Zhao Zhangwu, Zera Anthony J
School of Biological Sciences, University of Nebraska, Lincoln, NE 68588, USA.
J Insect Physiol. 2006 Jun;52(6):646-58. doi: 10.1016/j.jinsphys.2006.03.003. Epub 2006 Mar 12.
The biochemical basis of specializations for dispersal vs. reproduction is an understudied aspect of dispersal polymorphism in insects. Using a radiolabelled amino acid, we quantified differences in in vivo amino acid metabolism between morphs of the wing-polymorphic cricket, Gryllus firmus, that trade-off early age reproduction and dispersal capability. Studies were conducted in crickets fed a variety of diets expected to influence amino acid and lipid metabolism. On the day of molt to adulthood, prior to the morph-specific trade-off between ovarian growth and biochemical preparation for flight (e.g. biosynthesis of triglyceride flight fuel), morphs did not differ in any aspect of amino acid metabolism. However, on day 5 of adulthood, when the morph-specific trade-off between ovarian growth and flight fuel production was manifest, the morphs differed substantially in each of the three aspects of amino acid metabolism studied: conversion to protein, oxidation, and conversion to lipid. Morphs also differed in degree of allocation of products of amino acid metabolism to ovaries vs. the soma. Most importantly, morphs differed in the relative metabolism of radiolabelled glycine through these pathways (i.e. biochemical trade-offs), and in the relative allocation of end products of amino acid metabolism to the soma vs. ovaries (allocation trade-offs). A functionally important interaction between amino acid and lipid metabolism was noted: greater oxidation of amino acids in the flight-capable morph spared fatty acids for enhanced conversion into triglyceride flight fuel. By contrast, greater oxidation of fatty acids by the flightless morph spared amino acids for enhanced conversion into ovarian protein. Diet significantly affected amino acid metabolism. However, MORPHxDIET interactions were rare and morphs differed in amino acid metabolism to a similar degree under the range of diets tested.
扩散与繁殖特化的生化基础是昆虫扩散多态性中一个研究较少的方面。我们使用放射性标记的氨基酸，量化了翅多型蟋蟀（Gryllus firmus）不同形态之间体内氨基酸代谢的差异，这些形态在早期繁殖和扩散能力之间进行权衡。研究在喂食各种预期会影响氨基酸和脂质代谢的食物的蟋蟀中进行。在蜕皮至成年的当天，在卵巢生长与飞行生化准备（例如甘油三酯飞行燃料的生物合成）之间进行形态特异性权衡之前，各形态在氨基酸代谢的任何方面都没有差异。然而，在成年第5天，当卵巢生长与飞行燃料产生之间的形态特异性权衡显现时，在所研究的氨基酸代谢的三个方面，各形态存在显著差异：转化为蛋白质、氧化以及转化为脂质。各形态在氨基酸代谢产物分配到卵巢与躯体的程度上也存在差异。最重要的是，各形态在放射性标记甘氨酸通过这些途径的相对代谢（即生化权衡）以及氨基酸代谢终产物在躯体与卵巢之间的相对分配（分配权衡）方面存在差异。注意到氨基酸和脂质代谢之间存在功能上重要的相互作用：有飞行能力的形态中氨基酸的更大氧化节省了脂肪酸，以增强其转化为甘油三酯飞行燃料。相比之下，无飞行能力的形态中脂肪酸的更大氧化节省了氨基酸，以增强其转化为卵巢蛋白。食物显著影响氨基酸代谢。然而，形态×食物的相互作用很少见，并且在测试的食物范围内，各形态在氨基酸代谢方面的差异程度相似。
