U12 type introns were lost at multiple occasions during evolution

BMC Genomics

Table 2 Summary of U12 introns identified in a range of eukaryotic species.

	Number of ESTs analyzed	U12 spliceosomal RNAs	U12 AT-AC introns (5' rule)		U12 GT-AG introns (5' rule)		U2 GC-AG introns		U2 GT-AG introns		Other AT-AC introns
			B	S	B	S	B	S	B	S	B	S
Trichinella spiralis	25,268	+	3 (3)	3 (3)	1 (1)	13 (8)	217	217	14697	14685	5	5
Monosiga brevicollis	29,495	-	0	0	0	1 (0)	134	134	13327	13326	10	10
Rhizopus oryzae	13,313	+	1 (1)	1 (1)	2 (2)	3 (2)	71	71	5520	5519	3	3
Phycomyces blakesleeanus	47,847	+	9 (8)	8 (8)	8 (8)	12 (10)	446	446	13504	13500	31	32
Phakopsora pachyrhizi	34,394	-?	0	0	0	1 (0)	10	10	561	560	2	2
Acanthamoeba castellanii	13,784	+	1 (0)	0	1 (1)	3 (0)	21	21	1232	1230	2	2
Entamoeba histolytica	14,388	-	0	0	0	0	0	0	160	160	4	4
Physarum polycephalum	25,393	+	83 (14)	27 (15)	88 (57)	218 (109)	34	34	6452	6326	251	307
Chlamydomonas reinhardtii	202,044	-	0	0	0	0	532	532	25053	25053	7	7
Phytophthora infestans	94,091	+	2 (2)	2 (2)	1 (1)	1 (1)	66	66	6601	6601	9	9
Phytophthora sojae	28,467	+	2 (2)	2 (2)	1 (1)	1 (1)	34	34	3351	3351	5	5
Thalassiosira pseudonana	61,913	-	0	0	0	0	37	37	5140	5140	13	13
Phaeodactylum tricornutum	133,871	-	0	0	0	0	23	23	3815	3815	7	7

Table shows prediction according to methods of Burge et al (B) and Sheth et al (S) [11]. The "5' rule" is that 5' splice site sequence is RTATCCTT where one of the Cs in positions +5 and +6 may be converted into a T. Occurrence of U12 snRNAs is from Davila-Lopez et al [8]. For sequences of U12 introns as predicted by the Burge et al method, see additional file 2.

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