Stress-induced co-expression of two alternative oxidase (VuAox1 and 2b) genes in Vigna unguiculata.
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.
Costa
José Hélio
JH
Department of Biochemistry and Molecular Biology, Federal University of Ceara, 60455-760 Fortaleza, Ceará, Brazil.
Mota
Erika Freitas
EF
Cambursano
Mariana Virginia
MV
Lauxmann
Martin Alexander
MA
de Oliveira
Luciana Maia Nogueira
LM
Silva Lima
Maria da Guia
Mda G
Orellano
Elena Graciela
EG
Fernandes de Melo
Dirce
D
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
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