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  • Sex ratio  (5)
  • Acetolactate synthase  (4)
  • Springer  (9)
  • American Chemical Society (ACS)
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  • Springer  (9)
  • American Chemical Society (ACS)
  • Elsevier  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Effect of four classes of herbicides on growth and acetolactate-synthase activity in several variants of Arabidopsis thaliana (1992)
    Springer
    Planta 188 (1992), S. 491-497 
    Details
    ISSN: 1432-2048
    Keywords: Acetolactate synthase ; Arabidopsis (mutants) ; Herbicide resistance ; Mutant (herbicide resistance)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated a triazolopyrimidine-resistant mutant csrl-2, of Arabidopsis thaliana (L.) Heynh. Here, we compare csrl-2 with the previously isolated mutants csrl and csr1-1, and with wild-type Arabidopsis for responses to members of four classes of herbicides, namely, sulfonylureas, triazolopyrimidines, imidazolinones, and pyrimidyl-oxy-benzoates. Two separable herbicide binding sites have been identified previously on the protein of acetolactate synthase (ALS). Here, the mutation giving rise to csrl, originating in a coding sequence towards the 5′ end of the ALS gene, and that in csrl-2, affected the inhibitory action on growth and ALS activity of sulfonylurea and triazolopyrimidine herbicides but not that of the imidazolinones or pyrimidyl-oxybenzoates. The other mutation, in csrl-1, originating in a coding sequence towards the 3′ end of the ALS gene, affected the inhibitory action of imidazolinones and pyrimidyl-oxy-benzoates but not that of the sulfonylureas or triazolopyrimidines. Additional, stimulatory effects of some of these herbicides on growth of seedlings was unrelated to their effect on their primary target, ALS. The conclusion from these observations is that one of the two previously identified herbicide-binding sites may bind sulfonylureas and triazolopyrimidines while the other may bind imidazolinones and pyrimidyl-oxy-benzoates within a herbicide-binding domain on the ALS enzyme. Such a comparative study using near-isogenic mutants from the same species allows not only the further definition of the domain of herbicide binding on ALS but also could aid investigation of the relationship between herbicide-, substrate-, and allosteric-binding sites on this enzyme. This research was supported by an Operating Grant from the Natural Sciences and Engineering Research Council of Canada to J.K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197040
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  • 2
    Electronic Resource
    Electronic Resource
    Host-size-dependent sex ratios among parasitoid wasps: does host growth matter? (1989)
    Springer
    Oecologia 78 (1989), S. 420-426 
    Details
    ISSN: 1432-1939
    Keywords: Sex ratio ; Parasitoid wasps ; Host size
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Waage's (1982) hypothesis that host-size-dependent sex ratios will occur in parasitoids of nongrowing hosts and not in parasitoids of growing hosts is examined using published data on parasitoid wasps. Waage's hypothesis is supported as a general, but not absolute, rule: among solitary parasitoid wasps, a significantly greater proportion of parasitoids of nongrowing than of growing hosts show some evidence of host-size-dependent sex ratios (85% versus 42%, G=6.54, P〈 0.05). The premise of Waage's hypothesis-that for parasitoids which develop in a growing stage, host size at oviposition is not a good predictor of the amount of resources available to the developing parasitoid-is also examined. It is suggested that across host species Waage's premise will hold for some, but not all, parasitoids of growing hosts. Likely exceptions to Waage's premise, and thus his prediction, are discussed. Parasitoids of growing hosts which are expected to have evolved hostsize-dependent sex ratios include parasitoids which utilize a narrow size range of host species, parasitoids which can distinguish among host species by some criterion other than size, and parasitoids which utilize host species whose susceptible instars do not overlap in size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379119
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  • 3
    Electronic Resource
    Electronic Resource
    Sex ratio response of the parasitoid wasp Muscidifurax raptor to other females (1993)
    Springer
    Oecologia 94 (1993), S. 428-433 
    Details
    ISSN: 1432-1939
    Keywords: Sex ratio ; Parasitoid wasps ; Local mate ; competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study examines the sex ratio response of the parasitoid wasp Muscidifurax raptor to conspecific and confamilial females in relation to two groups of functional sex ratio models, local mate competition and host quality models. In some but not all experiments, M. raptor females produced a greater proportion of sons in the presence of a conspecific female than when alone, and this sex ratio effect carried over for a day after the females were isolated from each other M. raptor females also produced a greater proportion of sons in the presence of a female of the confamilial parasitoid Spalangia cameroni than when alone (although only on the second day of exposure to S. cameroni, not on the first). M. raptor's sex ratio increase in the presence of conspecifics is consistent with local mate competition models but not with host quality models because the presence of a conspecific female did not cause there to be more, and thus potentially smaller, offspring developing per host. In contrast, the presence of a S. cameroni female did cause there to be more offspring developing per host than when a M. raptor female was alone; thus M. raptor's sex ratio increase in the presence of S. cameroni may be explained by host quality models. An alternative explanation for the sex ratio increase in response to confamilials is that only a sex ratio response to conspecifics may be adaptive, due to local mate competition; but M. raptor females may be unable to distinguish between conspecific and S. cameroni females.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317119
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  • 4
    Electronic Resource
    Electronic Resource
    A double mutant allele, csr1-4, of Arabidopsis thaliana encodes an acetolactate synthase with altered kinetics (1995)
    Springer
    Planta 196 (1995), S. 64-68 
    Details
    ISSN: 1432-2048
    Keywords: Acetolactate synthase ; Arabidopsis ; Enzyme kinetics ; Herbicide resistance ; Mutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A comparison is made of the kinetic characteristics of acetolactate synthase (EC 4.1.3.18) in extracts from Columbia wild type and four near-isogenic, herbicide-resistant mutants of Arobidopsis thaliana (L.) Heynh. The mutants used were the chlorsulfuron-resistant GH50 (csr1-1), the imazapyr-resistant GH90 (csr1-2), the triazolopyrimidine-resistant Tzp5 (csr1-3) and the multiherbicide-resistant, double mutant GM4.8 (csr1-4), derived from csr1-1 and csr1-2 by intragenic recombination (G. Mourad et al. 1994, Mol. Gen. Genet. 243, 178–184). $$K_{m_{app} } $$ and V max values for the substrate pyruvate were unaffected by any of the mutations giving rise to herbicide resistance. Feedback inhibition by L-valine (L-Val), L-leucine (L-Leu) and L-isoleucine (L-Ile) of acetolactate synthase extracted from wild type and mutants fitted a mixed competitive pattern most closely. Ki values for L-Val, L-Leu and L-Ile inhibition were not significantly different from wild type in extracts from csr1-1, csr1-2, and csr1-3. K i values were significantly higher than wild type by two- and five-fold, respectively, for csr1-4 with L-Val and L-Leu but not L-Ile. GM4.8 (csr1-4) plants were also highly resistant in their growth to added L-Val and L-Leu. The data suggest that (i) single mutational changes occurred that affected the binding of herbicides to the acetolactate synthase molecule without influencing the binding of substrates and feedback inhibitors (e.g. csr1-1, csr1-2 and csr1-3) and (ii) bringing two of these single mutations (csr1-1 and csr1-2) together in a double mutant (csr1-4) gave rise to an enzyme with altered characteristics as well as plants with changed growth in response to added L-Val and L-Leu. The implications of these conclusions for genetic transformation using these herbicide-resistant genes are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193218
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  • 5
    Electronic Resource
    Electronic Resource
    A valine-resistant mutant ofArabidopsis thaliana displays an acetolactate synthase with altered feedback control (1994)
    Springer
    Planta 192 (1994), S. 249-255 
    Details
    ISSN: 1432-2048
    Keywords: Acetolactate synthase ; Amino acid (branched chain) ; Arabidopsis ; Feedback regulation ; Mutant ; Valine resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A valine-resistant mutant line, VAL-2, ofArabidopsis thaliana (L.) Heynh. was identified by screening M 2 populations of ethylmethane-sulfonate-mutagenized seeds. The resistance was found to be due to a single, dominant, nuclear gene mutation. Assay of acetolactate synthase (ALS) indicated that the valine resistance in this mutant is caused by decreased sensitivity of ALS to the branched-chain amino acids, valine, leucine andisoleucine. A two fold decrease in apparentK m value for pyruvate of the mutant ALS enzyme was detected compared with that of the wild type. The sensitivity of the ALS enzyme to sulfonylurea, imidazolinone and triazolopyrimidine herbicides was not altered in the mutant. At the plant growth level the mutant was also resistant to valine plus leucine, but was sensitive to leucine orisoleucine alone. The mutant gene,var1, maps, or is very closely linked, toCSR1, the gene encoding acetolactate synthase inArabidopsis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01089041
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  • 6
    Electronic Resource
    Electronic Resource
    A valine-resistant mutant of Arabidopsis thaliana displays an acetolactate synthase with altered feedback control (1994)
    Springer
    Planta 192 (1994), S. 249-255 
    Details
    ISSN: 1432-2048
    Keywords: Acetolactate synthase ; Amino acid (branched chain) ; Arabidopsis ; Feedback regulation ; Mutant ; Valine resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A valine-resistant mutant line, VAL-2, of Arabidopsis thaliana (L.) Heynh. was identified by screening M 2 populations of ethylmethane-sulfonate-mutagenized seeds. The resistance was found to be due to a single, dominant, nuclear gene mutation. Assay of acetolactate synthase (ALS) indicated that the valine resistance in this mutant is caused by decreased sensitivity of ALS to the branched-chain amino acids, valine, leucine and isoleucine. A two fold decrease in apparent K m value for pyruvate of the mutant ALS enzyme was detected compared with that of the wild type. The sensitivity of the ALS enzyme to sulfonylurea, imidazolinone and triazolopyrimidine herbicides was not altered in the mutant. At the plant growth level the mutant was also resistant to valine plus leucine, but was sensitive to leucine or isoleucine alone. The mutant gene, var1, maps, or is very closely linked, to CSR1, the gene encoding acetolactate synthase in Arabidopsis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194459
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  • 7
    Electronic Resource
    Electronic Resource
    Test of the adaptiveness of sex ratio manipulation in a parasitoid wasp (1994)
    Springer
    Behavioral ecology and sociobiology 35 (1994), S. 437-443 
    Details
    ISSN: 1432-0762
    Keywords: Adaptation ; Sex ratio ; Host size ; Parasitoid wasps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In behavioral ecology it is generally assumed that behavior is adaptive. This assumption is tested here for sex ratio manipulation in response to host size in the parasitoid wasp Spalangia cameroni. Females produce a greater proportion of daughters on larger hosts. If this behavior is adaptive, it is not through a positive effect of host size on the fitness of daughters, as theory suggests and as found for other species. Females that developed on larger hosts were not more successful at drilling into hosts, were not more successful at interspecific competition for hosts, and did not have greater dispersal ability as measured by wing loading (weight/area of wing and thorax). The possibility that S. cameroni's sex ratio manipulation may be adaptive through a negative effect of host size on the fitness of sons cannot be ruled out. Relative to males from larger hosts, males from smaller hosts had lower wing loading and thus potentially greater dispersal ability. The actual effect of wing loading on fitness remains to be tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00165847
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  • 8
    Electronic Resource
    Electronic Resource
    Test of the adaptiveness of sex ratio manipulation in a parasitoid wasp (1994)
    Springer
    Behavioral ecology and sociobiology 35 (1994), S. 437-443 
    Details
    ISSN: 1432-0762
    Keywords: Key words Adaptation ; Sex ratio ; Host size ; Parasitoid wasps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In behavioral ecology it is generally assumed that behavior is adaptive. This assumption is tested here for sex ratio manipulation in response to host size in the parasitoid wasp Spalangia cameroni. Females produce a greater proportion of daughters on larger hosts. If this behavior is adaptive, it is not through a positive effect of host size on the fitness of daughters, as theory suggests and as found for other species. Females that developed on larger hosts were not more successful at drilling into hosts, were not more successful at interspecific competition for hosts, and did not have greater dispersal ability as measured by wing loading (weight/area of wing and thorax). The possibility that S. cameroni’s sex ratio manipulation may be adaptive through a negative effect of host size on the fitness of sons cannot be ruled out. Relative to males from larger hosts, males from smaller hosts had lower wing loading and thus potentially greater dispersal ability. The actual effect of wing loading on fitness remains to be tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00165847
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  • 9
    Electronic Resource
    Electronic Resource
    Sex ratio manipulation by the parasitoid waspSpalangia cameroni in response to host age: A test of the host-size model (1990)
    Springer
    Evolutionary ecology 4 (1990), S. 149-156 
    Details
    ISSN: 1573-8477
    Keywords: Sex ratio ; parasitoid wasps ; host age ; host size ; development time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A sex ratio response to host resources as measured by external host dimensions has been demonstrated in many parasitoid wasps, includingSpalangia cameroni. The responses generally are in the direction predicted by sex ratio theory, specifically the host-size models. Here I show that femaleS. cameroni also respond to differences in resource availability not associated with changes in external host dimensions, and this response is in the direction predicted by host-size models. When given old and young hosts simultaneously, femaleS. cameroni oviposit a greater proportion of sons in old than in young host pupae, at least for 0-day old versus 3-day old hosts. Old hosts weigh less than young hosts but are not significantly different in external width. Thus it appears that the offspring sex ratio response may result from mothers detecting physical or chemical changes within the host which are associated with host age. No evidence is found that the manipulation in response to host age has been selected for via an effect of host age on wasp size; there was no significant effect of host age on either male of female wasp size. A second prediction of the host-size models is also supported by this study: when each female is presented with only a single host age, rather than two host ages simultaneously, host age has no effect on offspring sex ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02270912
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