Retracted: Nitric oxide enhances plant ultraviolet‐B protection up‐regulating gene expression of the phenylpropanoid biosynthetic pathway

Abstract

ABSTRACTThe link between ultraviolet (UV)‐B, nitric oxide (NO) and phenylpropanoid biosynthetic pathway (PPBP) was studied in maize and Arabidopsis. The transcription factor (TF) ZmP regulates PPBP in maize. A genetic approach using P‐rr (ZmP+) and P‐ww (ZmP‐) maize lines demonstrate that: (1) NO protects P‐rr leaves but not P‐ww from UV‐B‐induced reactive oxygen species (ROS) and cell damage; (2) NO increases flavonoid and anthocyanin content and prevents chlorophyll loss in P‐rr but not in P‐ww and (3) the NO scavenger 2‐(4‐carboxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide (cPTIO) blocks the UV‐B‐induced expression of ZmP and their targets CHS and CHI suggesting that NO plays a key role in the UV‐B‐regulated PPBP. Involvement of endogenous NO was studied in Arabidopsis nitric oxide dioxygenase (NOD) plants that express a NO dioxygenase gene under the control of a dexamethasone (DEX)‐inducible promoter. Expression of HY5 and MYB12, TFs involved in PPBP regulation, was induced by UV‐B, reduced by DEX in NOD plants and recovered by subsequent NO treatment. C4H regulates synapate esters synthesis and is UV‐B‐induced in a NO‐independent pathway. Data indicate that UV‐B perception increases NO concentration, which protects plant against UV‐B by two ways: (1) scavenging ROS; and (2) up‐regulating the expression of HY5, MYB12 and ZmP, resulting in the PPBP activation.