Anhydrobiosis Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8634, Japan.
IUBMB Life. 2011 Jun;63(6):419-29. doi: 10.1002/iub.463. Epub 2011 May 5.
An African chironomid, Polypedilum vanderplanki, is the only insect known to be capable of extreme desiccation tolerance, or anhydrobiosis. In the 1950s and 1960s, Hinton strenuously studied anhydrobiosis in this insect from a physiological standpoint; however, nobody has afterward investigated the phenomenon. In 2000, research on mechanisms underlying anhydrobiosis was resumed due to successful establishment of a rearing system for P. vanderplanki. This review is focused on the latest findings on the physiological and molecular mechanisms underlying the induction of anhydrobiosis in P. vanderplanki. Early experiments demonstrated that the induction of anhydrobiosis was possible in isolated tissues and independent from the control of central nervous system. However, to achieve successful anhydrobiosis, larvae need a slow regime of desiccation, allowing them to synthesize molecules, which will protect cells and tissues against the deleterious effects of dehydration. Trehalose, a nonreducing disaccharide, which accumulates in P. vanderplanki larvae up to 20% of the dry body mass, is thought to replace the water in its tissues. Similarly, highly hydrophilic proteins called the late embryogenesis abundant (LEA) proteins are expressed in huge quantities and act as a molecular shield to protect biological molecules against aggregation and denaturation. This function is shared by heat shock proteins, which are also upregulated during the desiccation process. At the same time, desiccating larvae express various antioxidant molecules and enzymes, to cope with the massive oxidative stress, which is responsible for general damage to membranes, proteins, and DNA in dehydrating cells. Finally, specific water channels, called aquaporins, accelerate dehydration, and trehalose together with LEA proteins forms a glassy matrix, which protects the biological molecules and the structural integrity of larvae in the anhydrobiotic state.
一种非洲摇蚊，即 Polypedilum vanderplanki，是唯一已知能够具有极端干燥耐受性或脱水休眠能力的昆虫。在 20 世纪 50 年代和 60 年代，Hinton 从生理学角度对这种昆虫的脱水休眠进行了艰苦的研究；然而，此后没有人对这种现象进行过调查。由于成功建立了 P. vanderplanki 的饲养系统，2000 年重新开始研究脱水休眠的机制。这篇综述重点介绍了关于 P. vanderplanki 脱水休眠诱导的生理和分子机制的最新发现。早期的实验表明，在孤立的组织中诱导脱水休眠是可能的，并且独立于中枢神经系统的控制。然而，要实现成功的脱水休眠，幼虫需要缓慢的干燥过程，使它们能够合成分子，这些分子将保护细胞和组织免受脱水的有害影响。海藻糖是一种非还原二糖，在 P. vanderplanki 幼虫中积累到干体重的 20%，被认为可以替代组织中的水分。同样，大量表达的高度亲水性蛋白质，即晚期胚胎丰富（LEA）蛋白，作为分子护盾，防止生物分子聚集和变性。这种功能与热休克蛋白共享，热休克蛋白在干燥过程中也被上调。同时，干燥的幼虫表达各种抗氧化分子和酶，以应对导致细胞膜、蛋白质和脱水细胞中 DNA 普遍损伤的大量氧化应激。最后，特定的水通道，称为水通道蛋白，加速脱水，海藻糖与 LEA 蛋白一起形成玻璃状基质，保护脱水休眠状态下的生物分子和幼虫的结构完整性。
