Transcriptome analysis reveals a complex array of differentially expressed genes accompanying a source‐to‐sink change in phytoplasma‐infected sweet cherry leaves

Sweet cherry (Prunus avium) in China has recently been affected by a destructive disease that is characterised by symptoms of floral virescence and witches'-broom growths. The etiological agent of the disease is a subgroup 16SrV-B phytoplasma that is closely related to 'Candidatus Phytoplasma ziziphi.' A previous study revealed that photosynthetic activity had significantly declined in symptomatic leaves of the diseased sweet cherry trees. For a deeper view into the infection, we performed a comparative transcriptomic analysis. A total of 62,410 unigenes were identified; among them, 1,675 were differentially expressed in symptomatic leaves of diseased versus asymptomatic leaves of healthy plants. Phytoplasma infection induced the up-regulation of a suite of genes involved in carbohydrate metabolism, fatty acid biosynthesis, phenylpropanoid biosynthesis and flavonoid biosynthesis. Expression profiles of genes related to amino acid metabolism, hormone metabolism, and signal transductions were also altered in leaves of phytoplasma-infected trees. Findings from this study offer clues to understanding host responses to the phytoplasma infection and disease induction in sweet cherry trees. The constellation of differentially regulated genes identified in the present study may be explored as biomarkers for early detection of phytoplasma infection and as potential targets for disease control.