Fig. 7

A proposed molecular model for the regulation of Avr1b expression in the avirulent and virulent P. sojae strains. Both P. sojae strains P6497 and P7064 encodes Avr1b(+)and Avr1b(−) genes. In the virulent strain P6497 (the left panel), Avr1b(+)^P6497 and Avr1b(−)^P6497 are transcribed in a bidirectional manner and formed NATs during infection; the NATs are recognized by the putative endogenous cleavage machinery to produce Avr1b-asRNA^P6497. The produced sRNA targets on the newly transcribed Avr1b(+)^P6497 and generates abundant Avr1b-siRNA^P6497 that function as the RNA silencing signals, leading to abolished Avr1b(+)^P6497 function and escaped Rps1b recognition. In the avirulent strain P7064 (the right panel), a 10-bp deletion in Avr1b(−)^P7064 promoter region leads to significantly reduced Avr1b(−)^P7064 transcription and a failure of Avr1b(+)^P7064 silencing, allowing Avr1b(+)^P7064 be recognized by Rps1b