Data from: Altered expression of pectoral myosin heavy chain isoforms corresponds to migration status in the white-crowned sparrow (Zonotrichia leucophrys gambelii)

Birds undergo numerous changes as they progress through life-history stages, yet relatively few studies have examined how birds adapt to both the dynamic energetic and mechanical demands associated with such transitions. Myosin heavy chain (MyHC) expression, often linked with muscle fibre type, is strongly correlated with a muscle's mechanical power-generating capability, thus we examined several morphological properties, including MyHC expression of the pectoralis, in a long-distance migrant, the white-crowned sparrow (Zonotrichia leucophrys gambelii) throughout the progression from winter, spring departure and arrival on breeding grounds. White-crowned sparrows demonstrated significant phenotypic flexibility throughout the seasonal transition, including changes in prealternate moult status, lipid fuelling, body condition and flight muscle morphology. Pectoral MyHC expression also varied significantly over the course of the study. Wintering birds expressed a single, newly classified adult fast 2 isoform. At spring departure, pectoral isoform expression included two MyHC isoforms: the adult fast 2 isoform along with a smaller proportion of a newly present adult fast 1 isoform. By spring arrival, both adult fast isoforms present at departure remained, yet expression had shifted to a greater relative proportion of the adult fast 1 isoform. Altering pectoral MyHC isoform expression in preparation for and during spring migration may represent an adaptation to modulate muscle mechanical output to support long-distance flight.

鸟类在经历不同生活史阶段时会发生诸多适应性变化，但目前鲜有研究探讨鸟类如何同时适应此类转变所伴随的动态能量需求与机械负荷。肌球蛋白重链（Myosin heavy chain, MyHC）的表达通常与肌纤维类型密切相关，且与肌肉的机械功率产生能力显著相关，因此我们以长途迁徙鸟类白冠带鹀（Zonotrichia leucophrys gambelii）为研究对象，对其从越冬、春季迁徙启程直至抵达繁殖地的全过程中，包括胸肌MyHC表达在内的多项形态学特征进行了检测。研究结果显示，白冠带鹀在季节性转变过程中表现出显著的表型可塑性，具体涵盖换羽前期状态、脂质蓄积水平、身体状况以及飞行肌肉形态的变化。胸肌MyHC的表达谱在整个研究周期内同样存在显著差异。越冬个体仅表达一种新分类的成年快肌2亚型。春季迁徙启程时，胸肌可检测到两种MyHC亚型：成年快肌2亚型，以及占比相对较低的新出现的成年快肌1亚型。至春季抵达繁殖地时，启程阶段存在的两种成年快肌亚型均得以保留，但表达谱已转向成年快肌1亚型占比更高的状态。在春季迁徙准备阶段及迁徙过程中，调整胸肌MyHC亚型的表达模式，或代表一种适应性策略，用以调节肌肉机械输出以支持长距离飞行。