26
G. Jansen et al.
2.2.4 Several Ga Genes Are Involved in Perception
The expression of 14 of the 16 new Ga genes in amphid neurons or
other putative sensory neurons, suggests they might be involved in
perception, or in the development of sensory neurons, as has been
reported for ODR-3 (Roayaie et al. 1998) and GPA-3 (Zwaal et al.
1997).
We tested whether the endings of the amphid and phasmid neurons
are still exposed to the environment by dye filling (Perkins et al.1986).
None of the mutants tested, except gpa-3QL animals (Zwaal et al.
1997), showed reduced dye filling (data not shown). Surprisingly, gpalOXS animals showed stronger dye filling (data not shown). This phenotype may be the result of structural changes in the sheath cells.
The ability of the mutants to sense and respond to several water
soluble or volatile stimuli was tested: chemotaxis to sodium acetate
(NaAc), NaCI and glucose (Ward 1973), avoidance of coppersulfate,
sodium dodecylsulfate (SDS) and 4 M fructose (osmotic avoidance;
Culotti and Russell 1978; Bargmann and Mori 1997), and attraction to,
or aversion of, several different volatile compounds (Bargmann et al.
1993; Sengupta et al. 1994; Troemel et al. 1997). Furthermore, male
potency was tested (Mendel et al. 1995). Surprisingly, we found only
few phenotypes for loss-of-function alleles. Three genes seem involved
in chemotaxis to water soluble compounds: gpa-3, gpa-6, and odr-3
(Table 2; Fig. 5A,B). Three loss-of-function mutations affect avoidance
behavior: gpa-3, gpa-7, and odr-3 (Roayaie et al. 1998) (Table 2;
Fig. 5C). Also, three genes seem to be involved in olfaction: gpa-2
(Roayaie et al. 1998), gpa-5, and odr-3 (Roayaie et al. 1998) (Table 2;
Fig. 5D). None of the loss-of-function alleles showed reduced male
potency.
In contrast, eight of the ten gain-of-function alleles tested showed
phenotypes in these assays (Table 2). Although we cannot extrapolate
gene function from dominant mutants with any certainty, these phenotypes can provide hints about the involvement of G proteins in specific
cellular functions. They show that there are probably independent cells
and pathways for acetate/CI and glucose perception (Table 2). The ASI
neurons would be likely candidates for the perception of NaAc and
NaCI, the ADF and ASH neurons would be likely, but not perfect,
candidates for glucose perception. Furthermore, there are probably inde-
G. Jansen et al.
2.2.4 Several Ga Genes Are Involved in Perception
The expression of 14 of the 16 new Ga genes in amphid neurons or
other putative sensory neurons, suggests they might be involved in
perception, or in the development of sensory neurons, as has been
reported for ODR-3 (Roayaie et al. 1998) and GPA-3 (Zwaal et al.
1997).
We tested whether the endings of the amphid and phasmid neurons
are still exposed to the environment by dye filling (Perkins et al.1986).
None of the mutants tested, except gpa-3QL animals (Zwaal et al.
1997), showed reduced dye filling (data not shown). Surprisingly, gpalOXS animals showed stronger dye filling (data not shown). This phenotype may be the result of structural changes in the sheath cells.
The ability of the mutants to sense and respond to several water
soluble or volatile stimuli was tested: chemotaxis to sodium acetate
(NaAc), NaCI and glucose (Ward 1973), avoidance of coppersulfate,
sodium dodecylsulfate (SDS) and 4 M fructose (osmotic avoidance;
Culotti and Russell 1978; Bargmann and Mori 1997), and attraction to,
or aversion of, several different volatile compounds (Bargmann et al.
1993; Sengupta et al. 1994; Troemel et al. 1997). Furthermore, male
potency was tested (Mendel et al. 1995). Surprisingly, we found only
few phenotypes for loss-of-function alleles. Three genes seem involved
in chemotaxis to water soluble compounds: gpa-3, gpa-6, and odr-3
(Table 2; Fig. 5A,B). Three loss-of-function mutations affect avoidance
behavior: gpa-3, gpa-7, and odr-3 (Roayaie et al. 1998) (Table 2;
Fig. 5C). Also, three genes seem to be involved in olfaction: gpa-2
(Roayaie et al. 1998), gpa-5, and odr-3 (Roayaie et al. 1998) (Table 2;
Fig. 5D). None of the loss-of-function alleles showed reduced male
potency.
In contrast, eight of the ten gain-of-function alleles tested showed
phenotypes in these assays (Table 2). Although we cannot extrapolate
gene function from dominant mutants with any certainty, these phenotypes can provide hints about the involvement of G proteins in specific
cellular functions. They show that there are probably independent cells
and pathways for acetate/CI and glucose perception (Table 2). The ASI
neurons would be likely candidates for the perception of NaAc and
NaCI, the ADF and ASH neurons would be likely, but not perfect,
candidates for glucose perception. Furthermore, there are probably inde-