Biochemical changes in Oenothera biennis plants infected by 'Candidatus Phytoplasma solani'

The aim of the present paper was to study the response of Oenothera biennis L. to 'Candidatus Phytoplasma solani' (Stolbur) infection by analyzing total sugars, polyphenols, photosynthetic pigments content and the antioxidant capacity in leaves and roots of healthy and infected plants. The infection caused a significant increase in peroxidation of lipids, phenylalanine ammonia-lyase activity, total sugar, polyphenols and anthocyanins content (2.8, 2.6, 1.8, 1.4, 6.8 fold, respectively), as well as a decrease in photosynthetic pigments (2-6 fold) and total flavonoids (1.5 fold) in the leaves of Oe. biennis. Changes in these parameters were insignificant in the roots except for the total polyphenols content that was 2.7 times higher in the infected ones. Reduced gluthatione content in both tested organs was not affected by the infection (3.7 and 1.7 mu mol/g fresh weight of leaves and roots, respectively). The elevated content of total sugars, flavonoids and polyphenols, as well as the reduction of photosynthetic pigments and anthocyanins in infected plants are indicative of changes in the metabolism of Oe. biennis affected by the Stolbur phytoplasma. In addition to reduction of chlorophyll and carotenoids, the phytoplasma accelerated leaf senescence. Plants responded to the infection via enhanced superoxide anion scavenging, even though this reaction did not prevent, apparently, membrane damage in analysed leaves. This investigation presents new data on the effect of a phytoplasma infection on its host

Phytoplasmas: An Introduction

Phytoplasmas are among the most recently discovered plant pathogens. They are wall-less prokaryotes restricted to phloem tissue, associated with diseases affecting several hundred plant species. The impact of phytoplasma diseases on agriculture is impressive and, at the present day, no effective curative strategy has been developed. The availability of rapid and sensitive techniques for phytoplasma detection as well as the possibility to study their relationship with the host plants is a prerequisite for the management of phytoplasma-associated diseases

The Family Acholeplasmataceae (Including Phytoplasmas)The Prokaryotes

The family Acholeplasmataceae was originally established to accommodate the genus Acholeplasma, comprising the mollicutes that could be cultivated without the supplement of cholesterol and that use UGA as a stop codon instead of coding for tryptophan. It was later shown that the phytoplasmas, a large group of uncultivable, wall-less, non-helical mollicutes that are associated with plants and insects, shared taxonomically relevant properties with members of the genus Acholeplasma. Being not cultivable in vitro in axenic culture, the phytoplasmas could not be classified using the standards used for other mollicutes and are named using the category of Candidatus, as “Ca. Phytoplasma.” Although phytoplasmas are associated with habitats and ecology different from acholeplasmas, the two genera Acholeplasma and “Candidatus Phytoplasma” are phylogenetically related and form a distinct clade within the Mollicutes. The persisting inability to grow the phytoplasmas in vitro hinders the identification of their distinctive phenotypic traits, important criteria for mollicute classification. Until supplemental phenotypic traits become available, the genus “Candidatus Phytoplasma” is designated, on the basis of phylogeny, as a tentative member in the family Acholeplasmataceae. Phylogenetic analysis based on gene sequences, in particular, ribosomal sequences, has provided the major supporting evidence for the composition and taxonomic subdivision of this group of organisms with diverse habitats and ecology and has become the mainstream for the Acholeplasmataceae systematics. However, without the ability to determine phenotypic properties, the circumscription of related species among the non culturable members of the family remains a major issue. The genus Acholeplasma comprises 14 species predominantly associated with animals and isolated from mammalian fluids but regarded as not normally pathogenic. Conversely, the genus “Ca. Phytoplasma” includes plant pathogens of major economic relevance worldwide. To date, 36 “Ca. Phytoplasma species” have been described