Comparison of non-mutant and mutant waxy genes in rice and maize

The waxy gene, which is responsible for the synthesis of amylose in endosperm and pollen, is genetically well characterized in many grasses including maize and rice. Homology between the previously cloned maize waxy gene and the rice gene has facilitated our cloning of a 15-kb HindIII fragment that contains the entire rice gene. A comparison of the restriction maps of the maize and rice genes indicates that many restriction sites within translated exons are conserved. In addition, the rice gene encodes a 2.4-kb transcript that programs the in vitro synthesis of a 64-kD pre-protein which is efficiently precipitated with maize waxy antisera. We demonstrate that these gene products are altered in rice strains containing mutant waxy genes. Southern blot analysis of 16 rice strains, ten containing waxy mutations, reveals that the waxy gene and flanking restriction fragments are virtually identical. These results contrast dramatically with the high level of insertions and deletions associated with restriction fragment length polymorphism and spontaneous mutations among the waxy alleles of maize.