title: The Sweet Potato NAC-Domain Transcription Factor IbNAC1 Is Dynamically Coordinated by the Activator IbbHLH3 and the Repressor IbbHLH4 to Reprogram the Defense Mechanism against Wounding.
abstract: IbNAC1 is known to activate the defense system by reprogramming a genetic network against herbivory in sweet potato. This regulatory activity elevates plant defense potential but relatively weakens plants by IbNAC1-mediated JA response. The mechanism controlling IbNAC1 expression to balance plant vitality and survival remains unclear. In this study, a wound-responsive G-box cis-element in the IbNAC1 promoter from -1484 to -1479 bp was identified. From a screen of wound-activated transcriptomic data, one transcriptional activator, IbbHLH3, and one repressor, IbbHLH4, were selected that bind to and activate or repress, respectively, the G-box motif in the IbNAC1 promoter to modulate the IbNAC1-mediated response. In the early wound response, the IbbHLH3-IbbHLH3 protein complex binds to the G-box motif to activate IbNAC1 expression. Thus, an elegant defense network is activated against wounding stress. Until the late stages of wounding, IbbHLH4 interacts with IbbHLH3, and the IbbHLH3-IbbHLH4 heterodimer competes with the IbbHLH3-IbbHLH3 complex to bind the G-box and suppress IbNAC1 expression and timely terminates the defense network. Moreover, the JAZs and IbEIL1 proteins interact with IbbHLH3 to repress the transactivation function of IbbHLH3 in non-wounded condition, but their transcription is immediately inhibited upon early wounding. Our work provides a genetic model that accurately switches the regulatory mechanism of IbNAC1 expression to adjust wounding physiology and represents a delicate defense regulatory network in plants.
authors: Institute of Plant Biology, National Taiwan University, Taipei, Taiwan.
authors: Shi-Peng
authors: SP
authors: Chen
authors: Institute of Plant Biology, National Taiwan University, Taipei, Taiwan.
authors: Chih-Hsien
authors: CH
authors: Kuo
authors: Institute of Plant Biology, National Taiwan University, Taipei, Taiwan.
authors: Hsueh-Han
authors: HH
authors: Lu
authors: Institute of Plant Biology, National Taiwan University, Taipei, Taiwan.
authors: Hui-Shan
authors: HS
authors: Lo
authors: Institute of Plant Biology, National Taiwan University, Taipei, Taiwan.
authors: Kai-Wun
authors: KW
authors: Yeh
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000096:biosynthesis / Q000235:genetics*; D003517:Cyclopentanes / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D053263:Gene Regulatory Networks; D027723:Ipomoea batatas / Q000235:genetics* / Q000254:growth & development; D030821:Plants, Genetically Modified / Q000235:genetics; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D059467:Transcriptome / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D003517:Cyclopentanes; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C494589:EIL1 protein, Arabidopsis; C554741:JAZ1 protein, Arabidopsis; C418004:NAC1 protein, Arabidopsis; C000598790:bHLH30 protein, Arabidopsis