A TaqMan-based real time PCR assay for specific detection and quantification of Xylella fastidiosa strains causing bacterial leaf scorch in oleander.

A TaqMan-based real-time PCR assay was developed for specific detection of strains of X. fastidiosa causing oleander leaf scorch. The assay uses primers WG-OLS-F1 and WG-OLS-R1 and the fluorescent probe WG-OLS-P1, designed based on unique sequences found only in the genome of oleander strain Ann1. The assay is specific, allowing detection of only oleander-infecting strains, not other strains of X. fastidiosa nor other plant-associated bacteria tested. The assay is also sensitive, with a detection limit of 10.4fg DNA of X. fastidiosa per reaction in vitro and in planta. The assay can also be applied to detect low numbers of X. fastidiosa in insect samples, or further developed into a multiplex real-time PCR assay to simultaneously detect and distinguish diverse strains of X. fastidiosa that may occupy the same hosts or insect vectors. Specific and sensitive detection and quantification of oleander strains of X. fastidiosa should be useful for disease diagnosis, epidemiological studies, management of oleander leaf scorch disease, and resistance screening for oleander shrubs.

Research note: exceptional absolute pitch perception for spoken words in an able adult with autism.

Autism is a neurodevelopmental disorder, characterised by deficits in socialisation and communication, with repetitive and stereotyped behaviours [American Psychiatric Association (1994). Diagnostic and statistical manual for mental disorders (4th ed.). Washington, DC: APA]. Whilst intellectual and language impairment is observed in a significant proportion of diagnosed individuals [Gillberg, C., & Coleman, M. (2000). The biology of the autistic syndromes (3rd ed.). London: Mac Keith Press; Klinger, L., Dawson, G., & Renner, P. (2002). Autistic disorder. In E. Masn, & R. Barkley (Eds.), Child pyschopathology (2nd ed., pp. 409-454). New York: Guildford Press], the disorder is also strongly associated with the presence of highly developed, idiosyncratic, or savant skills [Heaton, P., & Wallace, G. (2004) Annotation: The savant syndrome. Journal of Child Psychology and Psychiatry, 45 (5), 899-911]. We tested identification of fundamental pitch frequencies in complex tones, sine tones and words in AC, an intellectually able man with autism and absolute pitch (AP) and a group of healthy controls with self-reported AP. The analysis showed that AC's naming of speech pitch was highly superior in comparison to controls. The results suggest that explicit access to perceptual information in speech is retained to a significantly higher degree in autism.

Lineage-specific decay of folate biosynthesis genes suggests ongoing host adaptation in phytoplasmas.

Phytoplasmas are nonculturable cell wall-less, obligate intracellular pathogens of plants and insect vectors. In their descent from walled bacterial ancestors, phytoplasmas underwent massive genome reduction, resulting in some of the smallest cellular genomes known in nonsymbiotic bacteria. While requirements for in vitro culture of phytoplasmas remain unknown, two opposing reports have appeared concerning genes encoding the ability of phytoplasmas to synthesize folates de novo. One study found pseudogene homologs of folP and folK, obviating folate synthesis in "Candidatus Phytoplasma asteris"-related strain CPh, whereas, a separate study found intact genes encoding a complete folate biosynthesis pathway in "Ca. Phytoplasma asteris"-related strain OY. To resolve the apparent conflict, we hypothesized that evolutionary adaptation to the availability of folate and/or other metabolites in host cells is an ongoing process in the phytoplasma clade that is reflected in part by differences among phytoplasmas in the status of genes of the folate biosynthesis pathway. By studying folP and folK loci in 11 closely related phytoplasmas, we determined that these essential folate biosynthesis genes are intact in some phytoplasmas but are deteriorating in closely related strains. We suggest that the status of the folate biosynthesis pathway and the course of gene decay are lineage-specific, predicting the eventual, lineage-related loss of recognizable folP and folK homologs in phytoplasma genomes.

Folate biosynthesis pseudogenes, PsifolP and PsifolK, and an O-sialoglycoprotein endopeptidase gene homolog in the phytoplasma genome.

Phytoplasmas are wall-less phytopathogenic prokaryotes of small genome sizes that are obligate parasites of insect vectors and plant hosts. We have cloned a clover phyllody (CPh) phytoplasma DNA locus containing five potential coding sequences. Two were identified as pseudogenes (PsifolP and PsifolK) homologous to folP and folK genes, which encode dihydropteroate synthase (DHPS) and 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK), respectively, in other bacteria. Evolution of the phytoplasma presumably involved loss of functions through the formation of these and other pseudogenes during adaptation to obligate parasitism. The findings suggest that the phytoplasma lacks capacity for de novo folate biosynthesis and possesses a transport system for absorption of preformed folate from host cells. The PsifolP-PsifolK region was flanked by three open reading frames (ORFs) encoding a DegV family protein, a hypothetical protein with a P60-like lipoprotein domain homologous with the P60-like Mycoplasma hominis protein, and a glycoprotease (Gcp) protein that possibly functions as a host adaptation or virulence factor.