Broccoli long non-coding RNA BroNR8 affects salt tolerance by mediating AtWRKY54-related reactive oxygen species homeostasis in Arabidopsis.

Abstract

Main conclusion: BroNR8 regulates salt tolerance in Arabidopsis by upregulating AtWRKY54 and disrupting ROS homeostasis, revealing a key mechanism for salt sensitivity and offering insights for breeding salt-tolerant crops. Salt stress, which causes ion toxicity and oxidative damage in plants, severely threatens agricultural productivity and certain ecosystems. The regulatory network and mechanisms underlying plant responses to salt stress must be more thoroughly characterized. Many plant long non-coding RNAs (lncRNAs) transcribed by RNA polymerase II (Pol II) have been identified, with important roles in various physiological processes. The lncRNA BroNR8 may be a 270 nt long transcript transcribed by Pol III in broccoli. It is highly expressed in the root elongation zone of germinating seeds, and its accumulation is significantly increased by salt and abscisic acid (ABA) treatments. BroNR8 overexpression in Arabidopsis leads to a significant decrease in the tolerance of germinating seeds to salt stress in an ABA-independent manner. It also inhibits the maintenance of ROS homeostasis under saline conditions, thereby compromising the plant's capacity to scavenge endogenous H₂O₂. In response to salt stress, AtWRKY54 expression in BroNR8-AtOX increased significantly. Moreover, germinating seeds of wrky54 were highly tolerant to salt and H₂O₂. Furthermore, antioxidant enzyme activities in wrky54 increased significantly, while the ROS content decreased significantly. These results suggest that BroNR8 may affect Arabidopsis tolerance to salt stress by regulating AtWRKY54-mediated ROS homeostasis. The BroNR8/AtWRKY54/ROS module detected in this study may help to clarify the molecular network regulating plant salt stress responses mediated by ncRNAs. The study findings may provide breeders with new gene resources for developing stress-resistant varieties.