title: Exposure to various abscission-promoting treatments suggests substantial ERF subfamily transcription factors involvement in the regulation of cassava leaf abscission.
abstract: Cassava plants (Manihot esculenta Crantz) have obvious abscission zone (AZ) structures in their leaf pulvinus-petioles. Cassava leaf abscission can be triggered by either 17 days of water-deficit stress or 4 days of ethylene treatment. To date, little is known about cassava AP2/ERF factors, and less is known regarding their roles in regulating abscission zone development.
  
  
  
  Here, the cassava and Arabidopsis AP2/ERF genes were compared, finding that the cassava genome contains approximately 1.54-fold more ERF subfamily than the Arabidopsis genome. Microarray analysis was used to identify the AP2/ERF genes that are expressed in cassava leaf pulvinus-petiole abscission zones by comparing the AP2/ERF gene expression profiles of ethylene- and water-deficit stress-induced leaf abscission. In total, 99 AP2/ERF genes were identified as expressed in AZs across six time points during both ethylene- and water-deficit stress-induced leaf abscission. Comparative expression profile analysis of similar SOTA (Self Organizing Tree Algorithm) clusters at six time points during ethylene- and water-deficit stress-induced leaf abscission demonstrated that 20 ERF subfamily genes had similar expression patterns in response to both treatments. GO (Gene Ontology) annotation confirmed that all 20 ERF subfamily genes participate in ethylene-mediated signalling. Analysis of the putative ERF promoter regions shown that the genes contained primarily ethylene- and stress-related cis-elements. Further analysis of ACC oxidase activity in AZs across six time points during abscission shown increased ethylene production in response to both ethylene and water-deficit stress; however, the difference was more dramatic for water-deficit stress. Finally, the expression ratios of 20 ERF subfamily genes were analysed in two cassava cultivars, 'KU50' and 'SC5', that exhibit different levels of leaf abscission when challenged with the same water-deficit stress. The analysis indicated that most of the ERF genes were expressed at higher levels in the precocious abscission 'KU50' cultivar than in the delayed abscission 'SC5' cultivar.
  
  
  
  Ccomparative analysis of both ethylene- and water-deficit stress-induced leaf abscission shown that the ERF subfamily functions in the regulation of cassava abscission zone development.
authors.affiliation: Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China. liaowenbin@itbb.org.cn.
authors.forename: Wenbin
authors.initials: W
authors.lastname: Liao
authors.affiliation: Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China.
authors.forename: Yayun
authors.initials: Y
authors.lastname: Li
authors.affiliation: Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China.
authors.forename: Yiling
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China.
authors.forename: Gan
authors.initials: G
authors.lastname: Wang
authors.affiliation: Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, China. mingpengcatas@gmail.com.
authors.forename: Ming
authors.initials: M
authors.lastname: Peng
mesh_terms: D000465:Algorithms; D020869:Gene Expression Profiling / Q000379:methods*; D018506:Gene Expression Regulation, Plant; D063990:Gene Ontology; D002365:Manihot / Q000235:genetics / Q000254:growth & development*; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D010940:Plant Proteins; D014157:Transcription Factors
keywords: AP2/ERF; Cassava abscission zone; Ethylene; Water-deficit stress