A genomics-informed, SNP association study reveals FBLN1 and FABP4 as contributing to resistance to fleece rot in Australian Merino sheep

The majority of the DE genes originated from the fleece rot subtracted libraries and over-representing gene ontology terms included defense response to bacterium and epidermis development, indicating a role of these processes in modulating the sheep's response to fleece rot. We focused on genes that contribute to the physical barrier function of skin, including keratins, collagens, fibulin and lipid proteins, to identify SNPs that were associated to fleece rot scores.We identified FBLN1 (fibulin) and FABP4 (fatty acid binding protein 4) as key factors in sheep's resistance to fleece rot. Validation of these markers in other populations could lead to vital tests for marker assisted selection that will ultimately increase the natural fleece rot resistance of Merino sheep.Fleece rot (FR) is a bacterial dermatitis of the sheep skin and fleece caused by an overgrowth of the natural skin microflora following prolonged exposure to moisture [1,2]. FR is characterised grossly by bands of matted and often discoloured fibres along the mid-line of the animal over the neck, wither, mid-back and rump regions. Its severity ranges from bacterial discoloration causing coloured bands (water stain), to extensive gummy exudates (wool rot) causing bands of matted fibres [3]. Severe FR can cause weakening of wool substantially lowering wool quality and value. In addition to direct effects on fleece quality, FR is the most important predisposing factor to blowfly body strike, a form of blowfly strike, in eastern Australia. Inflammation and ulceration of the skin occurs at the FR affected site attracting blowflies which deposit eggs and providing moisture for the eggs to hatch and soluble protein for the freshly hatched larvae to feed on which can lead to severe tissue damage and death in extreme cases. Body strike causes significant losses annually as a result of increased chemical and labour costs and reduced production.Three host barriers have been identified that are involved in the de