Program of the 2001 International Worm Meeting - Sternberg Lab ...

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333. Identification of two novel clk
mutants
Chang-Su Lim, Kang-Ja Lee, Judith
Campisi
Lawrence Berkeley National Laboratory,
Berkeley, CA 94720
It has previously been shown that mutations in
the genes clk-1, clk-2, clk-3, and gro-1 are
highly pleiotropic, causing an increase in the
average period of nematode development, a
slowing of rhythmic behaviors such as
defecation, swimming, and pharyngeal
pumping, and a lengthening of life span.
Intuitively these genes may be positioned in the
same genetic pathway because mutations in any
one of them give rise to similar mutant
phenotypes. However, it remains possible that
they might also function independently of each
other. We are particularly interested in the life
span extension conferred by clk mutants.
To begin to understand how clk genes function
in life span regulation, we performed five
independent EMS mutagenesis experiments,
screening 20, 000 mutagenized genomes in
total. We identified two novel clk mutants. Both
mutants complement each other, or the four
known clk mutants, clk-1, clk-2, clk-3, and
gro-1.
Currently, we are characterizing the phenotypes
of the clk-4 and clk-5 mutants.
334. Developmental control of
coenzyme Q levels - the L2 arrest in
clk-1 mutants coincides with an
increased reliance on respiratory
energy metabolism
Tanya Jonassen, Pamela L. Larsen,
Kym Faull, Catherine F. Clarke
Department of Chemistry and Biochemistry,
University of California, Los Angeles
334
The developmental and long-lived phenotypes
described for the C. elegans clk-1 mutants
depend critically upon a dietary source of
coenzyme Q. Coenzyme Q functions in cells as
an essential redox-active component of both
mitochondrial and plasma membrane electron
transport, as an essential lipid antioxidant, and
plays a role in uridine synthesis and uncoupling
activity in mitochondria. When provided a diet
lacking coenzyme Q, the clk-1 mutants display a
growth arrest in early development from eggs,
and sterility upon emerging from dauer larvae.
As observed for the corresponding yeast coq7
mutants, the clk-1 mutants have a defect in
coenzyme Q biosynthesis. Following growth on
Q 8 -replete E. coli, the standard diet for C.
elegans, the clk-1 mutants completely lack Q 9
and accumulate the biosynthetic intermediate
demethoxy-Q 9 . The subscripts 8 and 9 refer to
the number of isoprene units in the tail of Q
synthesized by E. coli and C. elegans,
respectively. The clk-1 mutants display the early
developmental arrest when fed any of three
distinct Q-less E.coli strains, including ubiA - ,
ubiE - , or ubiG - mutants. These results indicate
that the clk-1 arrest phenotype results from the
lack of Q and not from the distinct
Q-intermediates that accumulate in these Q-less
E. coli strains.
Slow growing C. elegans mutants that map to
genetic loci other than clk-1, were evaluated for
Q biosynthesis. This was of particular interest
due to the overlap of the physical map position
of the homologs of the yeast genes COQ2 and
COQ5 with the genetic interval containing
clk-2. We find that clk-2, clk-3, and mev-1
produce coenzyme Q, as detected by
HPLC/ECD assays. We find that clk-2, clk-3,
gro-1 and gro-2 all grow to adulthood on a diet
of Q-less E. coli. The very slow developing and
long-lived double mutant daf-2 clk-1 is