Figure 1. Intron and splice site features of plant introns. (a) Intron size in Arabidopsis thaliana; (b) Number of introns per gene in Arabidopsis thaliana; (c) Schematic representation of two exons and one intron (red bar). The graphics show the frequencies of every base in each position (intronic bases are marked with “I” and exonic bases with “E”). Twelve bases (six exonic, six intronic) were retrieved from all exon–intron borders reported in Arabidopsis; (d) Consensus sequence of the exon–intron borders of Arabidopsis, human and roundworm. All data for Arabidopsis are according to the annotation available in TAIR9 (http://www.arabidopsis.org/). The consensus sequences of exon–intron borders of human and roundworm were obtained from Ref. [ 6].

Figure 2. Arabidopsis SR protein gene families and complexity. The domain structure and family members are presented for gene families with othologs in human (SF2/ASF, 9G8, and SC35) and plant‐specific families (SCL, RS, and RSZ).