Sequence analysis of avrXa7. (A) Schematic representation of the repeat domain of the avrXa7 gene product by using the single amino acid code for the twelfth and thirteenth codons of the repeat units. GenBank accession nos. for proteins are as follows: AvrXa7, AF275317; AvrXa10, AAA92974; AvrBs3, CAA34257; AvrBs3–2, S34809; Avrb6, AAB00675; PthA, AAC43587; PthN, AAB69865; PthB, AAD01494. (B) Unusual repeat thirteen of avrXa7. Duplicated region is underlined. Asterisks indicate positions of missing nucleotides or amino acid residues of the prototypic repeat unit.