A Novel NAC-Type Transcription Factor, NAC87, from Oilseed Rape Modulates Reactive Oxygen Species Accumulation and Cell Death

Abstract

Reactive oxygen species (ROS) are thought to play a dual role in plants by functioning as signaling molecules and toxic by-products 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 ROS and cell death accompanied by typical changes at the morphological and cellular levels. The 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 mobility 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 that oilseed rape NAC87 is a novel NAC transcription factor that acts as a positive regulator of ROS metabolism and cell death.

Genetic Network between Leaf Senescence and Plant Immunity: Crucial Regulatory Nodes and New Insights

“…Similarly, NAC087/046 control dPCD by regulating BFN1 in Arabidopsis lateral root cap [47]. Furthermore, BnaNAC87, the homolog of NAC087 in Brassica napus, acts as a positive regulator of ROS metabolism and cell death [48] and it binds the promoter of HIN1 [32,48]. However, the function of NAC087/046 in plant immunity remains unknown.…”

Engineering Multiple Abiotic Stress Tolerance in Canola, Brassica napus

“…BnNAC19 and BnNAC82 have been shown to induce a hypersensitive response and cell death under stress due to ROS accumulation (Wang B. et al, 2015). Independent studies have reported similar observations in tobacco and B. napus protoplasts due to transient expression of BnNAC55, BnNAC56, BnNAC87, and BnNAC103 (Niu et al, 2014;Niu et al, 2016;Chen et al, 2017;Yan et al, 2017). Contrary to this transgenic rice overexpressing SNAC3 showed enhanced tolerance to high temperature, drought, and oxidative stress caused by methyl viologen (MV) due to lower accumulation of ROS (Fang et al, 2015).…”

May the Fittest Protein Evolve: Favoring the Plant‐Specific Origin and Expansion of NAC Transcription Factors

“…Bl/BLOOD (Prunus persica) Full length and C-terminal -Regulates anthocyanin pigmentation [105] 10 BnaNAC87 (Brassica napus) Full length Nucleus Positively regulates reactive oxygen species metabolism and cell death [121] 11 BnNAC55 (Brassica napus) Full length Nucleus Modulates reactive oxygen species accumulation and cell death [122] 12 BnNAC2 (Brassica napus) Full length -Involved in response to high salinity stress [123] 13 CaNAC1 (Capsicum annuum) Full length and C-terminal Nucleus Regulates defense reponses against pathogens [124] 14 CarNAC3 (Cicer arietinum) Full length and C-terminal Nucleus Involved in drought stress response and developmental processes [125] 15 CarNAC4 (Cicer arietinum) Full length and C-terminal Nucleus Enhances drought and salt stress tolerance [13] 16 CpNAC2 (Carica papaya) Full length Nucleus Activates carotenoid biosynthesis related genes and involved in fruit ripening [126] 17 DlNAC1 (Dendranthema lavandulifolium)…”