaccharides from the cell walls of plants of various species, we demonstrated thatrecombinant expansins AtEXPA1 and AtEXPB1 are able to bind to arabinogalactans and rhamnogalacturo-nans I and a number of other cell wall polysaccharides, which expands the list of their potential carbohydratetargets. Differences in the specificity of the interaction of alpha- and beta-expansins with various polysaccha-rides, both quantitatively and qualitatively, have been demonstrated. It has been hypothesized that the abun-dance of expansins in one plant organism and the fine regulation of their expression can be explained, at leastin part, by the specific binding of individual expansins to specific cell wall polysaccharides.