Figure 4

A model of carbohydrate metabolism in phytoplasma infected grapevine tissues. In addition, unlike the genomes of two strains of 'Ca. P. asteris' [5, 6] that of 'Ca. P. australiense' has a complete gene for sucrose phosphorylase (Suph, [8]). The enzyme is important for sucrose cleavage into glucose-1-phosphate and fructose. It might be possible, therefore, that the 'BN' phytoplasma, which belongs to the same taxonomic stolbur group as 'Ca. P. australiense', also possesses the gene for sucrose phosphorylase. How the enzyme degradation products might be further utilized by phytoplasmas is currently not known. Expression of genes that are represented in rounded rectangles was experimentally measured by qRT-PCR in both growing season (first growing season to the left and second growing season to the right of the gene symbol). Gene expression is color coded (yellow color represents up-regulation and blue color down-regulation in infected vs. healthy samples). VvInv2 encodes vacuolar acid invertase 2, VvSuSy encodes sucrose synthase, VvGlc1 and VvGlc2 encode two 1.3-β-glucanases, VvCaSy encodes callose synthase, VvAgpL encodes large subunit of ADP-glucose pyrophosphorylase and Suph encodes phytoplasmic sucrose phosphorylase.