Table 1. Enrichment and association of retrotransposons with phylogentically more primitive intronless IFNs in X. laevis.

IFN gene	Associated Retrotransposon (RT)	% of RT within IFN gene-centered region	Phylogenic relevance (%)
XaIFN1	3 3′-LTR/Gypsy	1.9 (Chr9_10S)	N/A
XaIFN3	1 5′-LTR/Gypsy
XaIFN7	2 3′-LTR/Gypsy
XaIFNX1	2 3′-NonLTR/Tx1;
1 3′-LTR/Gypsy		5.7 (Chr9_10L)	60.5%
XaIFNX5	2 3′-NonLTR/Penelope
XaIFNX6	1 3′-LTR/DIRS
XaIFNX9	1′ 5′-NonLTR/L1
XaIFNX10	1′ 3′-NonLTR/L1
XaIFNX11	1′ 3′-LTR/Gypsy
XaIFNX18	2 5′-NonLTR/CR1
XaIFNX19	2 3′-LTR/DIRS; 5 3′-LTR/Gypsy	15 (Chr3L)	76.2%
XaIFNX20	1 5′-LTR/Gypsy
XaIFNX21	1 3′-LTR/Gypsy
XaIFNX22	2 5′-LTR/Gypsy; 4 3′-LTR/Gypsy
XaIFNLX1	4 3′-LTR/DIRS	9.4 (Chr3L)	N/A
XaIFNLX2	n/a
XaIFNL1	1 3′-NonLTR/L2	5.2 (Chr8S)	70.0%
XaIFNL2	1 3′-LTR/Gypsy
XaIFNL3	1 3′-LTR/Gypsy
XaIFNL4	1 3′-LTR/Gypsy
XaIFNL5	1 5′-LTR/Gypsy
XaIFNL6	1 3′-NonLTR/Penelope
XaIFNL8	2 5′-NonLTR/Penelope; 1 5′-LTR/Gypsy