Figure 1. Gene organization of rdr1, rdr2, rdr3 and rdr4.

Positions of exons (boxes) and introns (solid lines) were determined by comparisons of genomic and cDNA sequences for each gene (see text). Black boxes indicate regions corresponding to the RdRP domains in the encoded RDR proteins. Three alternatively spliced sequences were identified in rdr4, each predicted to result in a truncated RdRP domain because of premature stop codons indicated by asterisks. Lengths are indicated above and below exons and introns, respectively.