Origin of exon skipping-rich transcriptomes in animals driven by evolution of gene architecture

Table 1 Intron mean lengths and densities in ancestral eukaryotic genomes

Ancestor	Ancestral mean intron length (bp)	Introns/CDS kbp	Introns/gene	Source intron densities
LECA	–	4.3	6.11	Csűrös et al. 2011 [26]
Uropisthokonta	328	5.1	7.25	Csűrös et al. 2011 [26]
Urholozoa	481	5.52	7.86	Grau-Bové et al. 2017 [27]
Urichthyosporea (Chromosphaera, Creolimax, Sphaeroforma)	263	5.53	7.86	Grau-Bové et al. 2017 [27]
Urichthyophonida (Creolimax, Sphaeroforma)	393	6.98	9.92	Grau-Bové et al. 2017 [27]
Urmetazoa (animals)	845	8.8/8.7	12.51/12.37	Csűrös et al. 2011 [26]/Grau-Bové et al. 2017 [27]
Urporifera (sponges)	451	8.63	12.27	Grau-Bové et al. 2017 [27]
Urcnidaria	1016	8.3	11.80	Csűrös et al. 2011 [26]
Urbilateria	1342	7.7/7.7	10.94/10.94	Csűrös et al. 2011 [26]/Grau-Bové et al. 2017 [27]
Urprotostomia	891	7.4	10.52	Csűrös et al. 2011 [26]
Urecdysozoa	623	7.4	10.52	Csűrös et al. 2011 [26]
Urdeuterostomia	1710	7.7	10.94	Csűrös et al. 2011 [26]
Urvertebrata	3117	7.2	10.23	Csűrös et al. 2011 [26]
Urembryophyta (land plants)	313	6.4	9.10	Csűrös et al. 2011 [26]
Urchlorophyta (all unicellular/colonial green algae)	299	3.4	4.83	Csűrös et al. 2011 [26]
Trebouxiophyceae + Chlorophyceae (Chlorella, Volvox, Chlamydomonas)	–	6.2	8.82	Csűrös et al. 2011 [26]

Mean intron lengths estimated from phylogenetically independent comparisons of descendant species (see “Methods”; Additional file 1: Figure S24). Intron densities (taken from [26, 27]) are reported as introns/CDS kbp and introns/gene (by multiplying by the average CDS length [1422 kbp] of all organisms in our dataset; Additional file 1: Figures S1 and S2)

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