Similar to the situation in dinoflagellates, no apparent Smbinding site sequence was found in the predicted intron regions of either of the PmaSLRNAs. Instead, AUUCUGG (L-type) or AUCUGG (S-type) found within the SL was the only recognizable candidate Sm-binding site, as in the DinoSL (AUUUUGG). The predicted intron region was similar between the two Pma-SLRNAs, in contrast to the conserved intron in DinoSL RNAs, with the exception of the ancient parasitic genus of dinoflagellates Amoebophrya that showed considerable variation ( Figure 1B ). In the structural simulation using the default conditions for all but temperature, which was adjusted to the culture temperature of 27uC, the splice-donor dinucleotide ('gu' in 'Gguag') was doublestranded and the putative Sm-binding site (AUUCUGG/AU-CUGG) single-stranded, forming a small terminal loop. The simulation yielded one comparable structure for both types of PmaSLRNAs ( Figure 3 ). The predicted structures were similar to typical dinoflagellate SL RNA structures, having two stem-loops [8] , [9] , with the 'extra' intron region situated in a bulge of unpaired sequence connecting the two stem loops.