ARS | Publication request: EXPRESSION OF FUNGAL THERMOTOLERANT (1,3-1,4)-BETA-GLUCANASE IN TRANSGENIC BARLEY SEEDS DURING GERMINATION

Submitted to: Plant Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 5, 1999
Publication Date: N/A

Interpretive Summary: One of the main problems limiting the ability to develop certain barley cultivars for malting and other industrial applications is that they may contain high levels of beta-glucans (fiber components), which are not broken down sufficiently during processing or during seed germination. One way to overcome this problem is to cause the seeds to produce more beta-glucanase enzyme, which breaks down the beta-glucans. However, the native enzyme is often in short supply or unable to withstand the high temperatures required in some processes. We have overcome this problem by introducing a new gene into barley so that it produces a heat-stable beta- glucanase enzyme. The gene encoding the enzyme was previously constructed so that it would only be turned on when the seed is germinating. The new enzyme produced by the seed is very stable. The enzyme can withstand 2 hours of exposure to 65 degrees C., with no loss of activity, whereas 80% of the native barley glucanase enzyme is destroyed. This development will initially have the greatest impact on the malting and brewing industries by providing potential low-glucan barley extracts. This also has potential use in the sweetener industry, and the same technology can also be adapted to produce small grains with better characteristics for poultry feed.

Technical Abstract: The gene for a thermotolerant endo-beta-glucanase from Trichoderma reesei was used to genetically transform the elite Finnish barley cultivar Kymppi and the non-malting barley cultivar Golden Promise. Only one transgenic plant resulted from particle bombardment-mediated transformation of Kymppi, whereas 250 bombarded Golden Promise embryos produced 37 plants. Extracts from the transformed barley seeds maintained 100% of glucanase activity after incubation for 2 hours at 65 degrees C. However, in untransformed seeds, the activity of native glucanase was reduced by 80%. The gene was cloned behind an alpha-amylase promoter so that it would be turned on during germination, in response to induction by the phytohormone gibberellin.