Figure 2. Purple top symptom is due to plant anthocyanin biosynthesis.

(a) Typical samples of healthy and OY-W infected rosette leaves of Arabidopsis chs mutant. Experimental conditions on phytoplasma-infection and observation were the same to Fig. 1a, b. Bar = 1 cm. (b) Expression analyses of anthocyanin synthesis genes, CHS and DFR, in Arabidopsis and Petunia. Transcriptional levels were obtained by qRT-PCR in healthy and OY-W-infected leaves. Each bar represents the average of three biological replicates(±SE). The average expression levels of healthy leaves were set as 1.0. Significant differences between healthy and infected leaves are indicated as * (P < 0.05) or ** (P < 0.01).