Atta, Sagheer

‘Candidatus Liberibacter asiaticus’ (CLas) is a pathogen causing Huanglongbing (HLB, yellow shoot disease), which is highly destructive to citrus production. The CLas strains harbor prophages. We identified two unique prophages, designated as P-PA19-1 and P-PA19-2, in CLas strain PA19 from Pakistan using next-generation sequencing analysis. P-PA19-1 prophage has high sequence similarity (identity: 78.23%) at the early-gene region of prophage SC1 (Type 1), but it is significantly divergent in the late-gene region (identity: 62.03%). P-PA19-2 was highly similar to SC2 (Type 2) in the late gene region (identity: 97.96%), and also in the early gene region except for a deletion of a 7,179-bp nucleotide sequence that contains a CRISPR/cas system in SC2. Both P-PA19-1 and P-PA19-2 had circular plasmid forms, and only P-PA19-2 was found integrated in the PA19 chromosome. The two new prophages were only found in Pakistani samples. Identification of prophages enhances our understanding of CLas genomic diversity and also the biology and evolution of CLas prophages.

‘Candidatus Liberibacter asiaticus’ (CLas) is an unculturable, phloem-restricted αProteobacteria, associated with citrus Huanglongbing (HLB), which is one of the most destructive diseases in citrus production worldwide. Here, we present the genome sequences of CLas strains PA19 and PA20 from HLB-affected kinnow trees in Multan, Punjab Province, Pakistan. The CLas genomes of PA19 and PA20 comprise 1,224,156 bp and 1,226,225 bp, respectively, with an average GC content of 36.4%. Both harbored the Type 2 prophage. In this study, we report two CLas genomes from Pakistan, which extends the sequence database of CLas and will contribute to CLas biology and HLB management.