Figure 2. Avr3b is induced during infection and shows transcriptional polymorphisms.

(A) Avr3b transcript levels in different developmental and infection stages measured by real-time RT-PCR. Total RNA was extracted from mycelia (MY), zoospores (ZO), cysts (CY), germinating cysts (GC), and infected soybean leaves at 6 hours post-infection (hpi), 12 hpi, and 24 hpi. All inoculations for RNA isolation were performed on susceptible soybean cultivar Williams. Real-time RT-PCR analysis employed primers specific for Avr3b and the actin gene. Transcrip level represent the P. sojae Avr3b mRNA levels compared with actin mRNA levels. Bars represent standard errors from 2 independent replicates each. (B) Avr3b transcriptional polymorphism between virulent (P7076) and avirulent (P6497) strains. Real-time RT-PCR analysis was conducted to compare Avr3b transcript levels at two infection-related stages, germinating cysts (GC) and infected leaves (24 hpi). Primers used in this assay amplified identical regions from Avr3b^P6497 and Avr3b^P7076. Bars represent standard errors from 2 independent replicates each.