Kalra Bhawna, Tamang Aditya Moktan, Parkash Ravi
Department of Genetics, M. D. University, Rohtak 124001, India.
Department of Genetics, M. D. University, Rohtak 124001, India.
Comp Biochem Physiol A Mol Integr Physiol. 2017 Jul;209:65-73. doi: 10.1016/j.cbpa.2017.04.014. Epub 2017 Apr 25.
Some insect taxa from polar or temperate habitats have shown cross-tolerance for multiple stressors but tropical insect taxa have received less attention. Accordingly, we considered adult flies of a tropical drosophilid-Zaprionus indianus for testing direct as well as cross-tolerance effects of rapid heat hardening (HH), desiccation acclimation (DA) and starvation acclimation (SA) after rearing under warmer and drier season specific simulated conditions. We observed significant direct acclimation effects of HH, DA and SA; and four cases of cross-tolerance effects but no cross-tolerance between desiccation and starvation. Cross-tolerance due to heat hardening on desiccation showed 20% higher effect than its reciprocal effect. There is greater reduction of water loss in heat hardened flies (due to increase in amount of cuticular lipids) as compared with desiccation acclimated flies. However, cross-tolerance effect of SA on heat knockdown was two times higher than its reciprocal. Heat hardened and desiccation acclimated adult flies showed substantial increase in the level of trehalose and proline while body lipids increased due to heat hardening or starvation acclimation. However, maximum increase in energy metabolites was stressor specific i.e. trehalose due to DA; proline due to HH and total body lipids due to SA. Rapid changes in energy metabolites due to heat hardening seem compensatory for possible depletion of trehalose and proline due to desiccation stress; and body lipids due to starvation stress. Thus, observed cross-tolerance effects in Z. indianus represent physiological changes to cope with multiple stressors related to warmer and drier subtropical habitats.
一些来自极地或温带栖息地的昆虫类群已表现出对多种应激源的交叉耐受性，但热带昆虫类群受到的关注较少。因此，我们考虑了一种热带果蝇——印度果蝇的成虫，在模拟的温暖干燥季节特定条件下饲养后，测试快速热硬化（HH）、干燥驯化（DA）和饥饿驯化（SA）的直接耐受性以及交叉耐受性影响。我们观察到HH、DA和SA具有显著的直接驯化效应；以及四种交叉耐受性效应的情况，但干燥和饥饿之间没有交叉耐受性。热硬化对干燥的交叉耐受性效应比其反向效应高20%。与干燥驯化的果蝇相比，热硬化的果蝇（由于表皮脂质含量增加）水分流失的减少幅度更大。然而，SA对热击倒的交叉耐受性效应是其反向效应的两倍。热硬化和干燥驯化的成年果蝇海藻糖和脯氨酸水平大幅增加，而身体脂质因热硬化或饥饿驯化而增加。然而，能量代谢物的最大增加是应激源特异性的，即DA导致海藻糖增加；HH导致脯氨酸增加，SA导致全身脂质增加。热硬化导致的能量代谢物快速变化似乎是对干燥应激可能导致的海藻糖和脯氨酸消耗以及饥饿应激导致的身体脂质消耗的补偿。因此，在印度果蝇中观察到的交叉耐受性效应代表了应对与温暖干燥的亚热带栖息地相关的多种应激源的生理变化。
