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‐3‐butyric acid (IBA) is an endogenous auxin used to enhance rooting during propagation. To better understand the role of IBA, we isolated Arabidopsis IBA‐response ( </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ibr </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‐type responses to indole‐3‐acetic acid, the principle active auxin. A subset of </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ibr </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 β‐oxidation of seed storage fatty acids is occurring. We used positional cloning to determine that one mutant is defective in </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX1 </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> and two are defective in </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX3 </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‐CoA oxidase ( </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ) genes. Characterization of T‐DNA insertion mutants defective in the other </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX </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, </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX4 </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 </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX1 </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> , </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX3 </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> , or </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> ACX4 </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> have reduced fatty acyl‐CoA oxidase activity on specific substrates. Moreover, </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> acx1 acx2 </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 </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> acx1 acx3 </i> <span style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> and </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> acx1 acx5 </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‐mediated root elongation inhibition and the ability of ACX2 and ACX5 to contribute to IBA response suggests that IBA‐response defects in </span> <i style='color: rgb(28, 29, 30); font-family: "Open Sans", icomoon, sans-serif; font-size: 16px;'> acx </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 β‐oxidation, rather than direct enzymatic activity of ACX isozymes on IBA‐CoA. </span></div>
Original language | American English |
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Journal | Plant Journal |
Volume | 41 |
DOIs | |
State | Published - Jan 26 2005 |
Externally published | Yes |
Keywords
- acyl-CoA oxidase
- fatty acid catabolism
- indole-3-butyric acid
- peroxisome
Disciplines
- Genetics
- Biochemistry
- Biology