Laboratory of Developmental Biology, Division of Life Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
Laboratory of Developmental Biology and Physiology, Department of Science, Ibaraki University, 1-1-2 Bunkyo, Mito, 310-8512, Japan.
J Comp Physiol B. 2021 May;191(3):439-453. doi: 10.1007/s00360-021-01350-4. Epub 2021 Feb 13.
Nutritional signals strictly control post-embryonic development in insects. Dietary carbohydrates are hydrolyzed to monosaccharides in the gut and then transported into the hemolymph. These monosaccharides in hemolymph are rapidly taken up by tissues and utilized in glycolysis, the pentose phosphate shunt, and glycogen or trehalose synthesis. These metabolic pathways are essential for nutrient metabolism; therefore, the control of carbohydrate digestion is indispensable for maintaining energy supply during development. Carbohydrate digestion was believed to be controlled by dietary mechanisms. We previously reported that hormonal and developmental controls participate in the regulation of carbohydrate digestion during larval-pupal metamorphosis. However, it is unclear whether this regulatory mechanism also works during larval-larval molting and inter-molt feeding period. Here, we show that control mechanisms of the carbohydrate digestion show sequential changes that are controlled by different mechanisms. In the penultimate larval instar, carbohydrate hydrolysis activity changed depending on developmental progress and dietary state. Maltose- and sucrose-hydrolysis activity were suppressed by ecdysteroid, an insect steroid hormone. During the inter-molt feeding period, carbohydrate hydrolysis activities were grouped as either nutrient-sensitive or nutrient-insensitive. Although the activity in both groups was suppressed by ecdysteroid, this hormonal regulatory machinery remains in an "off-state" because ecdysteroid is scarce during the feeding period, suggesting that the carbohydrate digestion system is exclusively regulated by the dietary state during inter-molt feeding period.
营养信号严格控制昆虫的胚胎后发育。膳食中的碳水化合物在肠道中水解成单糖,然后运输到血淋巴中。这些血淋巴中的单糖被组织迅速吸收,并用于糖酵解、戊糖磷酸支路和糖原或海藻糖合成。这些代谢途径对于营养物质代谢是必不可少的;因此,碳水化合物消化的控制对于维持发育过程中的能量供应是不可或缺的。碳水化合物消化被认为是由饮食机制控制的。我们之前报道过,激素和发育控制参与了幼虫-蛹变态期间碳水化合物消化的调节。然而,尚不清楚这种调节机制是否也在幼虫-幼虫蜕皮和蜕皮间期摄食期间起作用。在这里,我们表明碳水化合物消化的控制机制表现出顺序变化,受不同机制控制。在倒数第二个幼虫龄期,碳水化合物水解活性根据发育进展和饮食状态而变化。麦芽糖和蔗糖水解活性受昆虫类固醇激素蜕皮激素的抑制。在蜕皮间期摄食期间,碳水化合物水解活性被分为营养敏感型或营养不敏感型。尽管这两组的活性都被蜕皮激素抑制,但这种激素调节机制仍然处于“关闭状态”,因为蜕皮激素在摄食期间稀少,这表明碳水化合物消化系统在蜕皮间期摄食期间仅受饮食状态调节。