Publications

4495

‘Candidatus Liberibacter solanacearum’ is a plant pathogen affecting the families Solanaceae and Apiaceae in different parts of the world. ‘Ca. L. solanacearum’ is a Gram-negative, fastidious α-proteobacterium that is vectored by different psyllid species. Plant-pathogenic bacteria are known for interfering with the host physiology or defense mechanisms, often by secreting bacterial effectors. Effector proteins are critical for virulence; therefore, the identification of effectors could help with disease management. In this study, we characterized the Sec-translocon-dependent ‘Ca. L. solanacearum’–hypothetical protein effector 1 (Lso-HPE1). We compared this protein sequence in the different ‘Ca. L. solanacearum’ haplotypes. We predicted the signal peptide and validated its function using Escherichia coli’s alkaline phosphatase fusion assay. Agrobacterium tumefaciens-mediated transient expression in Nicotiana benthamiana demonstrated that Lso-HPE1 from ‘Ca. L. solanacearum’ haplotypes A and B were able to inhibit the induction of cell death in plants. We also compared gene expression of the Lso-HPE1- transcripts in ‘Ca. L. solanacearum’ haplotypes A and B in tomato and in the vector Bactericera cockerelli. This work validates the identification of a Sec-translocon-dependent ‘Ca. L. solanacearum’ protein possibly involved in suppression of plant cell death.

‘Candidatus Liberibacter asiaticus’ (Las) is an unculturable α-proteobacterium associated with citrus huanglongbing (HLB), a devastating disease currently threatening the citrus industry worldwide. Here, we present the genome sequence of Las strain TaiYZ2 from an HLB-affected pomelo tree in Hat Yai district, Songkhla Province, Thailand. The TaiYZ2 genome is composed of 1,230,623 bp with G+C content of 36.4%. This is the first Las genome sequence from Thailand, which will enrich current Las genome resource and facilitate HLB research and management.

‘Candidatus Liberibacter asiaticus’ is the unculturable causative agent of citrus huanglongbing disease. Here, we report the first citrus root metagenome sequence containing the draft genome of ‘Ca. L. asiaticus’ strain AHCA17, obtained from a pummelo tree in California. The assembled genome was 1.2 Mbp and resulted in 37 contigs (N50 = 158.7 kbp) containing 1,057 predicted open reading frames and 45 RNA-coding genes. This draft genome will provide a valuable resource in further study of ‘Ca. L. asiaticus’ genome diversity and pathogen epidemiology.