Department of Plant Medicals, Andong National University, Andong 37629, Republic of Korea.
Division of Crop Cultivation and Environment Research, Department of Central Area Crop Science, National Institute of Crop Science, Rural Development Administration, Suwon 16429, Republic of Korea.
Peptides. 2018 Aug;106:28-36. doi: 10.1016/j.peptides.2018.06.006. Epub 2018 Jun 20.
A disaccharide, trehalose, is a main hemolymph sugar of the legume pod borer, Maruca vitrata larvae, but its titers fluctuated with feeding activity. During diurnal feeding in the photophase, hemolymph trehalose remained at a relatively low level (69 mM) and increased (98 mM) during scotophase. Starvation significantly increased the hemolymph trehalose level, in which the elevation of trehalose titers was dependent on the non-feeding period. The down-regulation of the trehalose level during the active feeding period seemed to result from mediation of the insulin/IGF signal (IIS). Injection of a porcine insulin suppressed the trehalose level in a dose-dependent manner. Genes associated with IIS of M. vitrata were predicted from its larval transcriptome, and their expression was confirmed in different developmental stages and tissues. All seven IIS genes selected were expressed in all developmental stages and different tissues. Silencing of four IIS genes (insulin receptor, Forkhead box O, a serine-threonine protein kinase, target of rapamycin) by RNA interference significantly modulated the hemolymph trehalose level. Starvation treatment changed expression of two trehalose metabolism-associated genes (trehalose phosphate synthase (TPS) and trehalase (TRE)) as well as the IIS genes. Silencing of TPS or TRE expression significantly down- or up-regulated the hemolymph trehalose level, respectively. In addition, silencing of IIS genes altered both TPS and TRE expression, indicating a functional link between IIS and trehalose metabolism. These results suggest that nutrients obtained from feeding activate IIS of M. vitrata, which then down-regulates the hemolymph trehalose level by altering trehalose metabolism.
海藻糖是一种二糖，是豆荚螟幼虫血淋巴中的主要糖，但它的浓度随摄食活动而波动。在光期的白天摄食时，血淋巴海藻糖保持在相对较低的水平（69 mM），而在暗期则增加（98 mM）。饥饿显著增加血淋巴海藻糖水平，其中海藻糖浓度的升高依赖于非摄食期。在活跃摄食期，海藻糖水平的下调似乎是由胰岛素/IGF 信号（IIS）介导的。猪胰岛素的注射以剂量依赖的方式抑制海藻糖水平。从幼虫转录组中预测了与 M. vitrata IIS 相关的基因，并在不同的发育阶段和组织中证实了它们的表达。选择的所有七个 IIS 基因在所有发育阶段和不同组织中都有表达。通过 RNA 干扰沉默四个 IIS 基因（胰岛素受体、Forkhead box O、丝氨酸-苏氨酸蛋白激酶、雷帕霉素靶蛋白）显著调节血淋巴海藻糖水平。饥饿处理改变了两种海藻糖代谢相关基因（海藻糖磷酸合酶（TPS）和海藻糖酶（TRE））以及 IIS 基因的表达。TPS 或 TRE 表达的沉默显著下调或上调血淋巴海藻糖水平，分别。此外，IIS 基因的沉默改变了 TPS 和 TRE 的表达，表明 IIS 和海藻糖代谢之间存在功能联系。这些结果表明，摄食获得的营养物质激活了 M. vitrata 的 IIS，然后通过改变海藻糖代谢来下调血淋巴海藻糖水平。
