Mutations in Arabidopsis acyl‐CoA oxidase genes reveal distinct and overlapping roles in β‐oxidation

A. Raquel Adham, Bethany K. Zolman, Arthur Millius, Bonnie Bartel

Research output: Contribution to journalArticlepeer-review

Abstract

<div class="line" id="line-97"> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> Indole&hyphen;3&hyphen;butyric acid (IBA) is an endogenous auxin used to enhance rooting during propagation. To better understand the role of IBA, we isolated Arabidopsis&nbsp;IBA&hyphen;response ( </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ibr&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ) mutants that display enhanced root elongation on inhibitory IBA concentrations but maintain wild&hyphen;type responses to indole&hyphen;3&hyphen;acetic acid, the principle active auxin. A subset of&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ibr&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> mutants remains sensitive to the stimulatory effects of IBA on lateral root initiation. These mutants are not sucrose dependent during early seedling development, indicating that peroxisomal &beta;&hyphen;oxidation of seed storage fatty acids is occurring. We used positional cloning to determine that one mutant is defective in&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX1&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> and two are defective in&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX3&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> , two of the six Arabidopsis fatty acyl&hyphen;CoA oxidase ( </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ) genes. Characterization of T&hyphen;DNA insertion mutants defective in the other&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> genes revealed reduced IBA responses in a third gene,&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX4&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> . Activity assays demonstrated that mutants defective in&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX1&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ,&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX3&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> , or&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX4&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> have reduced fatty acyl&hyphen;CoA oxidase activity on specific substrates. Moreover,&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> acx1 acx2&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> double mutants display enhanced IBA resistance and are sucrose dependent during seedling development, whereas&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> acx1 acx3&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> and&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> acx1 acx5&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> double mutants display enhanced IBA resistance but remain sucrose independent. The inability of ACX1, ACX3, and ACX4 to fully compensate for one another in IBA&hyphen;mediated root elongation inhibition and the ability of ACX2 and ACX5 to contribute to IBA response suggests that IBA&hyphen;response defects in&nbsp; </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> acx&nbsp; </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> mutants may reflect indirect blocks in peroxisomal metabolism and IBA &beta;&hyphen;oxidation, rather than direct enzymatic activity of ACX isozymes on IBA&hyphen;CoA. </span></div>
Original languageAmerican English
JournalPlant Journal
Volume41
DOIs
StatePublished - Jan 26 2005
Externally publishedYes

Keywords

  • acyl-CoA oxidase
  • fatty acid catabolism
  • indole-3-butyric acid
  • peroxisome

Disciplines

  • Genetics
  • Biochemistry
  • Biology

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