PMV genome and cDNA mutants for replication assays. The PMV genome map shows six open reading frames (ORFs), as filled rectangles. The solid line represents the 4,326 nucleotide single-stranded plus-sense PMV genomic RNA (gRNA). Four proteins (p8, p6.6, p15, and CP) are encoded from the subgenomic RNA (sgRNA), which initiates at nucleotide 2851 (bent arrow). Both p48 and p112 are expressed from the gRNA from an AUG start codon at nt 29–31. The UAG (amber) read-through codon is indicated with an asterisk (*). The speckled region indicates the conserved domain (CD), from amino acids 306–405, encoded on both p48 and p112. Two replicase mutants, pRT-Stop and pAmb-Tyr, express p48 or p112, respectively. The Apa I sites were used to delete nucleotides 3129 to 3400 on the PMV cDNA. This deletion abolished the expression of p6.6, p15, and CP on the sgRNA to create pKB238. Another construct, pMAX6  with a point mutation to abolish translation of the p8 ORF, was digested with Apa I and religated. This created pQP94, a construct that no longer expressed any of the sgRNA encoded genes.