The members of clusters containing proteins from all ten species were regarded as conserved splicing-related proteins. The members of clusters only containing proteins from a particular species or clade were regarded as candidates of species/clade specific proteins. The uniqueness of these specific proteins was verified based on results of BLASTp searches (cutoff e-value of 10^-20) against proteins from all available plant species both at the PlantGDB and NCBI BLAST servers. All candidates with significant similarity to proteins from other species were removed, and the retained candidates were regarded as species/clade specific splicing-related proteins.
By looking through tables, 67 Arabidopsis specific proteins, 10 dicots specific proteins, and 44 moss missing proteins were identified and classified into different families according to sequence and domain comparison. The uniqueness to corresponding specis/clade was verified by BLASTp search against other available plants in PlantGDB.