Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2002
Publication Date: 8/2/2002
Citation: Fu, J., Abebe, T., Federico, M.L., Kaeppler, H.F., Skadsen, R.W. 2002. Expression of a seed-specific antifungal protein hordothionin gene is inhibited in the leaves of transgenic barley and oat at the pre- and post-translational levels. Proceedings of American Society of Plant Biologists Annual Meeting. p. 61. Interpretive Summary:
Technical Abstract: Alpha-hordothionin is specifically produced in developing barley endosperms. Purified hordothionin protein has antimicrobial activity against a wide range of pathogenic bacteria and fungi in vitro as demonstrated by our group and others. We previously reported that the mRNA level of the hordothionin gene in leaves of transgenic barley harboring the hordothionin cDNA of nearly full length was extremely low and that an element in the transcribed region of the hordothionin gene may negatively regulate the mRNA level of a hordothionin-thioredoxin fusion gene in E. coli. Accordingly, the negative element was deleted. The altered hordothionin gene was ligated between a maize ubiquitin promoter and a nos termination sequence in pAHC25. The resulting construct was used to transform barley and oat via particle bombardment. Five independent barley transgenic lines (169 plants from about 200 regenerated plants) and 15 oat transgenic lines (65 plants from about 300 regenerated plants) were grown in the greenhouse. The hordothionin mRNA levels in the transgenic plants harboring the altered gene were many-fold greater than those in the transgenic plants harboring the unaltered gene. Even though the mRNA occurred on membrane-bound polyribosomes and was found in the expected size range of polyribosomes in the leaves of transgenic plants, no hordothionin protein could be detected. Thus, expression of this seed-specific gene in leaves appears to be inhibited by a two-fold mechanism, one involving sequence elements in the transcribed region that limit mRNA production or stability and another that limits translation product stability.