DIFFERENTIAL EXPRESSION OF THE 2 TYPES OF HISTONE-H2A GENES IN WHEAT

Five histone H2A cDNA clones have been isolated from a wheat cDNA libr ary. They were divided into two groups, termed type 1 and type 2, base d on their deduced amino acid sequences and their gene expression patt erns. Three type 1 clones had ORFs encoding proteins similar to angios perm histone H2As known so far, whereas two type 2 clones encoded an i dentical protein, which was more similar to Norway spruce (gymnosperm) H2A than to the angiosperm H2As. The C-terminus of the type 2 H2A was shorter than that of the type 1 H2As and lacked the characteristic SP KK motif that is conserved in angiosperm H2As. Northern analysis revea led that the mRNA levels of the type 1 HeA genes were high in prolifer ating cells during germination and in various tissues of young seedlin gs, while the mRNA levels of the type 2 genes were high in non-prolife rating cells in which the type 1 gene was poorly expressed. This resul t suggests that the expression of these two groups of H2A genes is dif ferently regulated during development in wheat.