Haloxyfop mode of action in liquid cultures of proso millet: An analysis of haloxyfop sensitivity changes during growth
Haloxyfop is a grass-selective herbicide that inhibits acetyl-CoA carboxylase in species that are not tolerant to the herbicide. Liquid cultures of proso millet (Panicum miliaceum) cells treated with haloxyfop at different phases of growth exhibited different levels of sensitivity to the herbicide. Treatment of 1-d cultures with 1 {mu}M haloxyfop completely inhibited growth within 48 h. In contrast, 1 mM haloxyfop was required to elicit a similar response in 4-, 7-, or 10-d cultures. Calculated IC{sub 50} values indicated a 300-fold decrease in haloxyfop sensitivity during the period from 1 to 4 d. This period of growth coincided with the greatest increase in cell number during culture growth and suggested that dividing cells are most sensitive to haloxyfop. Uptake and metabolism of {sup 14}C-haloxyfop in 1-d and 4-d cultures were compared. In both cultures, amounts of radiolabel uptake were similar. Almost all radioactivity extracted from 1- and 4-d cells was present as the parent compound. These results suggested that the sensitivity change was related to other factors. Acetyl-CoA carboxylase activity of proso millet cells, measured in vitro by the acetyl-CoA-dependent incorporation of {sup 14} C-bicarbonate into an acid-stable product, was essentially constant during culture growth. Micromolar concentrations of haloxyfop significantly inhibited acetyl-CoA carboxylase activity from both sensitive and insensitive cultures. Thus, the change in the sensitivity of cultures to haloxyfop was not correlated with changes in acetyl-CoA carboxylase abundance, activity, or sensitivity to haloxyfop during culture growth. In vivo incorporation of {sup 14}C-acetate into lipids was decreased by 1 {mu}M haloxyfop in both 1-d and 4-d cultures at the earliest sampling times but the amount of inhibition was significantly greater in the sensitive cultures.
- Research Organization:
- Purdue Univ., Indianapolis, IN (United States)
- OSTI ID:
- 5475493
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CARBOXYLASE
ENZYME ACTIVITY
HERBICIDES
METABOLISM
MILLET
SENSITIVITY
CARBON 14 COMPOUNDS
CELL CYCLE
GRAIN GROWTH
TRACER TECHNIQUES
CARBON COMPOUNDS
CARBON-CARBON LYASES
CARBOXY-LYASES
CEREALS
ENZYMES
GRAMINEAE
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LILIOPSIDA
LYASES
MAGNOLIOPHYTA
PESTICIDES
PLANTS
550501* - Metabolism- Tracer Techniques