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

Abstract

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. K E Y W O R D S phytoplasma infection, Prunus avium, transcriptome

Integration of metabolomics and existing omics data reveals new insights into phytoplasma-induced metabolic reprogramming in host plants

“…Elevated levels of maltotetraose, glucose, and glucose 6-phosphate in SCV-IL samples may indicate an enhancement of glycolysis in sweet cherry trees upon phytoplasma infection. This result is consistent with the upregulated expression of glycolytic genes in our previous transcriptomic analysis [20] and other existing omics data (S3 Table ).…”

“…As a product of SPBase, enhanced sedoheptulose 7-phosphate may inhibit SPBase activity by negative feedback, a key regulatory feature of metabolism. Besides elevated sedoheptulose 7-phosphate, expression of the gene encoding glucose-6-phosphate 1-dehydrogenase (a key enzyme of the PPP) was also upregulated in SCV phytoplasma-infected leaves of sweet cherry trees based on our previous transcriptomics study [20]. These data pointed to a phytoplasma-induced increase in PPP activity in host plants.…”

“…Mock inoculation using healthy scions was also carried out. According to the procedures described in our previous study, symptom development was observed, and SCV phytoplasma infection was confirmed by PCR amplification and subsequent sequence analysis [20]. Leaf samples from three SCV phytoplasma-infected seven-year-old sweet cherry trees exhibiting typical witches'-broom symptom and three mock-inoculated healthy controls were used as three independent biological replicates, respectively.…”

“…Various high-throughput "omics" approaches developed in the recent years such as transcriptomics (quantitative analysis of mRNA transcripts), proteomics (analysis of protein composition), and metabolomics (identification and quantification of cellular metabolites) have been widely employed in the study of plant-phytoplasma interactions. So far, a total 23 of omics studies targeting phytoplasma-plant interactions have been reported, which include 10 transcriptomics [13,20,[28][29][30][31][32][33][34][35], 7 proteomics [36][37][38][39][40][41][42], 3 metabolomics [43][44][45], and 3 mixed omics studies [14,15,46]. These studies mainly focused on Bois Noir (BN), Flavescence dorée (FD), paulownia witches'-broom (PaWB), and jujube witches'-broom (JWB) phytoplasma-infected grapevine, paulownia, and jujube plants.…”

“…Sweet cherry virescence (SCV) phytoplasmas [group 16SrV, subgroup B (16SrV-B)] have been identified as the etiologic agent for this destructive disease [17][18][19]. Physiological and transcriptomic analyses have demonstrated that SCV phytoplasma-infected leaves experienced a complex array of metabolic alterations accompanying a source-to-sink functional change, which could profoundly impact the nutrition of both the phytoplasmas and host trees [17,20]. In this study, we took a metabolomics approach to examine SCV phytoplasma induced cellular metabolite changes in leaves of sweet cherry trees.…”