Skip to main content
ARS Home » Research » Publications at this Location » Publication #68415
Title: METHODS FOR STUDIES OF AUXINS IN ARABIDOPSIS

Author
item ILIC, NEBOJSA - UNIVERSITY OF MARYLAND
item NORMANLY, JENNIFER - UNIV. OF MASSACHUSETTS
item Cohen, Jerry

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The plant hormone indole-3-acetic acid (IAA) is important in plant growth and in the development and ripening of fruits and vegetables. Previous methods for analysis had not been checked on cruciferous plants which include cabbage, kale, mustard, radish, broccoli and cauliflower. Using the wall cress plant as an example, we describe a new method for the accurate measurement of IAA in these difficult species of plants. The method also measures the levels of the related compound, indole-3-acetonitrile (IAN), which is found only in cruciferous plants. These studies will be useful to plant biologists interesed in hormone control of plant processes, to plant breeders interested in selection of elite varieties, and to molecular biologists interested in the characterization of plant hormone related genes and gene products.

Technical Abstract: The genetic advantages to the use of Arabidopsis mutants for the study of auxin metabolism have previously been partially offset by the complexity of indolic metabolism in this plant and by lack of proper methods. To address some of these problems we developed isotopic labeling methods to determine amounts and examine the metabolism of indolic compounds in Arabidopsis. Isolation and identification of endogenous indoleacetonitrile (IAN) [a possible precursor of the auxin indoleacetic acid (IAA)] was carried out under mild conditions, thus proving its natural occurrence. We describe here the synthesis of [13C1] labeled IAN and its utility in the GC-MS quantification of endogenous IAN levels. We also quantified the non enzymatic conversion of IAN to IAA under conditions used to hydrolyze IAA conjugates. [13C1] Labeled IAN was employed to assess the contribution of IAN to measured IAA following hydrolysis of IAA conjugates. We studied the estability and breakdown of the indolic glucosinolate glucobrassicin, which is known to be present in Arabidopsis. This is potentially an important concern when using Arabidopsis for studies of indolic biochemistry, since the levels of indolic auxins and auxin precursors are well below the levels of the indolic glucinosolates. We found that under conditions of extraction and base hydrolysis, formation of IAA from glucobrassicin was negligible.