Research Information System
Uluslararası Katılımlı IX. Bitki Koruma Kongresine, Ankara, Turkey, 3 - 05 September 2025, pp.58, (Summary Text)
Spiroplasma citri are Gram-positive bacteria with motile helical cells that lack a cell
wall. S. citri is recognized as the pathogen of Citrus Stubborn Disease
and horseradish brittle root disease, but it can also cause diseases of
carrots, sesame and various ornamentals and weeds. In the Mediterranean region,
this intracellular pathogen is spread from plant to plant by the leafhopper
vector Circulifer haematoceps. The successful spread of S. citri
depends on the mediation of receptor-ligand interactions by S. citri
adhesins and the crossing of the intestinal epithelium and salivary gland
barrier by endocytosis from the insect haemocoel. P89 (SARP1), one of the two adhesin proteins
thought to be responsible for adhesion and invasion in host cells in terms of
spiroplasma-host interaction, was analyzed in detail by sequence and structure
in this study. P89 homologs were investigated in the genomes of S. citri
strains that had been cultured for many years and were obtained from various
plants and insects in our recent field studies. Their distribution in the
genome and plasmids was examined, and the differences between orthologs and
paralogs were determined at the sequence level. It was observed that in some
culture samples, P89 genes lost their plasmid positioning, integrated into the
chromosome and transformed into pseudogenes, unlike in recently collected
insect and plant strains. Using the amino acid sequences of P89 homologues, 3D protein models
were constructed by using AlphaFold 3 application and it was determined that
P89 homologues showed a multi-domain protein structure in which beta-propeller,
beta-sandwich, ubiquitin-like and spiralin-like domains were connected to each
other sequentially. Various structural variations were also observed between
the domains of P89 homologues in the strains we examined and the possible
effects of these variations on spiroplasma-host interactions were examined. The
results obtained in this study will provide a model for how different S.
citri strains invade host cells and cross cellular barriers in terms of
spiroplasma-host interactions.
Keywords:
Spiroplasma, P89, adhesin, host
interaction