Pujol-Lereis Luciana Mercedes, Rabossi Alejandro, Quesada-Allué Luis Alberto
Instituto de Investigaciones Bioquímicas de Buenos Aires (IIBBA), CONICET, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Fundación Instituto Leloir, Buenos Aires, Argentina.
J Insect Physiol. 2014 Dec;71:156-63. doi: 10.1016/j.jinsphys.2014.10.015. Epub 2014 Nov 4.
The medfly Ceratitis capitata is an agricultural pest distributed worldwide thanks, in part, to its phenotypic plasticity of thermal tolerance. Cold exposure has been shown to reduce C. capitata survival, which may affect its distribution in areas with subfreezing temperatures. When insects are increasingly cooled, they attain a critical thermal threshold and enter a chill-coma state characterized by cessation of movement. It is not clear how a rapid cold exposure affects the physiological state of medflies, and how this is influenced by age and population heterogeneity. In order to approach these questions, C. capitata single-sex laboratory populations of 15 and 30 days old were subjected to a chill-coma recovery assay, and separated according to their recovery time in three subgroups: Fast-Subgroups, Intermediate-Subgroups, and Slow-Subgroups. Thereafter, we analyzed their survival, behavioral, and gene expression outputs. In female and old male populations, we found that flies with the slowest recovery time had a reduced life expectancy, a higher initial mortality rate, and a worse climbing performance compared with flies that recovered faster. Therefore, we were able to separate subgroups that developed chilling-injury from subgroups that had a reversible full recovery after cold exposure. The gene expression analysis of the heat shock protein genes hsp70 and hsp83 showed no clear association with the parameters studied. Interestingly, thorax expression levels of the Cu/Zn superoxide dismutase gene were elevated during the recovery phase in the Fast-Subgroups, but remained constant in the Slow-Subgroups that developed chilling-injury. On the other hand, none of the young male subgroups seemed to have suffered irreversible damage. Thus, we concluded that depending on age and population heterogeneity, chill-coma recovery time points out significant differences on individual cold tolerance. Moreover, the inability to properly induce the antioxidant defense system to counteract the oxidative damage caused by cold seems to contribute to the development of chilling-injury.
地中海实蝇Ceratitis capitata是一种农业害虫，广泛分布于世界各地，部分原因在于其对热耐受性的表型可塑性。研究表明，低温暴露会降低地中海实蝇的存活率，这可能会影响其在温度低于冰点地区的分布。当昆虫逐渐冷却时，它们会达到一个临界热阈值并进入冷昏迷状态，其特征是停止运动。目前尚不清楚快速冷暴露如何影响地中海实蝇的生理状态，以及这如何受到年龄和种群异质性的影响。为了探讨这些问题，对15日龄和30日龄的地中海实蝇单性实验室种群进行了冷昏迷恢复试验，并根据其恢复时间分为三个亚组：快速亚组、中间亚组和缓慢亚组。此后，我们分析了它们的存活、行为和基因表达结果。在雌性和老龄雄性种群中，我们发现恢复时间最慢的果蝇与恢复较快的果蝇相比，预期寿命缩短、初始死亡率较高且攀爬能力较差。因此，我们能够将发生冷损伤的亚组与冷暴露后完全可逆恢复的亚组区分开来。热休克蛋白基因hsp70和hsp83的基因表达分析表明，它们与所研究的参数没有明显关联。有趣的是，快速亚组在恢复阶段铜/锌超氧化物歧化酶基因的胸部表达水平升高，但在发生冷损伤的缓慢亚组中保持不变。另一方面，年轻雄性亚组似乎都没有遭受不可逆转的损伤。因此，我们得出结论，根据年龄和种群异质性，冷昏迷恢复时间指出了个体耐寒性的显著差异。此外，无法适当诱导抗氧化防御系统来抵消寒冷引起的氧化损伤似乎有助于冷损伤的发展。
