A positive feedback regulatory loop, SA-AtNAP-SAG202/SARD1-ICS1-SA, in SA biosynthesis involved in leaf senescence but not defense response

Abstract Salicylic acid (SA) is an important plant hormone that regulates defense responses and leaf senescence. It imperative to understand upstream factors regulate genes of SA biosynthesis. SAG202/SARD1 a key regulator for isochorismate synthase 1 ( ICS1 ) induction biosynthesis in responses. The regulatory mechanism during senescence not well understood. Here we show AtNAP, senescence-specific NAC family transcription factor, directly senescence-associated gene named SAG202 as revealed yeast one-hybrid planta assays. Inducible overexpreesion AtNAP lead high levels precocious leaves. Individual knockout mutants sag202 ics1 have markedly reduced display significantly delayed phenotype. Furthermore, positively feedback . Our research has uncovered unique positive loop, SA- - -SA, operates control associated with but response.