Sasaki Ken, Yoshimura Hideto, Yokoi Kakeru
Graduate School of Agriculture, Tamagawa University, Machida, Tokyo, Japan.
Division of Crop Rotation Research for Lowland Farming, Tohoku Agricultural Research Center, NARO, Morioka, Iwate, Japan.
Sci Rep. 2024 Dec 5;14(1):30399. doi: 10.1038/s41598-024-80745-z.
Adult females of the primitively eusocial wasp Polistes jokahamae can change caste in response to photoperiod length. Short-day photoperiod females store more lipids but have less developed ovaries for hibernation (becoming gynes), whereas long-day photoperiod females have fewer lipid stores but more developed ovaries under queenless conditions (becoming egg-laying workers). To explore the physiological mechanisms underlying photoperiod-related caste determination, analyses of gene expression levels in the brains of short- or long-day females were performed. Results suggest that short-day females may exhibit higher expression of genes involved in tryptophan metabolism, insulin signaling, and nutrition, including the digestion of sugars and lipids, and production of royal jelly proteins. Oral administration of tryptophan resulted in a positive correlation between tryptophan levels in the brain and lipid stores in the abdomen, suggesting that tryptophan promotes lipid storage in gynes. Long-day females showed enhanced expression of genes involved in tyramine/dopamine syntheses, epidermal growth factor receptor, insulin degradation, and oogenesis. In these females, tyramine administration increased the brain levels of tyramine and dopamine, and activated initial ovarian development under queenless conditions. Together, these results indicate that photoperiod-related caste determination in P. jokahamae may involve gene expression pathways similar to those involved in caste determination during the preimaginal stage in other Polistes species.
原始真社会性黄蜂日本长脚胡蜂的成年雌性会根据光周期长度改变品级。短日照光周期的雌性储存更多脂质，但卵巢发育程度较低以进行冬眠（成为雌蜂），而长日照光周期的雌性脂质储存较少，但在无蜂王条件下卵巢发育程度更高（成为产卵工蜂）。为了探究光周期相关品级决定的生理机制，对短日照或长日照雌性黄蜂大脑中的基因表达水平进行了分析。结果表明，短日照雌性可能在参与色氨酸代谢、胰岛素信号传导和营养（包括糖和脂质的消化以及蜂王浆蛋白的产生）的基因上表现出更高的表达。口服色氨酸导致大脑中的色氨酸水平与腹部的脂质储存之间呈正相关，这表明色氨酸促进雌蜂的脂质储存。长日照雌性在参与酪胺/多巴胺合成、表皮生长因子受体、胰岛素降解和卵子发生的基因上表现出增强的表达。在这些雌性中，给予酪胺会增加大脑中酪胺和多巴胺的水平，并在无蜂王条件下激活卵巢的初始发育。总之，这些结果表明，日本长脚胡蜂中与光周期相关的品级决定可能涉及与其他长脚胡蜂物种在成虫前期阶段的品级决定中所涉及的类似基因表达途径。
