Abstract
Alternative oxidase (AOX) is a mitochondrial protein encoded by the nuclear genome. In higher plants AOX genes form a small multigene family mostly consisting of the two subfamilies AOX1 and AOX2. Daucus carota L. is characterized by a unique extension pattern of AOX genes. Different from other plant species studied so far it contains two genes in both subfamilies. Therefore, carrot was recently highlighted as an important model in AOX stress research to understand the evolutionary importance of both AOX subfamilies. Here we report on the expression patterns of DcAOX1a, DcAOX1b and DcAOX2a and DcAOX2b. Our results demonstrate that all of the four carrot AOX genes are expressed. Differential expression was observed in organs, tissues and during de novo induction of secondary root phloem explants to growth and development. DcAOX1a and DcAOX2a indicated a differential transcript accumulation but a similar co-expression pattern. The genes of each carrot AOX sub-family revealed a differential regulation and responsiveness. DcAOX2a indicated high inducibility in contrast to DcAOX2b, which generally revealed low transcript abundance and rather weak responses. In search for within-gene sequence differences between both genes as a potential reason for the differential expression patterns, the structural organization of the two genes was compared. DcAOX2a and DcAOX2b showed high sequence similarity in their open reading frames (ORFs). However, length variability was observed in the N-terminal exon1 region. The predicted cleavage site of the mitochondrial targeting sequence in this locus is untypical small for both genes and consists of 35 amino acids for DcAOX2a and of 21 amino acids for DcAOX2b. The importance of structural gene organization and the relevancy of within-gene sequence variations are discussed. Our results strengthen the value of carrot as a model plant for future studies on the importance of AOX sub family evolution.
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Claims 10
Claim · model-written summary
All four carrot AOX genes are expressed.
- Taxon
- carrot
Daucus carotae0 - Gene
- AOX genese0
- Outcome
- expressede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“all of the four carrot AOX genes are expressed”
Claim · model-written summary
AOX expression differed across organs, tissues and induction of secondary root phloem explants.
- Taxon
- carrotDaucus carotat0
- Organ / stage
- secondary root phloem explantse0
- Outcome
- Differential expressione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Differential expression was observed in organs, tissues and during de novo induction of secondary root phloem explants to growth and development.”
t0“carrot”
Claim · model-written summary
DcAOX1a and DcAOX2a differed in transcript accumulation but shared a similar co-expression pattern.
- Taxon
- carrotDaucus carotat0
- Gene
- DcAOX1a and DcAOX2ae0
- Outcome
- differential transcript accumulatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“DcAOX1a and DcAOX2a indicated a differential transcript accumulation but a similar co-expression pattern.”
t0“carrot”
Claim · model-written summary
Genes within each carrot AOX subfamily differed in regulation and responsiveness.
- Taxon
- carrotDaucus carotae0
- Gene
- AOX sub-familye0
- Outcome
- differential regulation and responsivenesse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The genes of each carrot AOX sub-family revealed a differential regulation and responsiveness.”
Claim · model-written summary
DcAOX2a was highly inducible.
- Taxon
- carrotDaucus carotat0
- Gene
- DcAOX2ae0
- Outcome
- inducibilitye0
- Direction
- highe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“DcAOX2a indicated high inducibility”
t0“carrot”
Claim · model-written summary
DcAOX2b had low transcript abundance and weak responses.
- Taxon
- carrotDaucus carotat0
- Gene
- DcAOX2be0
- Outcome
- transcript abundance and rather weak responsese0
- Direction
- lowe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“DcAOX2b, which generally revealed low transcript abundance and rather weak responses.”
t0“carrot”
Claim · model-written summary
DcAOX2a and DcAOX2b open reading frames had high sequence similarity.
- Taxon
- carrotDaucus carotat0
- Gene
- DcAOX2a and DcAOX2be0
- Outcome
- sequence similarity in their open reading frames (ORFs)e0
- Direction
- highe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“DcAOX2a and DcAOX2b showed high sequence similarity in their open reading frames (ORFs).”
t0“carrot”
Claim · model-written summary
The N-terminal exon1 region varied in length.
- Taxon
- carrotDaucus carotat0
- Gene
- exon1e0
- Outcome
- length variabilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“length variability was observed in the N-terminal exon1 region”
t0“carrot”
Claim · model-written summary
The predicted targeting-sequence cleavage site was 35 amino acids for DcAOX2a.
- Taxon
- carrotDaucus carotat0
- Gene
- DcAOX2ae0
- Outcome
- amino acidse0
- Value
- 35 amino acidse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“consists of 35 amino acids for DcAOX2a and of 21 amino acids for DcAOX2b”
t0“carrot”
Claim · model-written summary
The predicted targeting-sequence cleavage site was 21 amino acids for DcAOX2b.
- Taxon
- carrotDaucus carotat0
- Gene
- DcAOX2be0
- Outcome
- amino acidse0
- Value
- 21 amino acidse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“consists of 35 amino acids for DcAOX2a and of 21 amino acids for DcAOX2b”
t0“carrot”