A Novel NAC-type Transcription Factor, NAC87, from Oilseed Rape Modulates Reactive Oxygen Species Accumulation and Cell Death
Jingli Yan, Tiantian Tong, Xin Li, Qinqin Chen, Moyu Dai, Fangfang Niu, Mingfeng Yang, Michael K. Deyholos, Bo Yang, Yuan-Qing Jiang.
Plant and Cell Physiology
DOI: 10.1093/pcp/pcx184
Abstract: Reactive oxygen species (ROS) are thought to play a dual role in plants by functioning as signaling molecules and toxic byproducts of aerobic metabolism. The hypersensitive response (HR) is a typical feature of immune responses in plants and also a type of programmed cell death (PCD). How these two processes are regulated in oilseed rape (Brassica napus L.) at the transcriptional level remains largely unknown. In this study, we report that an oilseed rape (Brassica napus L.) NAM-ATAF-CUC (NAC)-type transcription factor NAC87 modulates reactive oxygen species (ROS) and cell death accompanied by typical changes at the morphological and cellular levels. BnaNAC87 gene was induced by multiple stress and hormone treatments and was highly expressed in senescent leaves by quantitative reverse transcription PCR (qRT-PCR). BnaNAC87 is located in nuclei and has transcriptional activation activity. Expression of BnaNAC87 promoted significant ROS production, cell death as well as death of protoplasts, as indicated by histological staining. In addition, putative downstream target genes of NAC87 were identified through both qRT-PCR and dual luciferase reporter assays. We found that genes implicated in ROS generation (RbohB), cell death (VPE1a, ZEN1), leaf senescence (WRKY6, ZAT12) and defense (PR2, PR5 and HIN1) were significantly induced. Through an electrophoretic motility shift assay (EMSA), we confirmed that BnaNAC87 directly binds to the NACRS-containing promoter fragments of ZEN1, ZAT12, HIN1 and PR5 genes. From these results, we conclude oilseed rape NAC87 is a novel NAC transcription factor that acts as a positive regulator of ROS metabolism and cell death.