In the July-September 2015 period of our work, we have continued to finish strain constructions and have begun Affymetrix GeneChip experiments in order to examine expression of transcripts in host Sinorhizobium meliloti due to introduced Candidatus Liberibacter asiaticus (CLas) transcription factor genes. Previously we showed that the cloned CLas rpoH gene can complement phenotypes of an S. meliloti double rpoH1 rpoH2 deletion mutant. We have now isolated total RNA from the S. meliloti rpoH1H2 mutant strain expressing CLas rpoH and prepared labeled cDNA. Controls for this experiment are: S. meliloti rpoH1H2 carrying the empty vector, pSRK-Gm; and S. meliloti rpoH1H2 carrying S. meliloti rpoH1, cloned in pSRK-Gm. All samples (3 biological replicates of each of 3 strains) have been submitted to our campus facility for hybridization to the S. meliloti genome chip, which will reveal the total transcriptome arising from CLas rpoH expression. Beyond rpoH, we intend to study 6 transcription factors from CLas . As described in the previous report, we are creating S. meliloti host strains with deletions for each of the S. meliloti genes corresponding to those CLas regulators, so we can optimally measure function of the introduced CLas genes. As of July report, we had constructed the visRN and ldtR mutants. We have since constructed an lsrB mutant. The S. meliloti lsrB deletion strain grows poorly. Using the cloned CLas lsrB gene carried on plasmid pSRK-Gm, we showed that induced expression of CLas lsrB partly rescues the poor growth phenotype of the S. meliloti mutant. We are encouraged that this shows at least partial function of CLas LsrB in S. meliloti. We are working on construction of a double phrR1 and phrR2 mutant; meanwhile we have introduced the cloned CLas phrR gene into wild type S. meliloti, in case we are unable to make the phrR1 phrR2 double mutant.. Construction of a ctrA deletion strain requires an extra step, since ctrA is essential for S. meliloti viability. Our progress to date includes successful cloning of the CLas and S. meliloti ctrA genes in vector pSRK-Gm. Each of these plasmids was introduced into S. meliloti containing a single crossover of the ctrA deletion construct. In parallel, we have constructed wild type S. meliloti strains containing the cloned CLas and Sm ctrA genes. We will screen these two strains (overexpressing either CLas ctrA or S. meliloti ctrA) in parallel on sucrose. If the optimized CLas ctrA gene does not allow for viability of a S. meliloti ctrA deletion strain, then we will study the CLas CtrA regulator in wild type S. meliloti.