Phloem-restricted phytoplasmas impair carbon fixation in tomato

Phytoplasmas are prokaryotic obligated parasites of plants that colonize the sieve elements of their host plant, causing alterations in phloem function such as occlusion, nutrients uptake and utilization, impairment of photosynthesis and photo assimilates translocation. Symptoms have been well described and include inhibition and decline of photosynthesis efficiency and alterations in sugar metabolism. Our research group has been investigating the effects of ‘Candidatus Phytoplasma solani’ infection on tomato plants (Solanum lycopersicum cv. Micro-Tom) by RNA-sequencing. Analyzing tomato plants grown under different Fe regimes, we demonstrated that infection changes Fe distribution in leaves, affects photosynthetic machinery and perturbs shootto- root communication. Moreover, infection impacts mineral nutrient fluxes and alters ion homeostasis of K, Ca, Mg, Fe and Mn. Here, we focus our analysis on the transcriptional regulation of genes involved on carbon fixation and carbon metabolism. A gene co-expression network was investigated with a weighted correlation approach implemented in the R package WGCNA. Gene expression and protein analysis highlighted key genes of carbon fixation pathway and confirmed impairment of carbon metabolism.