Immunodominant membrane proteins of phytoplasmas

Abstract

Phytoplasmas are plant-pathogenic, phloem-colonizing, cell wall-less microorganisms that are primarily dependent on insect transmission for their spread and survival. The life cycle of phytoplasmas involves replication in insects and host plants. Until recently, phytoplasmas have resisted all attempts at cultivation in cell-free media, making these pathogens poorly characterized on a physiological and biochemical basis. However, host-pathogen relationships can be studied by investigating immunodominant membrane proteins (IDPs), which are located on the exterior surfaces of phytoplasma cells and are the most abundant proteins of the cell membrane. These membrane proteins come in direct contact with both insect and plant hosts and are thought to play a crucial role in phytoplasma spread both within the plant and by insect vectors. Therefore, there is great interest in studying this class of proteins. We summarize and discuss important investigations about these membrane proteins, which have already provided a better understanding of the host-phytoplasma relationship.

Evidence suggesting interactions between immunodominant membrane protein Imp of Flavescence dorée phytoplasma and protein extracts from distantly related insect species

“…Interestingly, positive selection acting on phytoplasma MP has been suggested as a key feature in the adaptation of the pathogen to different hosts (Fabre et al ). Strong antigenic properties, previously described for extracellular domains of IDPs (Konnerth et al ), were also confirmed here for FD‐D Imp. Indeed, preliminary unpublished data confirm that the polyclonal serum, raised against the Imp recombinant domain in this study, resulted in specific recognition of the corresponding native full‐length protein in field samples (E. Angelini, pers.…”

“…SecY), adhesins, ATP‐dependent proteases and those encoded by potential mobile units and plasmids. However, a number of studies focused on the IDPs, since they are the most abundant proteins of the cell surface of phytoplasmas (for an overview see Konnerth et al ). Previous studies showed that two (Immunodominant membrane protein (Imp) and Antigenic membrane protein (Amp)) of the three nonhomologous immunodominant MP are involved in interactions between the phytoplasma cell surface and insect proteins (Suzuki et al ; Siampour et al , ; Galetto et al ; Rashidi et al ).…”

Multiple guests in a single host: interactions across symbiotic and phytopathogenic bacteria in phloem‐feeding vectors – a review

“…A crucial phase of the transmission process is the protein interaction between pathogen cells and those of the host, regulating pathogen crossing of gut and salivary gland epithelia. The main strategy for bacterial internalization reported for plant pathogenic agents is endo‐exocytosis (Kwon et al., ; Hogenhout et al., ; Cicero et al., ), mediated by various membrane proteins (Labroussaa et al., , ; Béven et al., ; Duret et al., ; Konnerth et al., ; Arricau‐Bouvery et al., ). The absence of specific adhesion machinery to host cells seriously weakens the vector competence (Weintraub & Beanland, ).…”

‘Candidatus Phytoplasma platensis’, a novel taxon associated with daisy (Bellis perennis) virescence and related diseases in South America

“…The resulting tree had the same topology as the generated by 16S rRNA and ribosomal protein genes, supporting the separation of BellVir phytoplasma (Figure 3). Immunodominant proteins would not be correlated with that of 16Sr DNA; however, imp is a gene well conserved over a wide range of phytoplasmas and can reflect in between phytoplasma differences regarding host range and vector transmission [35]. Phytoplasmas immunodominant proteins have been classified into three distinct types: (i) immunodominant membrane protein (Imp); (ii) immunodominant membrane protein A (IdpA); and (iii) antigenic membrane protein (Amp) [36].…”