| Abstract Detail
Hormone Biology Zhao, Yingchun [1], Hasenstein, Karl [2]. TFIBA counteracts auxin function in flax. TFIBA (4,4,4-trifluoro-3-(indole-3-)butyric acid), PCIB (p-chloro-phenoxy-isobutyric acid) and STS (silver thiosulfate) all promote elongation of primary roots, diminish root diameter and inhibit root hair growth despite increasing the content of endogenous free IAA. The function of TFIBA can be completely reversed by IAA. TFIBA inhibits auxin-transport (both acropetal and basipetal) in the root at supra-optimal concentrations (>300 µM), but auxin transport was not affected by PCIB or STS. TFIBA and PCIB decreased ACC (aminocyclopropane-1-carboxylic acid) content in the root to less than one half of control, and reduced ethylene production of flax seedlings. In contrast, STS increased ACC content in the root, and ethylene production of seedlings. TFIBA and PCIB also reduced ethylene induction by IAA or ACC in hypocotyls. The ACC content in hypocotyls corresponded with ethylene production. The data suggest that PCIB and TFIBA counteract IAA by suppressing ACC formation while STS inhibits ethylene action. To examine if ACC synthase (ACS) or oxidase (ACO) is the target of these compounds, degenerate primers were used to amplify the ACS and ACO fragments in flax roots. Based upon cloned and sequenced fragments, 14 isoforms of ACS and 3 isoforms of ACO were identified. Real time PCR results show that, after 24 hrs of treatment, the expression of ACO isoforms was not changed by TFIBA, PCIB or STS. However, two ACS isoforms were down-regulated by TFIBA and PCIB. Further study will identify more responsive isoforms of ACS and ACO to IAA, TFIBA, PCIB, and STS. Supported by NASA grant NNA04CK48G.
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1 - Univ of Louisiana at Lafayette, Biology, P.O. Box 42451, Lafayette, LA, 70504, U.S.A.
2 - Univ of Louisiana at Lafayette, Biology
Keywords:
TFIBA
PCIB
anti-auxin
ethylene
root growth.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P35028
Abstract ID:875 |
