Connecting the nutrient composition of seasonal pollens with changing nutritional needs of honey bee (Apis mellifera L.) colonies.

•Spring and fall pollens have nutrient composition that align with seasonal colony activities.•Spring bees developed larger hypopharyngeal glands when fed spring vs. fall pollen.•Hypopharyngeal glands were smaller in Nosema infected vs. uninfected spring and fall bees.•More genes were differentially expressed in spring bees fed seasonal pollens than fall bees.•Genes showed different patterns of Nosema-induced expression depending on pollen type.