Kakizawa, Shigeyuki

ABSTRACT The complete genome, 226,287 bps in size, of “ Candidatus Nardonella sp.” Pin-AIST, an obligatory bacterial endosymbiont of the black hard weevil Pachyrhynchus infernalis , was sequenced. The extremely reduced endosymbiont genome is specialized for tyrosine synthesis, which contributes to the hardness of the beetle’s exoskeleton.

ABSTRACT The complete genome, 173,958 bp in size, of “ Candidatus Carsonella ruddii” DC-OKEB1 , an obligate bacterial endosymbiont of the Asian citrus psyllid Diaphorina citri , was determined. The genome sequence provides valuable information for comparative and evolutionary aspects of the intimate insect–microbe mutualism.

ABSTRACT Phytoplasmas are unculturable plant-pathogenic bacteria causing devastating damage to agricultural production worldwide. Here, we report the draft genome sequence of “ Candidatus Phytoplasma asteris” strain OY-V. Most of the known virulence factors and host-interacting proteins were conserved in OY-V. This genome furthers our understanding of genetic diversity and pathogenicity of phytoplasmas.

SUMMARY Phytoplasmas are plant‐pathogenic bacteria that are associated with numerous plant diseases. We have previously reported the complete genomic sequence of Candidatus Phytoplasma asteris, OY strain, OY‐M line, which causes mild symptoms. The phytoplasma genome lacks several important metabolic genes, implying that the consumption of metabolites by phytoplasmas in plants may cause disease symptoms. Here we show that the approximately 30‐kb region including the glycolytic genes was tandemly duplicated in the genome of OY‐W phytoplasma, which causes severe symptoms. Almost duplicated genes became pseudogenes by frameshift and stop‐codon mutations, probably because of their functional redundancy. However, five kinds of genes, including two glycolytic genes, remained full‐length ORFs, suggesting that it is advantageous for the phytoplasma to retain these genes in its lifestyle. In particular, 6‐phosphofructokinase is known as a rate‐limiting enzyme of glycolysis, implying that the different number of glycolytic genes between OY‐W and OY‐M may influence their respective glycolysis activities. We previously reported that the phytoplasma population of OY‐W was higher than that of OY‐M in their infected plants. Taking this result into account, the higher consumption of the carbon source may affect the growth rate of phytoplasmas and also may directly or indirectly cause more severe symptoms.