Submitted to: Proceedings International Barley Genetics Symposium
Publication Type: Proceedings
Publication Acceptance Date: 9/1/2000
Publication Date: N/A
Interpretive Summary: For the last several years, the major malting barley-producing area of the U.S. has been plagued by the disease Fusarium head blight or scab. This cereal disease is generally caused by the fungi F. graminearum and/or culmorum. Studies with wheat have shown that the proteins in diseased kernels are partially destroyed, implying that the fungus uses these grain proteins for its growth. To use these grain proteins, the fungus must produce enzymes that break them down into pieces that it can digest. We are studying an enzyme (proteinase) that the fungus may use for degrading the barley proteins. We have shown that three Fusarium species produced such proteinases. There are also small proteins in barley grain ('inhibitors') that can stop the proteinase from functioning and these may help to protect the grain from the blight. We have isolated and characterized the proteinase that F. culmorum produces when grown on grain and we have separated and partially purified a group of proteinase inhibitors from barley. The inhibitors will be studied further to determine how they interact with the fungal proteinase and this will clarify whether the proteinase inhibitors can be manipulated to improve the resistance of barley to fungal attack. This information will directly benefit barley breeders and researchers who can study whether the inhibitors really do increase the resistance of barley plants to head blight and, if so, breeders can use it to produce more resistant barley varieties. The availability of Fusarium-resistant barley lines will help the malting and brewing industries by ensuring that they have sufficient malting barley at all times and will help barley producers by allowing them to produce malting quality barley even if some Fusarium is present.
Technical Abstract: We are studying one of the major barley disease problems, Fusarium head blight, that is currently plaguing the North American barley industry, by applying biochemical methods. To do this, we are searching for a way to make it harder for the fungus to successfully attack the plant. This blight or scab is a common cereal disease that is generally caused by F. graminearum and/or culmorum. When the Fusarium attacks the plant it may need to degrade some of the cell wall proteins to get into the grain and/or after it gets into the developing head it probably needs to hydrolyze some of the storage proteins to use for food. We have shown that three Fusarium species produced alkaline proteinases when grown on media that contained either wheat gluten or autoclaved barley grain and have also demonstrated that there are small proteins in barley grain that can inhibit the activities of these proteinases. It seemed likely that these inhibitor proteins might play roles in protecting the grain from fungal diseases. This paper reports the purification and partial characterization of the proteinase that is synthesized by F. culmorum and shows that it is inhibited by proteins from barley. The inhibitors have been extracted and separated into fractions by column chromatography. When they are completely purified and identified, their interactions with the purified proteinase will be studied and the most effective of them will be studied in depth. After this proteinase-inhibitor system has been sufficiently characterized, it may be possible to manipulate the inhibitors to develop barleys that have improved resistance to invasion and colonization by the Fusarium fungi.