Carl Hayden Bee Research Center, USDA-ARS, Tucson, AZ, USA.
Carl Hayden Bee Research Center, USDA-ARS, Tucson, AZ, USA.
J Insect Physiol. 2018 Aug-Sep;109:114-124. doi: 10.1016/j.jinsphys.2018.07.002. Epub 2018 Jul 7.
Free-ranging herbivores have yearly life cycles that generate dynamic resource needs. Honey bee colonies also have a yearly life cycle that might generate nutritional requirements that differ between times of brood rearing and colony expansion in the spring and population contraction and preparation for overwintering in the fall. To test this, we analyzed polyfloral mixes of spring and fall pollens to determine if the nutrient composition differed with season. Next, we fed both types of seasonal pollens to bees reared in spring and fall. We compared the development of brood food glands (i.e., hypopharyngeal glands - HPG), and the expression of genes in the fat body between bees fed pollen from the same (in-season) or different season (out-of-season) when they were reared. Because pathogen challenges often heighten the effects of nutritional stress, we infected a subset of bees with Nosema to determine if bees responded differently to the infection depending on the seasonal pollen they consumed. We found that spring and fall pollens were similar in total protein and lipid concentrations, but spring pollens had higher concentrations of amino and fatty acids that support HPG growth and brood production. Bees responded differently when fed in vs. out of season pollen. The HPG of both uninfected and Nosema-infected spring bees were larger when they were fed spring (in-season) compared to fall pollen. Spring bees differentially regulated more than 200 genes when fed in- vs. out-of-season pollen. When infected with Nosema, approximately 400 genes showed different infection-induced expression patterns in spring bees depending on pollen type. In contrast, HPG size in fall bees was not affected by pollen type, though HPG were smaller in those infected with Nosema. Very few genes were differentially expressed with pollen type in uninfected (4 genes) and infected fall bees (5 genes). Pollen type did not affect patterns of infection-induced expression in fall bees. Our data suggest that physiological responses to seasonal pollens differ between bees reared in the spring and fall with spring bees being significantly more sensitive to pollen type especially when infected with Nosema. This study provides evidence that seasonal pollens may provide levels of nutrients that align with the activities of honey bees during their yearly colony cycle. The findings are important for the planning and establishment of forage plantings to sustain honey bees, and in the development of seasonal nutritional supplements fed to colonies when pollen is unavailable.
自由放养的草食动物的生命周期是动态的，每年都会产生不同的资源需求。蜜蜂的生命周期也具有季节性，在春季繁殖和蜂群扩张以及秋季种群收缩和准备越冬期间，可能会产生不同的营养需求。为了验证这一点，我们分析了春季和秋季花粉的混合花粉，以确定营养成分是否随季节而变化。接下来，我们用春季和秋季采集的两种季节性花粉喂养蜜蜂。我们比较了在春季和秋季饲养的蜜蜂的幼虫食物腺（即下咽腺 - HPG）和脂肪体中的基因表达，比较了用同季（当季）或不同季（非当季）的花粉饲养的蜜蜂的发育情况。由于病原体的挑战通常会加剧营养压力的影响，我们用Nosema 感染了一部分蜜蜂，以确定蜜蜂在食用不同季节的花粉时，对感染的反应是否不同。我们发现，春季和秋季花粉在总蛋白质和脂质浓度上相似，但春季花粉中支持 HPG 生长和幼虫生产的氨基酸和脂肪酸浓度更高。当蜜蜂喂食当季或非当季花粉时，反应不同。当用春季（当季）花粉而不是秋季花粉喂养时，未感染和感染 Nosema 的春季蜜蜂的 HPG 都更大。当用当季或非当季花粉喂养时，春季蜜蜂差异调控了 200 多个基因。当感染 Nosema 时，约 400 个基因在春季蜜蜂中表现出不同的感染诱导表达模式，这取决于花粉类型。相比之下，秋季蜜蜂的 HPG 大小不受花粉类型的影响，但感染 Nosema 的 HPG 较小。在未感染（4 个基因）和感染的秋季蜜蜂（5 个基因）中，很少有基因的表达与花粉类型不同。花粉类型对秋季蜜蜂的感染诱导表达模式没有影响。我们的数据表明，在春季和秋季饲养的蜜蜂中，对季节性花粉的生理反应不同，春季蜜蜂对花粉类型更为敏感，尤其是在感染 Nosema 时。这项研究提供了证据表明，季节性花粉可能提供与蜜蜂在其年度群体周期中活动相匹配的营养水平。这些发现对于规划和建立养蜂植物种植以维持蜜蜂种群以及在花粉不可用时为蜂群提供季节性营养补充剂的发展都很重要。
