title: Stress-induced co-expression of two alternative oxidase (VuAox1 and 2b) genes in Vigna unguiculata.
abstract: Cowpea (Vigna unguiculata) alternative oxidase is encoded by a small multigene family (Aox1, 2a and 2b) that is orthologous to the soybean Aox family. Like most of the identified Aox genes in plants, VuAox1 and VuAox2 consist of 4 exons interrupted by 3 introns. Alignment of the orthologous Aox genes revealed high identity of exons and intron variability, which is more prevalent in Aox1. In order to determine Aox gene expression in V. unguiculata, a steady-state analysis of transcripts involved in seed development (flowers, pods and dry seeds) and germination (soaked seeds) was performed and systemic co-expression of VuAox1 and VuAox2b was observed during germination. The analysis of Aox transcripts in leaves from seedlings under different stress conditions (cold, PEG, salicylate and H2O2 revealed stress-induced co-expression of both VuAox genes. Transcripts of VuAox2a and 2b were detected in all control seedlings, which was not the case for VuAox1 mRNA. Estimation of the primary transcript lengths of V. unguiculata and soybean Aox genes showed an intron length reduction for VuAox1 and 2b, suggesting that the two genes have converged in transcribed sequence length. Indeed, a bioinformatics analysis of VuAox1 and 2b promoters revealed a conserved region related to a cis-element that is responsive to oxidative stress. Taken together, the data provide evidence for co-expression of Aox1 and Aox2b in response to stress and also during the early phase of seed germination. The dual nature of VuAox2b expression (constitutive and induced) suggests that the constitutive Aox2b gene of V. unguiculata has acquired inducible regulatory elements.
authors.affiliation: Department of Biochemistry and Molecular Biology, Federal University of Ceara, 60455-760 Fortaleza, Ceará, Brazil.
authors.forename: José Hélio
authors.initials: JH
authors.lastname: Costa
authors.forename: Erika Freitas
authors.initials: EF
authors.lastname: Mota
authors.forename: Mariana Virginia
authors.initials: MV
authors.lastname: Cambursano
authors.forename: Martin Alexander
authors.initials: MA
authors.lastname: Lauxmann
authors.forename: Luciana Maia Nogueira
authors.initials: LM
authors.lastname: de Oliveira
authors.forename: Maria da Guia
authors.initials: Mda G
authors.lastname: Silva Lima
authors.forename: Elena Graciela
authors.initials: EG
authors.lastname: Orellano
authors.forename: Dirce
authors.initials: D
authors.lastname: Fernandes de Melo
mesh_terms: D000595:Amino Acid Sequence; D003080:Cold Temperature; D005091:Exons; D007887:Fabaceae / Q000201:enzymology* / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D018525:Germination; D006861:Hydrogen Peroxide; D007438:Introns; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011092:Polyethylene Glycols; D011401:Promoter Regions, Genetic; D012322:RNA Precursors; D012333:RNA, Messenger / Q000378:metabolism; D012639:Seeds / Q000201:enzymology; D012980:Sodium Salicylate; D013312:Stress, Physiological; D000099188:Alternative Oxidase
chemical_list: D006861:Hydrogen Peroxide; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D011092:Polyethylene Glycols; D012322:RNA Precursors; D012333:RNA, Messenger; D012980:Sodium Salicylate; D000099188:Alternative Oxidase