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 µmol/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.