Transcriptional regulation of the immune receptor FLS2 controls the ontogeny of plant innate immunity (Plant Cell)

FLS2 is a well-known cell-surface receptor that triggers plant immune response. Zou et al. asked whether its expression level is age-dependent, and found that FLS2 is expressed at very low levels in newly-emerged seedlings. They identified two closely related transcription factors TOE1 and TOE2 that negatively regulate FLS2 expression and FLS2-mediated immunity in very young seedlings. Previous studies identified TOE1/2 as targets of miR172. The authors showed that as plants age, increasing levels of miR172 gradually suppress the inhibitory effects of TOE1/2, enabling FLS2 expression. Interestingly, flg22 (which mimics pathogen proteins) also increases miR172 levels, promoting expression of FLS2. The authors note that this, along with miR172’s well-known role in promoting flowering, could coordinate plant growth, immunity and flowering time. (Summary by Mary Williams) Plant Cell 10.1105/tpc.18.00297