Characterisation of white and black merino wools: a proteomics study

Wool is an important agricultural commodity. The finest quality wool is produced by merino sheep and over the last 200 years most of this has been obtained from white merino breeds. Nevertheless, although sheep with pigmented wool are extremely rare, the market for it is increasing in specific niche areas. In Portugal there are two breeds, the white and the black merino, both descendants of the original animals long-developed in the Iberian Peninsula. These breeds have the potential to assist in our understanding of how protein expression relates to wool traits of importance to the textile industry. Herein, we study the protein expression profiles of wool from ewes of the Portuguese black and white merino breeds using an iTRAQ based approach to determine how they relate to the basic traits of both types of wool (diameter and curvature). Both breeds had very similar results for fibre diameter (25 microns) and curvature (105-111 degrees/mm). Significant differences were found between breeds with HSP (high sulfur proteins) and HGTP (high glycine tyrosine proteins). The HSPs, KAP2-3 and KAP2-4 had a decreased expression in the pigmented animals, whereas KAP13-1 was found in higher amounts. Likewise the ultra-high sulfur proteins, KAP4-3 and KAP4-7-like were reduced in black sheep to half the levels of the white wools, while the HGTPs KAP6, KAP6-1, KAP6-2 and KAP16-2 all exhibited significant increases in the black sheep. These results indicate the existence of specific differences between black and white wool, related to their site of expression site, the orthocortex and paracortex, and suggested structural differences between the two breeds.