# Adaptive Expression and ncRNA Regulation of Genes Related to Digestion and Metabolism in Stomach of Red Pandas during Suckling and Adult Periods

## TL;DR

This study explores how red pandas adapt their digestion and metabolism genes during different life stages, comparing them to ferrets, to understand their unique herbivorous diet evolution.

## Contribution

The study identifies novel ncRNA regulation and gene expression adaptations in red pandas related to dietary changes from milk to bamboo.

## Key findings

- Significant expression changes of 109 lncRNAs and 106 miRNAs in red pandas and 756 lncRNAs and 109 miRNAs in ferrets between suckling and adult periods were identified.
- Up-regulated genes related to amino acid transport in red pandas may help utilize limited bamboo amino acids, while up-regulated genes in ferrets may balance amino acid metabolism.
- Up-regulated lipid digestion genes in red pandas aid milk nutrient utilization, while linoleic acid metabolism genes in ferrets may reduce health risks.

## Abstract

Red pandas have evolved to become specialized bamboo eaters within Carnivora. Probably due to the difficulty in obtaining materials, reports on genes related to digestion and metabolism at expression and regulation levels in red pandas are rare. Red pandas and carnivorous mammal ferrets have a close phylogenetic relationship. They both consume highly nutritious milk during the suckling period, but consume low-energy bamboo and high-energy meat during the adult period, respectively. In order to explore the molecular mechanisms of dietary changes and nutrient utilization in red pandas, we discussed (1) the differences in expression changes of some genes related to digestion and metabolism in the stomach of these two species after food changes, as well as the expression adaptation of genes related to digestion and metabolism in both species during different feeding periods, and (2) the regulatory effects of lncRNAs and miRNAs on adaptive expressions of genes related to digestion and metabolism in both species from suckling to adult.

Red pandas evolved from carnivores to herbivores and are unique within Carnivora. Red pandas and carnivorous mammals consume milk during the suckling period, while they consume bamboo and meat during the adult period, respectively. Red pandas and carnivorous mammal ferrets have a close phylogenetic relationship. To further investigate the molecular mechanisms of dietary changes and nutrient utilization in red pandas from suckling to adult, comparative analysis of the whole transcriptome was performed on stomach tissues from red pandas and ferrets during the suckling and adult periods. The main results are as follows: (1) we identified ncRNAs for the first time in stomach tissues of both species, and found significant expression changes of 109 lncRNAs and 106 miRNAs in red pandas and 756 lncRNAs and 109 miRNAs in ferrets between the two periods; (2) up-regulated genes related to amino acid transport regulated by lncRNA-miRNA-mRNA networks may efficiently utilize limited bamboo amino acids in adult red pandas, while up-regulated genes related to amino acid degradation regulated by lncRNAs may maintain the balance of amino acid metabolism due to larger daily intakes in adult ferrets; and (3) some up-regulated genes related to lipid digestion may contribute to the utilization of rich nutrients in milk for the rapid growth and development of suckling red pandas, while up-regulated genes associated with linoleic acid metabolism regulated by lncRNA-miRNA-mRNA networks may promote cholesterol decomposition to reduce health risks for carnivorous adult ferrets. Collectively, our study offers evidence of gene expression adaptation and ncRNA regulation in response to specific dietary changes and nutrient utilization in red pandas during suckling and adult periods.