Light intensity positively affects spontaneous silencing events in Nicotiana benthamiana. (A) Bars represent the frequency of spontaneous systemic silencing occurrence in plants (line 6.4) grown under HL and LL conditions. (B) Frequency of plants (line 6.4) that exhibited SSRS under HL and LL conditions. The leaf number is indicative of the growth stage at which silencing appeared. Leaf images at the top left represent the type of silencing monitored in each case. Asterisks (*) denote statistically significant difference. HL, high light intensity; LL, low light intensity; SSRS, spontaneous short-range silencing; nHL/LL, the total number of plants examined in each condition.