Functional Analysis Of Genes In LuxR Family Of Acidovorax Citrulli Ac-5 Strain

Lux R-type regulators are a widely studied group of bacterial helix-turn-helix(HTH) transcription factors involved in the regulation of many genes coding for important traits.Acidovorax citrulli is a seed-borne, Gram negative bacterium that causes bacterial fruit blotch of cucurbitaceous plants.Here we analyzed the structures of the Lux R-type regulators and studied their functions by generating mutants and completing biolocigal analyses. The overall goal of this research was to investigate the regulation of the A. citrulli Lux R-type regulators in the pathogenic mechanism of BFB in watermelon.1. Bioinformatics analysis of Lux R-type regulators in A. citrulliThe genomic analysis of the A. citrulii stains showed that a total number of 13 homologous proteins belong to Lux R family. These proteins have 4 types of domains. The amino acid alignment result showed that these 13 proetins are divied into 3 groups.2. Construction of the function gene deletion mutants and their corresponding complementary strainsIn order to elucidate the function of Lux R-type regulators in A. citrulli, seven genes mutations were constructed through using homologous recombinant. We also constructed their corresponding complementary strains.3. Role of Lux R-type regulators in A. citrulli virulenceVirulence tests showed that the differences between Ac-5 and mutants Δlux R-1121, Δlux R-3591, Δlux R-3862, Δlux R-4229 and Δlux R-4382 were statistically significant(P < 0.05). But for mutants Δlux R-1577(P = 0.27) and Δlux R-2460(P = 0.33), there were no significant differences in BFB index.4. Research on phenotypic characteristics of the Lux R gene mutantsSwimming motility for the seven mutants was significantly less than the WT strains(P < 0.01). With the exception of Δlux R-4382, all the mutants formed flagella like the WT strain. We observed the different express level(P < 0.01) in gene fli R and fli C in mutants. There was no obvious difference in typical twitching haloes around the colonies between the WT strain Ac-5 and mutant Δlux R-3591. Biofilm production by Δlux R-3591 was similar to that of the WT strain Ac-5, WT produced significantly less biofilm than the other mutants.