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The phytopathogenic mollicute-insect vector interface: a closer look
Abstract:
ABSTRACT Spiroplasma citri, transmitted by phloem-feeding leafhoppers, moves from the gut lumen through the gut wall, hemolymph, and salivary glands and multiplies in insect tissues. Nontransmissible lines were deficient in their ability to cross these barriers. Molecular analysis revealed extensive chromosomal rearrangements between the transmissible and nontransmissible spiroplasma lines including a large chromosomal inversion and deletions of about 10 kb at each inversion border. One open reading frame of the deleted region, cloned from the transmissible strain BR3-3X, encodes an integral membrane protein of 58 kDa that shares limited sequence similarity with major adhesin proteins of two zoopathogenic mycoplasmas. Adhesion of spiroplasmas to cultured leafhopper cells was inhibited by proteases, suggesting that adherence to host cells is mediated by spiroplasma membrane protein(s). A hypothetical model for insect transmission of phytopathogenic mollicutes is presented.
Insights
Spiroplasma citri transmission relies on its ability to cross insect barriers, linked to chromosomal rearrangements. A specific membrane protein appears crucial for adherence to leafhopper cells.
Area of Science:
- Plant pathology
- Insect microbiology
- Molecular biology
Background:
- Spiroplasma citri is a phytopathogenic mollicute transmitted by leafhoppers.
- Transmission involves the pathogen moving through insect tissues and barriers.
Purpose of the Study:
- To investigate the molecular basis of Spiroplasma citri transmission.
- To identify factors enabling Spiroplasma citri to cross insect barriers.
Main Methods:
- Comparative molecular analysis of transmissible and nontransmissible Spiroplasma citri lines.
- Identification and characterization of chromosomal rearrangements.
- Cloning and analysis of a specific open reading frame encoding a membrane protein.
- In vitro adhesion assays using cultured leafhopper cells and protease treatment.
Main Results:
- Transmissible Spiroplasma citri lines possess chromosomal rearrangements, including inversions and deletions, absent in nontransmissible lines.
- A deleted region in transmissible strains contains an open reading frame encoding a 58 kDa integral membrane protein.
- This protein shows similarity to adhesins of zoopathogenic mycoplasmas.
- Spiroplasma adhesion to leafhopper cells is mediated by membrane proteins and inhibited by proteases.
Conclusions:
- Chromosomal rearrangements are associated with Spiroplasma citri transmissibility.
- A specific membrane protein likely plays a key role in Spiroplasma adherence to and crossing of insect host barriers.
- This research contributes to understanding phytopathogenic mollicute transmission mechanisms.
