Representative 2-DE images of proteins extracted from dairy goat liver.

<p>A) Control group; B) High-grain diet group. Equal amounts of protein (850 µg) were loaded and separated on 17-cm IPG strips (pH 3–10), followed by electrophoresis on 12.5% SDS-PAGE gels for second dimension electrophoresis. The gels were stained with CCB G250. Experiments were performed in triplicate.</p

Gene ontology (GO) analysis of differentially expressed proteins.

<p>GO annotations are presented by category: A) biological process B) cellular components C) molecular function.</p

KEGG pathway analysis of differentially expressed proteins.

<p>Pathway enrichment analysis was performed using the DAVID web application.</p

2-DE patterns of proteins extracted from dairy goat liver.

<p>A. Control group; B. High-grain diet group. Fifty-two differentially expressed proteins showing significant spot intensity changes are marked in A and B. The proteins to which these 52 differentially expressed protein spots correspond are listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080698#pone-0080698-t002" target="_blank">Table 2</a>.</p

Identification of differentially expressed liver proteins.

a<p>Numbering corresponds to the 2-DE gel in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080698#pone-0080698-g001" target="_blank">Fig.1</a>.</p>b<p>The total number of identified peptide.</p>c<p>Increased(>) or decreased(<) compared with the control group.</p

The primer sequences used for quantitative qRT-PCR of the differentially expressed genes related to diet type.

<p>The primer sequences used for quantitative qRT-PCR of the differentially expressed genes related to diet type.</p

Western blot analysis of calreticulin (CALR; A) and apolipoprotein A-I (ApoA-I; B) in liver tissue samples from high-grain diet and control groups.

<p>Protein extracts of liver tissue samples were prepared and subjected to immunodetection with the indicated antibodies. Intensities of CALR and ApoA-I bands were normalized to the corresponding β-actin control. Values are presented as means ± SD; n = 5. * <i>P</i><0.05.</p

Possible energy metabolism in duck.

<p>The symbols “↑” and “↓” indicate the protein up- or down-regulation response to heat stress. Species-specific changes are indicated as M (Muscovy) or PK (Pekin duck). <b>Abbreviations: UDPG</b>, UDP-glucose; <b>Gn</b>, glycogen; <b>G3P</b>, glyceraldehyde-3-phosphate; <b>3-PG</b>, 3-phosphoglycerate; <b>PEP</b>, phosphoenolpyruvate; <b>CoA</b>, coenzyme A; <b>ETC</b>, electron transport chain.</p

Comparative Proteomic Analysis of the Hepatic Response to Heat Stress in Muscovy and Pekin Ducks: Insight into Thermal Tolerance Related to Energy Metabolism

<div><p>The Pekin duck, bred from the mallard (<i>Anas platyrhynchos</i>) in china, is one of the most famous meat duck species in the world. However, it is more sensitive to heat stress than Muscovy duck, which is believed to have originated in South America. With temperature raising, mortality, laying performance, and meat quality of the Pekin duck are severely affected. This study aims to uncover the temperature-dependent proteins of two duck species using comparative proteomic approach. Duck was cultured under 39°C ± 0.5°C for 1 h, and then immediately returned to 20°C for a 3 h recovery period, the liver proteins were extracted and electrophoresed in two-dimensional mode. After analysis of gel images, 61 differentially expressed proteins were detected, 54 were clearly identified by MALDI TOF/TOF MS. Of the 54 differentially expressed protein spots identified, 7 were found in both species, whereas 47 were species specific (25 in Muscovy duck and 22 in Pekin duck). As is well known, chaperone proteins, such as heat shock protein (HSP) 70 and HSP10, were abundantly up-regulated in both species in response to heat stress. However, we also found that several proteins, such as α-enolase, and <i>S</i>-adenosylmethionine synthetase, showed different expression patterns in the 2 duck species. The enriched biological processes were grouped into 3 main categories according to gene ontology analysis: cell death and apoptosis (20.93%), amino acid metabolism (13.95%) and oxidation reduction (20.93%). The mRNA levels of several differentially expressed protein were investigated by real-time RT-PCR. To our knowledge, this study is the first to provide insights into the differential expression of proteins following heat stress in ducks and enables better understanding of possible heat stress response mechanisms in animals.</p> </div

Representative spot maps of M (Muscovy) and PK (Pekin duck).

<p><b>HT</b> stands for heat treated and <b>RC</b> stands for recovery after heat stress. Equal amounts of protein (850 µg) were loaded and separated on 17 cm IPG strips (PH 3-10), followed by electrophoresis on 12.5% SDS-PAGE gels for second dimension electrophoresis. The gels were stained with CCB G250.</p