The mini-exon genes of three Phytomonas isolates that differ in plant tissue tropism

Abstract

The tandem mini-exon gene repeat is an ideal diagnostic target for trypanosomatids because it includes sequences that are conserved absolutely coupled with regions of extreme variability. We have exploited these features and the polymerase chain reaction to differentiate Phytomonas strains isolated from phloem, fruit or latex of various host plants. While the transcribed regions are nearly identical, the intergenic sequences are variable in size and content (130-332 base pairs). The mini-exon genes of these phytomonads can therefore be distinguished from each other and from the corresponding genes in insect trypanosomes, with which they are oft confused.

PCR amplification of the spliced leader gene for the diagnosis of trypanosomatid parasites of plants and insects in methanol-fixed smears

“…2 (smaller box), the £agellates from coconut trees (Hart 1, Plt2 and Plt4) were found to di¡er from the £agellates of oil palms (March1and Plt5) by one C/T substitution. In addition, it was demonstrated that the sequences of the £agellates from coconut trees of French Guyana, as determined by Sturm et al [7] (Hart 1*) and by us (Hart 1), di¡ered by one extra T from the sequences of their counterparts from eastern Brazil (Plt2 and Plt4). As a further con¢rmation of the utility of the smear method, we sequenced the Phy-SLPCR amplicon derived from the smear of the gut of a laboratory reared insect (Ins1) fed on tomatoes infected with Phytomonas serpens at the laboratory (Plt1).…”

“…Hart1* and Hart1, £agellates from coconut trees of French Guyana; Plt2 and Plt4, £agellates from coconut trees of eastern Brazil; March 1 and Plt5, £agellates from oil palms of Colombia ; P. serpens, £agellates from tomatoes; Ins1, £agellates from an insect fed on tomatoes infected with P. serpens. Hart1* corresponds to the sequence reported by Sturm et al [7]; P. serpens corresponds to the sequence reported by Nunes et al [12]. trypanosomatids occurred (row a).…”

“…After comparing the sequences of the SL gene of various species of Phytomonas [7,12], we designed a 19-nt probe (SL3P), complementary to a conserved sequence of the SL gene. After testing this probe with a large number of trypanosomatids, we found that it hybridized exclusively with species of the genus Phytomonas [13].…”

5S Ribosomal RNA Gene Repeat Sequences Define at Least Eight Groups of Plant Trypanosomatids (Phytomonas spp.): Phloem‐Restricted Pathogens Form a Distinct Section

“…For example, the Spliced Leader (SL) RNA gene, also known as the mini‐exon gene, has emerged as a pivotal marker for diverse groups of protozoa in the kinetoplastid/euglenoid lineage (Campbell et al 1997). The transcribed region may be used as a marker to distinguish Phytomonas from insect trypanosomatids (Serrano et al 1999b; Serrano et al 1999c; Teixeira et al 1996) and the DNA sequence of the non‐transcribed spacer region may be used to distinguish among phloem, latex, and fruit isolates (Nunes et al 1995; Sturm et al 1995). Here we extend our studies on the tandemly‐repeated genes of kinetoplastid protozoa by investigating the 5S ribosomal RNA (rRNA) gene as a molecular marker.…”

Diversidade, relações filogenéticas e taxonomia de Phytomonas spp.

“…Phytomonas (Nunes et al, 1995;Sturm et al, 1995) e seu alinhamento com sequências de tripanossomatídeos de outros gêneros permitiram identificar uma sequência gênero-específica de 19 nucleotídeos, denominada SL3', complementar a região +40 a +59 do íntron do SL RNA. Vários estudos demonstraram a eficiência de uma sonda baseada na sequência SL3' na identificação de…”