Genomic and evolutionary aspects of phytoplasmas

Kenro Oshima,Kensaku Maejima,Shigetou Namba

doi:10.3389/fmicb.2013.00230

Abstract

Parasitic bacteria that infect eukaryotes, such as animals and plants, often have reduced genomes, having lost important metabolic genes as a result of their host-dependent life cycles. Genomic sequencing of these bacteria has revealed their survival strategies and adaptations to parasitism. Phytoplasmas (class Mollicutes, genus ‘Candidatus Phytoplasma’) are intracellular bacterial pathogens of plants and insects and cause devastating yield losses in diverse low- and high-value crops worldwide. The complete genomic sequences of four Candidatus Phytoplasma species have been reported. The genomes encode even fewer metabolic functions than other bacterial genomes do, which may be the result of reductive evolution as a consequence of their life as an intracellular parasite. This review summarizes current knowledge of the diversity and common features of phytoplasma genomes, including the factors responsible for pathogenicity.

Highlights

Phytoplasmas are plant pathogens of the bacterial class Mollicutes (Lee et al, 2000; Hogenhout et al, 2008)
Phytoplasmal epidemics among coconut palms have destroyed the livelihoods of many people in Africa and the Caribbean, who depend on the trees for nourishment, building materials, and income (Strauss, 2009)
The amyA gene was identified in the ‘Ca. P. asteris’ OY-M strain genome; as it contains a mid-sequence frameshift mutation leading to an early termination codon, the expected ORF is incomplete and is divided into two smaller ORFs (Oshima et al, 2004), suggesting that an ancestral phytoplasma may have possessed a functional copy of this gene

Summary

Introduction

Phytoplasmas (genus ‘Candidatus Phytoplasma’) are plant pathogens of the bacterial class Mollicutes (Lee et al, 2000; Hogenhout et al, 2008). The amyA gene was identified in the ‘Ca. P. asteris’ OY-M strain genome; as it contains a mid-sequence frameshift mutation leading to an early termination codon, the expected ORF is incomplete and is divided into two smaller ORFs (Oshima et al, 2004), suggesting that an ancestral phytoplasma may have possessed a functional copy of this gene.

Results

Conclusion