SEX-PHEROMONE COMPONENT RATIO IN THE CABBAGE-LOOPER MOTH ALTERED BY AMUTATION AFFECTING THE FATTY-ACID CHAIN-SHORTENING REACTIONS IN THE PHEROMONE BIOSYNTHETIC-PATHWAY
Ra. Jurenka et al., SEX-PHEROMONE COMPONENT RATIO IN THE CABBAGE-LOOPER MOTH ALTERED BY AMUTATION AFFECTING THE FATTY-ACID CHAIN-SHORTENING REACTIONS IN THE PHEROMONE BIOSYNTHETIC-PATHWAY, Insect biochemistry and molecular biology, 24(4), 1994, pp. 373-381
Comparisons in the sex pheromone biosynthetic pathway were made betwee
n a normal (wild type) and mutant strains of the cabbage looper moth,
Trichoplusia ni, maintained in laboratory colonies. The sex pheromone
of normal cabbage loopers consists of the major component, (Z-7-dodece
nyl acetate) and five minor compounds (all acetate esters) that are bi
osynthesized from fatty acid precursors by a combination of Delta 11 d
esaturation, chain shortening, reduction and acetylation. The mutant s
train is characterized by higher amounts of Z-9-tetradecenyl acetate a
nd lower amounts of Z-7-dodecenyl acetate. Amounts of fatty acid precu
rsor found in pheromone glands were determined and indicated that some
precursors were not chain shortened in the mutant strain. Amounts of
all 12 carbon fatty acids were lower in the mutant strain compared to
the normal strain. Incorporation studies using radiolabeled precursors
indicated that the Delta 11 desaturase, reductase and acetyl-CoA:fatt
y alcohol acetyltransferase were not affected by the mutation. However
, it appeared that chain-shortening steps in the biosynthetic pathway
were affected in the mutant strain. An in vitro chain-shortening assay
was developed using several different deuterium-labeled fatty acyl-Co
As as substrates to determine how the chain shortening reactions were
affected in the mutant strain. The amount of labeled product was deter
mined by gas chromatography-mass spectrometry. The normal strain prefe
rentially chain shortened Z-11-hexadecenoyl CoA by two rounds of beta-
oxidation to Z-7-dodecenoyl CoA. The mutant strain showed lower levels
of chain shortening and only one round of beta-oxidation occurred.