Popović Željko D, Maier Vítězslav, Avramov Miloš, Uzelac Iva, Gošić-Dondo Snežana, Blagojević Duško, Koštál Vladimír
Department of Biology and Ecology, Faculty of Sciences, University of Novi Sad, Novi Sad, Serbia.
Department of Analytical Chemistry, Faculty of Science, Palacký University, Olomouc, Czechia.
Front Physiol. 2021 Nov 22;12:768593. doi: 10.3389/fphys.2021.768593. eCollection 2021.
The European corn borer is a pest species, whose fifth instar larvae gradually develop cold hardiness during diapause. The physiological changes underlying diapause progression and cold hardiness development are still insufficiently understood in insects. Here, we follow a complex of changes related to energy metabolism during cold acclimation (5°C) of diapausing larvae and compare this to warm-acclimated (22°C) and non-diapause controls. Capillary electrophoresis of nucleotides and coenzymes has shown that in gradually cold-acclimated groups concentrations of ATP/ADP and, consequently, energy charge slowly decrease during diapause, while the concentration of AMP increases, especially in the first months of diapause. Also, the activity of cytochrome oxidase (COX), as well as the concentrations of NAD and GMP, decline in cold-acclimated groups, until the latter part of diapause, when they recover. Relative expression of NADH dehydrogenase (), coenzyme Q-cytochrome reductase (), COX, ATP synthase (), ADP/ATP translocase (), and prohibitin 2 () is supressed in cold-acclimated larvae during the first months of diapause and gradually increases toward the termination of diapause. Contrary to this, NADP and UMP levels significantly increased in the first few months of diapause, after gradual cold acclimation, which is in connection with the biosynthesis of cryoprotective molecules, as well as regeneration of small antioxidants. Our findings evidence the existence of a cold-induced energy-saving program that facilitates long-term maintenance of larval diapause, as well as gradual development of cold hardiness. In contrast, warm acclimation induced faster depletion of ATP, ADP, UMP, NAD, and NADP, as well as higher activity of COX and generally higher expression of all energy-related genes in comparison to cold-acclimated larvae. Moreover, such unusually high metabolic activity, driven by high temperatures, lead to premature mortality in the warm-acclimated group after 2 months of diapause. Thus, our findings strongly support the importance of low temperature exposure in early diapause for gradual cold hardiness acquisition, successful maintenance of the resting state and return to active development. Moreover, they demonstrate potentially adverse effects of global climate changes and subsequent increase in winter temperatures on cold-adapted terrestrial organisms in temperate and subpolar regions.
欧洲玉米螟是一种害虫，其五龄幼虫在滞育期间逐渐形成耐寒性。昆虫滞育进程和耐寒性发展背后的生理变化仍未得到充分了解。在此，我们追踪了滞育幼虫在冷驯化（5°C）期间与能量代谢相关的一系列变化，并将其与暖驯化（22°C）和非滞育对照进行比较。核苷酸和辅酶的毛细管电泳显示，在逐渐冷驯化的组中，ATP/ADP的浓度以及能量电荷在滞育期间缓慢下降，而AMP的浓度增加，尤其是在滞育的头几个月。此外，冷驯化组中细胞色素氧化酶（COX）的活性以及NAD和GMP的浓度下降，直到滞育后期才恢复。在滞育的头几个月，冷驯化幼虫中NADH脱氢酶（）、辅酶Q - 细胞色素还原酶（）、COX、ATP合酶（）、ADP/ATP转位酶（）和抑制素2（）的相对表达受到抑制，并在滞育结束时逐渐增加。与此相反，在逐渐冷驯化后，滞育的头几个月中NADP和UMP水平显著增加，这与抗冻分子的生物合成以及小抗氧化剂的再生有关。我们的研究结果证明存在一种冷诱导的节能程序，该程序有助于幼虫滞育的长期维持以及耐寒性的逐渐发展。相比之下，与冷驯化幼虫相比，暖驯化导致ATP、ADP、UMP、NAD和NADP更快消耗，以及COX活性更高，所有与能量相关基因的表达普遍更高。此外，由高温驱动的这种异常高的代谢活性导致暖驯化组在滞育2个月后过早死亡。因此，我们的研究结果有力地支持了滞育早期暴露于低温对于逐渐获得耐寒性、成功维持静止状态以及恢复活跃发育的重要性。此外，它们证明了全球气候变化以及随后冬季温度升高对温带和亚极地地区适应寒冷的陆地生物的潜在不利影响。
