High-Fat Diets with Differential Fatty Acids Induce Obesity and Perturb Gut Microbiota in Honey Bee.

HFD (high-fat diet) induces obesity and metabolic disorders, which is associated with the alteration in gut microbiota profiles. However, the underlying molecular mechanisms of the processes are poorly understood. In this study, we used the simple model organism honey bee to explore how different amounts and types of dietary fats affect the host metabolism and the gut microbiota. Excess dietary fat, especially palm oil, elicited higher weight gain, lower survival rates, hyperglycemic, and fat accumulation in honey bees. However, microbiota-free honey bees reared on high-fat diets did not significantly change their phenotypes. Different fatty acid compositions in palm and soybean oil altered the lipid profiles of the honey bee body. Remarkably, dietary fats regulated lipid metabolism and immune-related gene expression at the transcriptional level. Gene set enrichment analysis showed that biological processes, including transcription factors, insulin secretion, and Toll and Imd signaling pathways, were significantly different in the gut of bees on different dietary fats. Moreover, a high-fat diet increased the relative abundance of Gilliamella, while the level of Bartonella was significantly decreased in palm oil groups. This study establishes a novel honey bee model of studying the crosstalk between dietary fat, gut microbiota, and host metabolism.

Dynamic remobilization of leaf nitrogen components in relation to photosynthetic rate during grain filling in maize.

Remobilization of leaf nitrogen (N) contributes greatly to grain N in maize, but leads to low photosynthetic rate (Pn). Pn is determined by various N components involving in light harvest and CO2 reduction. However, it is less clear which N component is the major contributor for the reduction of photosynthesis in modern stay-green maize hybrids. In this study, we analyzed the relationship between remobilization of different N components and Pn during grain filling stage under low N (no N application) and high N (180 kg N ha-1) in a field experiment. The remobilization efficiency of photosynthetic enzymes (PEPc, PPDK and Rubisco) in the leaf was much higher than that of thylakoid N and other N components. Low N supply increased the remobilization efficiency of all the leaf N components. During grain filling stage, the amount of all the N components decreased together with Pn. The ratio of Pn to the N in the PEPc, PPDK and Rubisco kept increase in the whole grain filling stage, while the ratio of Pn to chlorophyll and thylakoid-N decreased. Correlation analysis indicated that Pn was more related to the content of photosynthetic enzymes than to chlorophyll and thylakoid N. It is concluded that photosynthetic enzymes serve as an N storage reservoir at early grain filling stage and their degradation is critical in the reduction of Pn during later grain filling stage. Future breeding targets may be focused on enhancing the efficiency of photosynthetic enzymes during late grain filling stage.