MOLECULAR EVOLUTION OF MAIZE CATALASES AND THEIR RELATIONSHIP TO OTHER EUKARYOTIC AND PROKARYOTIC CATALASES

We have compared the nucleotide and protein sequences of the three mai ze catalase genes with other plant catalases to reconstruct the evolut ionary relationship among these catalases. These sequences were also c ompared with other eukaryotic and prokaryotic catalases. Phylogenies b ased on distances and parsimony analysis show that all plant catalases derive from a common ancestral catalase gene and can be divided into three distinct groups. The first, and major, group includes maize Cat1 , barley Cat1, rice CatB, and most of the dicot catalases. The second group is an apparent dicot-specific catalase group encompassing the to bacco Cat2 and tomato Cat. The third is a monocot-specific catalase cl ass including the maize Cat3, barley Cat2, and rice CatA. The maize Ca t2 gene is loosely related to the first group. The distinctive feature s of monocot-specific catalases are their extreme high codon bias at t he third position and low degree of sequence similarity to other plant catalases. Similarities in the intron positions for several plant cat alase genes support the conclusion of derivation from a common ancestr al gene. The similar intron position between bean catalases and human catalase implies that the animal and plant catalases might have derive d from a common progenitor gene sequence.