Genetic and environmental effects on the expression of peptidases and larval viability in Drosophila melanogaster.
Genetic and environmental effects on the expression of peptidases and larval viability in Drosophila melanogaster.
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遗传和环境对果蝇肽酶表达和幼虫活力的影响。
DOI：
10.1093/genetics/131.3.625
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发表时间：
1992
期刊：
影响因子：
3.3
通讯作者：
Mathes,KD
中科院分区：
文献类型：
--
作者：
Hiraizumi,K;Tavormina,PA;Mathes,KD
以果蝇肽酶系统（由二肽酶-A、二肽酶-B、二肽酶-C 和亮氨酸氨基肽酶组成）为模型，研究酶活性变异的适应性意义。肽酶活性在几乎所有组织中的普遍分布以及血淋巴中氨基酸和寡肽的高浓度表明肽酶参与渗透调节。在这一假设下，幼虫通过在细胞内和细胞外将肽水解成氨基酸以增加生理渗透浓度来抵消环境渗透应激的增加。通过测定等基因系第三龄幼虫中的肽酶活性来研究肽酶的表达，这些幼虫是在使用D-甘露醇或NaCl的环境渗透胁迫水平增加的情况下饲养的。第二和第三染色体取代等基因系用于评估调节基因和结构基因在酶活性变异中的相对贡献。结果表明：（1）肽酶活性存在遗传变异，（2）渗透胁迫的影响在肽酶之间差异很大，（3）响应渗透胁迫的肽酶活性变化取决于遗传背景和渗透效应子，（4）肽酶活性彼此相关，但这些表型相关性取决于遗传背景、渗透效应子和渗透胁迫水平。幼虫血淋巴中的渗透浓度与亮氨酸氨基肽酶活性相关，但响应环境渗透胁迫的血淋巴渗透浓度的变化取决于环境中的渗透效应器。尽管这些发现表明遗传和环境因素对具有相似功能的酶的表达有显着贡献，但对二肽酶-B (DIP-B) 活性显着差异的基因型的相对幼虫活力研究表明，在环境渗透胁迫水平增加的情况下，低 DIP-B 活性并不会导致幼虫活力出现任何可测量的降低。这些阴性结果表明，要么 DIP-B 在渗透压调节中不起主要作用，要么渗透压调节差异与这些测试中卵到成虫的活力无关。
The peptidase system in Drosophila melanogaster, consisting of dipeptidase-A, dipeptidase-B, dipeptidase-C and the leucine aminopeptidases, was used as a model to study the adaptive significance of enzyme activity variation. The involvement of the peptidases in osmoregulation has been suggested from the ubiquitous distribution of peptidase activities in nearly all tissues and the high concentration of amino acids and oligopeptides in the hemolymph. Under this hypothesis, larvae counteract increases in environmental osmotic stress by hydrolyzing peptides into amino acids both intra- and extracellularly to increase physiological osmotic concentration. The expression of the peptidases was studied by assaying for peptidase activities in third instar larvae of isogenic lines, which were reared under increasing levels of environmental osmotic stress using either D-mannitol or NaCl. Second and third chromosome substitution isogenic lines were used to assess the relative contribution of regulatory and structural genes in enzyme activity variation. Results indicate that: (1) genetic variation exists for peptidase activities, (2) the effect of osmotic stress is highly variable among peptidases, (3) changes in peptidase activities in response to osmotic stress depend on both genetic background and osmotic effector and (4) peptidase activities are correlated with each other, but these phenotypic correlations depend on genetic background, osmotic effector, and level of osmotic stress. Osmotic concentration in the larval hemolymph is correlated with leucine aminopeptidase activity, but changes in hemolymph osmotic concentration in response to environmental osmotic stress depend on the osmotic effector in the environment. Although these findings suggest that genetic and environmental factors contribute significantly toward the expression of enzymes with similar functions, a relative larval viability study of genotypes that differed significantly in dipeptidase-B (DIP-B) activity revealed that low DIP-B activity did not confer any measurable reduction in larval viability under increasing levels of environmental osmotic stress. These negative results suggest that, either DIP-B does not play a major role in osmoregulation or differential osmoregulation is not related to egg to adult viability in these tests.