Promoter trapping of a novel medium-chain acyl-CoA oxidase, which is induced transcriptionally during Arabidopsis seed germination.
The first step of peroxisomal fatty acid beta-oxidation is catalyzed by a family of acyl-CoA oxidase isozymes with distinct fatty acyl-CoA chain-length specificities. Here we identify a new acyl-CoA oxidase gene from Arabidopsis (AtACX3) following the isolation of a promoter-trapped mutant in which beta-glucuronidase expression was initially detected in the root meristem. In acx3 mutant seedlings medium-chain acyl-CoA oxidase activity was reduced by 95%, whereas long- and short-chain activities were unchanged. Despite this reduction in activity lipid catabolism and seedling development were not perturbed. AtACX3 was cloned and expressed in Escherichia coli. The recombinant enzyme displayed medium-chain acyl-CoA substrate specificity. Analysis of beta-glucuronidase activity in acx3 revealed that, in addition to constitutive expression in the root axis, AtACX3 is also up-regulated strongly in the hypocotyl and cotyledons of germinating seedlings. This suggests that beta-oxidation is regulated predominantly at the level of transcription in germinating oilseeds. After the discovery of AtACX3, the Arabidopsis acyl-CoA oxidase gene family now comprises four isozymes with substrate specificities that encompass the full range of acyl-CoA chain lengths that exist in vivo.
Centre for Novel Agricultural Products, Department of Biology, University of York, York, YO10 5YW, United Kingdom.
P J
PJ
Eastmond
M A
MA
Hooks
D
D
Williams
P
P
Lange
N
N
Bechtold
C
C
Sarrobert
L
L
Nussaume
I A
IA
Graham
D042962:Acyl-CoA Oxidase; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000196:embryology / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005786:Gene Expression Regulation; D018525:Germination; D008969:Molecular Sequence Data; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds; D013379:Substrate Specificity; D014158:Transcription, Genetic
D029681:Arabidopsis Proteins; D018076:DNA, Complementary; D011994:Recombinant Proteins; D010088:Oxidoreductases; C467988:ACX3 protein, Arabidopsis; D042962:Acyl-CoA Oxidase