Abstract
A novel mutant of Arabidopsis (
Arabidopsis thaliana
), having highly glossy inflorescence stems, postgenital fusion in floral organs, and reduced fertility, was isolated from an ethyl methanesulfonate-mutagenized population and designated
glossyhead1
(
gsd1
). The
gsd1
locus was mapped to chromosome 1, and the causal gene was identified as a new allele of
Acetyl-Coenzyme A Carboxylase1
(
ACC1
), a gene encoding the main enzyme in cytosolic malonyl-coenzyme A synthesis. This, to our knowledge, is the first mutant allele of
ACC1
that does not cause lethality at the seed or early germination stage, allowing for the first time a detailed analysis of
ACC1
function in mature tissues. Broad lipid profiling of mature
gsd1
organs revealed a primary role for
ACC1
in the biosynthesis of the very-long-chain fatty acids (C
20:0
or longer) associated with cuticular waxes and triacylglycerols. Unexpectedly, transcriptome analysis revealed that
gsd1
has limited impact on any lipid metabolic networks but instead has a large effect on environmental stress-responsive pathways, especially senescence and ethylene synthesis determinants, indicating a possible role for the cytosolic malonyl-coenzyme A-derived lipids in stress response signaling.