pl1-Rhoades(mum9515) is an RNA null. Reverse transcriptase–PCR analysis of seedling RNA. pl1: spliced, 171 bp; unspliced, 281 bp. aat: spliced, 290 bp; unspliced, 454 bp (not shown). Negative controls: −RNA, full assay in absence of RNA; H2O, no template in PCR stage only.