SDS-PAGE was performed to select the constructs expressing Imp or IdpA proteins of the proper size. The His-tagged Imp and IdpA proteins were purified from the E. coli cell extracts by chromatography on a nickel NTA column (Qiagen), according to previously described procedures (Kakizawa et al., 2004). The purified proteins were used to immunize rabbits for preparation of antisera. The IgG fractions were purified from the crude sera with a Protein A Sepharose CL-4B (GE Healthcare, Piscataway, NJ). Western blotting was performed according

to selleck chemicals previously described procedures (Kakizawa et al., 2009) using anti-Imp and anti-IdpA IgG purified from immunized rabbits. Immunohistochemical analysis was performed according to a previously described method (Arashida et al., 2008) with some modifications. Stem tissues were excised from PoiBI-infected ‘Jester Red’ and uninfected ‘Flaming Sphere’ poinsettias, fixed, embedded in Paraplast Plus (Sherwood Medical), and cut into 10-μm thick sections using a microtome. Anti-Imp and anti-IdpA IgG were used with an alkaline phosphatase-mediated reporter system to detect Imp and IdpA proteins in each tissue. These tissues were observed by Axio Imager microscopy (Carl Zeiss). To detect PoiBI in poinsettia plants, we extracted total DNA from 30 commercially

available poinsettia cultivars (Table 1) and amplified 1.3-kb DNA fragments containing the phytoplasma 16S rRNA gene by PCR. Of the 30 cultivars, all except ‘Annette Metabolism inhibitor Hegg Diva’, ‘Annette Hegg Marble’, ‘Eckespoint C-1 Red’,

and ‘Flaming Sphere’ yielded fragments of the expected size (Table 1). Sequencing of these fragments confirmed that their DNA sequences were identical to that of the 16S rRNA gene of PoiBI (Lee et al., 1997; GenBank Acc. No. 190223), indicating that these 26 cultivars were infected with PoiBI. Using total DNA isolated from the poinsettia cultivar ‘Primelo Jingle Bells’ as a template, we amplified a 6.0-kb DNA fragment containing the PoiBI imp gene, a 2.5-kb DNA fragment containing the PoiBI idpA gene, and a 3.3-kb DNA fragment between imp and idpA genes of the PoiBI DNA by LA-PCR (Fig. 1). Sequencing of these fragments yielded the complete DNA sequence of a 10-kb genomic region of PoiBI containing Vitamin B12 eight complete open reading frames and two partial open reading frames (Fig. 1). These genes (and their encoded proteins), listed in order, were rnc (RNAse III; partial gene only), dnaD (chromosome replication initiation protein), imp, pyrG (CTP synthase), psd (phosphatidylserine decarboxylase), pssA (phosphatidylserine synthase), rpoE (DNA-directed RNA polymerase δ subunit), dnaX (DNA polymerase III), idpA, and tRNA-Ser (serine transfer RNA; partial gene only). This gene structure is identical to that previously reported for WX strain (Liefting & Kirkpatrick, 2003; GenBank Acc. No. AF533231).