CDNA ISOLATION AND GENE-EXPRESSION OF THE MAIZE ANNEXINS P-33 AND P35

The isolation, cloning, and sequencing of two full-length cDNAs corres ponding to the root tip forms of the maize (Zea mays L. cv Clipper) an nexins p33 and p35 are described. These are the first complete sequenc es for the widely reported doublet of plant annexins. The predicted se quences can be divided into four repeat domains characteristic of the annexin family, but Ca2+ binding by the type-II site typical of annexi ns would be predicted to occur only in repeats 1 and 4. This reduced n umber of sites is consistent with previously reported biochemical data indicating a high Ca2+ requirement for membrane association. Although the two annexins are very similar (80% amino acid identity), their ge nes are quite distinct, as demonstrated by their different 3' noncodin g regions and Southern blotting. The predicted sequences of the root t ip proteins are very similar to regions known from peptide sequencing of the coleoptile proteins. Because a rather small gene family is indi cated, the implication is that there may be less functional diversity than in animal cells. Furthermore, the sequence data clearly show that plant annexins form a very distinct group compared with those from ot her kingdoms.