Relative expression level of lao gene in different strains determined by qRT-PCR [26].

Rf-1: wild type; B1 and B19: two mutants of wild type Rf-1 with transposon-inserted sdmT gene and nhaD gene, respectively; B1/M and B19/M: both mutant B1 and mutant B19 with blank delivery vector pBBR1MCS-5; B1/MS and B19/MN: mutant B1 and mutant B19 with complementary plasmid pBBR1MCS-5/sdmT carrying entire gene of sdmT and plasmid pBBR1MCS-5/nhaD carrying entire gene nhaD, respectively. Mean difference of relative expression of lao gene between different strains was statistically analyzed by ANOVA (S3 Dataset and S4 Dataset). “***” is extremely significant (P<0.001).