Expression of the Spiroplasma citri spiralin gene in Escherichia coli. Use of the recombinant plasmid carrying this gene as a molecular probe.

Expression in Escherichia coli of the cloned Spiroplasma citri spiralin gene results in the expression of a 30.5-kDa protein serologically related to spiralin. A protein with the same properties is also present in minor amounts in S. citri cells, suggesting that spiralin is first produced as a preprotein containing a signal polypeptide, which is removed during further processing. Hybridization experiments have demonstrated that pES1, the recombinant plasmid carrying the spiralin gene, can be used as a molecular probe, allowing the detection of S. citri DNA in infected plants and in insect cell cultures.