Comparative Quantitative Analysis of Gene Expression Profiles of Glycoside Hydrolase Family 10 Xylanases in the Sheep Rumen during a Feeding Cycle

Abstract

Xylanase is a crucial hydrolytic enzyme that degrades plant polysaccharides in the rumen. To date, there is no information on the genetic composition and expression characteristics of ruminal xylanase during feeding cycles of ruminants. Here, the major xylanase of the glycoside hydrolase family 10 (GH 10) from the rumen of small-tail Han sheep was investigated during a feeding cycle. We identified 44 distinct GH 10 xylanase gene fragments at both the genomic and transcriptional levels. Comparison of their relative abundance showed that results from the evaluation of functional genes at the transcriptional level are more reliable indicators for understanding fluctuations in xylanase levels. The expression patterns of six xylanase genes, detected at all time points of the feeding cycle, were investigated; we observed a complex trend of gene expression over 24 h, revealing the dynamic expression of xylanases in the rumen. Further correlation analysis indicated that the rumen is a dynamic ecosystem where the transcript profiles of xylanase genes are closely related to ruminal conditions, especially rumen pH and bacterial population. Given the huge diversity and changing composition of enzymes over the entire rumen, this research provides valuable information for understanding the role of functional genes in the digestion of plant material.

A C-Terminal Proline-Rich Sequence Simultaneously Broadens the Optimal Temperature and pH Ranges and Improves the Catalytic Efficiency of Glycosyl Hydrolase Family 10 Ruminal Xylanases

“…Because xylan degradation by xylanase is the first step taken to break down the lignocellulose in feedstuff, a xylanase with high catalytic performance is more favorable for feedstuff utilization. In our previous study of xylanase expression in sheep rumen, xynA was found to represent the most predominantly expressed xylanase gene of GH10 (15). We conjecture that XynA has certain favorable characteristics over others in the highly competitive rumen environment.…”

“…Yang et al (36) fused an oligopeptide to the N terminus of an ␣-amylase and improved its catalytic efficiency, thermal stability, and resistance to oxidation. In this study, we fused the proline-rich sequence of XynA to the C terminus of another ruminal xylanase (XynB) of the same source and the same family (15). The fused protein showed an improved catalytic efficiency of 27-fold and more complete hydrolysis products, mainly xylose and xylobiose.…”

“…We previously studied the expression pattern of GH10 xylanases in sheep rumen during a feeding cycle and found that a few genes were predominant during the entire process (15). Of these, xynA was determined by real-time quantitative PCR to be the most highly transcribed xylanase gene.…”

Genetic diversity and expression profiles of cysteine phytases in the sheep rumen during a feeding cycle

“…Our previous study has shown that, during a 24‐h feeding cycle, the bacterial population in sheep rumen fluid kept increasing, reached the maximum at 12 h and then decreased in the next 12 h slowly (Li et al . ). In this changing environment, ruminal microbes are likely to produce functional enzymes with different pH preferences.…”

‘Omics’ Approaches to Understand and Manipulate Rumen Microbial Function

“…They found 32 genera that were common in all samples but exhibit high variability in abundance across samples. In another approach, Li et al ( 2013 ) studied the expression profi le of the major xylanase of the glycoside hydrolase family 10 (GH 10) from the rumen samples at the time of feeding cycles of a small-tail Han sheep. Evidence of the presence of 44 distinct GH 10 xylanase gene fragments at both the genomic and transcriptional levels was found.…”