Expression sites and developmental regulation of genes encoding (1→3,1→4)-β-glucanases in germinated barley.

Expression sites of genes encoding (1→3,1→4)-β-glucan 4-glucanohydrolase (EC 3.2.1.73) have been mapped in germinated barley grains (Hordeum vulgare L.) by hybridization histochemistry. A(32)P-labelled cDNA (copy DNA) probe was hybridized to cryosections of intact barley grains to localize complementary mRNAs. No mRNA encoding (1→3,1→4)-β-glucanase is detected in ungerminated grain. Expression of (1→3,1→4)-β-glucanase genes is first detected in the scutellum after 1 d and is confined to the epithelial layer. At this stage, no expression is apparent in the aleurone. After 2 d, levels of (1→3,1→4)-β-glucanase mRNA decrease in the scutellar epithelium but increase in the aleurone. In the aleurone layer, induction of (1→3,1→4)-β-glucanase gene expression, as measured by mRNA accumulation, progresses from the proximal to distal end of the grain as a front moving away from, and parallel to, the face of the scutellum.