Sinorhizobium as a model system to study Liberibacter gene regulators
S. LONG (1), M. Barnett (1) (1) Department of Biology, Stanford University, U.S.A.

Ca.Liberibacter asiaticus (CLas) is the causative agent of citrus greening disease. Multiple approaches should be taken to finding antibacterial agents, including in vivo assays of function. Because CLas cannot be grown in culture, we are using a closely related bacterium (Sinorhizobium meliloti) as a heterologous host to assay function of key CLas proteins. We hope to develop a high-throughput screen to look for compounds that inhibit critical CLas functions. We developed a system for strong, inducible expression of CLas genes in S. meliloti. A key feature of this system is the use of synthetic CLas open reading frames (2) whose codon usage is optimized for expression in S. meliloti. Optimized sequences encoding CLas transcriptional regulators RpoH1, VisN/VisR, LdtR, LsrB, PhrR, and CtrA were synthesized and cloned into pSRK-Gm (3) controlled by an IPTG-inducible lac promoter. In parallel, we constructed S. meliloti deletion mutants lacking the orthologous S. meliloti gene; the resulting, strains should exhibit activity due to the introduced CLas regulators. This was completed for all except ctrA, which encodes an essential gene in S. meliloti (1). Phenotypic assays show that CLas regulators restore function to S. meliloti mutants. We have completed global transcription analyses for S. meliloti expressing CLas rpoH and ldtR.

Abstract Number: S1-4
Session Type: Special Session