Brent Colin S, Wang Meixian, Miao Yun-Gen, Hull J Joe
Arid Land Agricultural Center, USDA-ARS, Maricopa, Arizona, USA.
College of Animal Sciences, Zhejiang University, Hangzhou, People's Republic of China.
Arch Insect Biochem Physiol. 2016 Jun;92(2):108-26. doi: 10.1002/arch.21322. Epub 2016 Feb 26.
Vital physiological processes that drive the insect molt represent areas of interest for the development of alternative control strategies. The western tarnished plant bug (Lygus hesperus Knight) is a pest of numerous agronomic and horticultural crops but the development of novel control approaches is impeded by limited knowledge of the mechanisms regulating its molt. To address this deficiency, we examined the fundamental relationship underlying the hormonal and molecular components of ecdysis. At 27°C L. hesperus exhibits a temporally controlled nymph-adult molt that occurs about 4 days after the final nymph-nymph molt with ecdysteroid levels peaking 2 days prior to the final molt. Application of exogenous ecdysteroids when endogenous levels had decreased disrupted the nymphal-adult molt, with treated animals exhibiting an inability to escape the old exoskeleton and resulting in mortality compared to controls. Using accessible transcriptomic data, we identified 10 chitinase-like sequences (LhCht), eight of which had protein motifs consistent with chitinases. Phylogenetic analyses revealed orthologous relationships to chitinases critical to molting in other insects. RT-PCR based transcript profiling revealed that expression changes to four of the LhChts was coordinated with the molt period and ecdysteroid levels. Collectively, our results support a role for ecdysteroid regulation of the L. hesperus molt and suggest that cuticle clearance is mediated by LhCht orthologs of chitinases that are essential to the molt process. These results provide the initial hormonal and molecular basis for future studies to investigate the specific roles of these components in molting.
驱动昆虫蜕皮的重要生理过程是开发替代控制策略的关注领域。西部 tarnished 植物蝽（Lygus hesperus Knight）是多种农艺和园艺作物的害虫，但由于对其蜕皮调控机制的了解有限，新型控制方法的开发受到阻碍。为了弥补这一不足，我们研究了蜕皮激素和分子成分之间的基本关系。在27°C时，西部 tarnished 植物蝽表现出时间可控的若虫 - 成虫蜕皮，该蜕皮发生在最后一次若虫 - 若虫蜕皮后约4天，蜕皮甾类水平在最后一次蜕皮前2天达到峰值。在内源水平下降时应用外源蜕皮甾类会破坏若虫 - 成虫蜕皮，与对照相比，处理过的动物表现出无法脱离旧外骨骼并导致死亡。利用可获取的转录组数据，我们鉴定出10个几丁质酶样序列（LhCht），其中8个具有与几丁质酶一致的蛋白质基序。系统发育分析揭示了与其他昆虫蜕皮关键几丁质酶的直系同源关系。基于RT-PCR的转录谱分析表明，4个LhChts的表达变化与蜕皮期和蜕皮甾类水平协调一致。总体而言，我们的结果支持蜕皮甾类对西部 tarnished 植物蝽蜕皮的调节作用，并表明表皮清除是由蜕皮过程中必不可少的几丁质酶的LhCht直系同源物介导的。这些结果为未来研究这些成分在蜕皮中的具体作用提供了初步的激素和分子基础。
