Department of Clinical Pharmacology, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan.
Support Center for Medical Research and Education, Tokai University, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan.
Sci Rep. 2020 Apr 24;10(1):7005. doi: 10.1038/s41598-020-63961-1.
Although the fighting behaviour in gamecocks has evolved because of artificial selection, it is unknown whether the selection for aggressiveness affects neurotransmitter levels in the avian central nervous system. We sought to identify the source and origin of this trait. We collected the brain samples from 6 female Shamo gamecocks and 5 Shaver Brown chickens (control; bred for egg production). The midbrain levels of norepinephrine (NE) were significantly higher in Shamo gamecocks (P = 0.0087) than in the controls. Moreover, alleles encoding adrenergic receptors differed between the breeds in terms of response to NE. Gene mutations specific to Shamo and potentially associated with fighting behaviour were in sites T440N of ADRα1D; V296I of ADRα2A; and T44I, Q232R, and T277M of ADRβ2. The evolutionary analysis indicated that the ADRβ2 (T44I and Q232R) mutations were heritable in all Galliformes, whereas the T440N mutation of ADRα1D and V296I mutations of ADRα2A were unique to Shamo and originated by artificial selection. A high NE level may confer a selective advantage by enabling gamecocks to be aggressive and pain tolerant. Therefore, the strong fighting behaviour of Shamo has resulted from a combination of naturally inherited and mutant genes derived by artificial selection.
尽管斗鸡的战斗行为是由于人工选择而进化的，但攻击性的选择是否会影响鸟类中枢神经系统中的神经递质水平尚不清楚。我们试图确定这种特性的来源和起源。我们从 6 只雌性 Shamo 斗鸡和 5 只 Shaver Brown 鸡（对照组；用于产蛋）中采集了脑组织样本。Shamo 斗鸡的中脑去甲肾上腺素（NE）水平明显高于对照组（P=0.0087）。此外，两种品种的肾上腺素能受体基因编码在对 NE 的反应方面存在差异。Shamo 特有的、可能与战斗行为相关的基因突变位于 ADRα1D 的 T440N；ADRα2A 的 V296I；ADRβ2 的 T44I、Q232R 和 T277M。进化分析表明，ADRβ2（T44I 和 Q232R）突变在所有雉科动物中都是可遗传的，而 ADRα1D 的 T440N 突变和 ADRα2A 的 V296I 突变是 Shamo 所特有的，是由人工选择产生的。高 NE 水平可能通过使斗鸡具有攻击性和耐痛性而赋予选择性优势。因此，Shamo 强烈的战斗行为是由自然遗传和人工选择衍生的突变基因共同作用的结果。
