Characterizations of rhizobial clones compatible with G. max cv. JD17. (a) Compatible clones harbor insertion mutations in the conserved T3SS gene cluster. Sequences around individual insertion sites are conserved among three test strains, and all insertion sites are herein indicated in the T3SS gene cluster of 25509 by vertical lines (orange: 25509; light green: 83666; blue: 05631) either above (mutations in Tn5 mutants) or below (mutations in evolved clones) the DNA strands. The number in the bracket indicates the number of independent clones harboring the mutation in the same site. Tripartite regions within this T3SS cluster and genes of known functions within each region are indicated. Coding sequences on either forward (gray) or reverse (black) strand of 25509 symbiosis plasmid are shown. (b) Insertion mutation of T3SS was mainly mediated by IS (insertion sequence) among Tn5 mutants (19/21) and evolved clones with spontaneous mutations (SP; 15/16). The number of re-sequenced clones are shown. (c) The number of pink nodules on G. max cv. JD17 and G. soja WSD induced by four wild-type strains (45436, 83666, 25509 and 05631 represented in red, green, yellow and blue, respectively), 21 Tn5 mutants (05631Tn5, 83666Tn5 and 25509Tn5 mutants listed in Supplementary Table 3) and 16 SP clones (05631SP, 83666SP and 25509SP clones listed in Supplementary Table 4).