POLY(A) TAIL SHORTENING OF ALPHA-AMYLASE MESSENGER-RNAS IN VEGETATIVETISSUES OF ORYZA-SATIVA

The pattern of expression for the entire alpha-amylase gene family in rice vegetative tissues during the developmental growth stages has bee n studied. We were surprised that the size of rice alpha-amylase mRNAs in the young roots, shoots, and different tissues from adult plant wa s shorter by approximately 250 bases than that in immature or mature e mbryos and aleurone layers of seed. Interestingly, the difference in t he size of the alpha-amylase mRNAs of rice seed and vegetative tissues is due to the variation in the length of the 3'-poly(A) tracts. In ad dition, if without glycogen-precipitated treatment for alpha-amylase p urification, no alpha-amylases can be detected in vegetative tissues b y Western blot analysis. Furthermore, in vitro translation assay revea led that alpha-amylase mRNAs receiving shortened poly(A) tracts in veg etative tissues become translationally repressed. These results indica te that the 3'-poly(A) tract of eukaryotic mRNAs plays an important ro le in controlling mRNA translatability. (C) 1994 Academic Press, Inc.