Abstract
BackgroundEgg formation takes place in the oviduct of laying hens over a 24 h period. Infectious bronchitis virus (IBV) causes pathological lesions in the chicken oviduct. In the current study, mitochondrial counts were determined in three different segments of the oviduct during egg formation in laying chickens challenged with IBV T strain. Nuclear DNA encoded genes that are involved in mitochondrial biogenesis, fission and function were studied in the shell gland of the oviduct undergoing virus multiplication.ResultsIn the shell gland, the mitochondrial count was significantly lower (P < 0.05) in the challenged group, compared with the control group. However, it did not vary in response to IBV challenge in the isthmus and magnum regions of the oviduct. The gene succinate dehydrogenase complex, subunit A, flavoprotein variant (SDHA) was down-regulated in the shell gland by IBV challenge (P < 0.05), while other genes being studied did not show responses to the challenge (P > 0.05). Differential expression of the genes was observed at different time-points of egg-shell formation. The expression levels of citrate synthase (CS), cytochrome C, somatic (CYC, S) and sodium-potassium adenosine triphosphatase (Na+-K+ATPase) genes were significantly higher, while those of SDHA and dynamin related protein 1 (Drp1) genes were significantly lower, at 15 h compared with 5 h following oviposition of the previous egg. The expression level of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) did not show significant change at different time-points.ConclusionsIt was concluded that IBV T strain infection in laying hens reduced mitochondrial counts only in the shell gland region of the oviduct. The genes involved in mitochondrial biogenesis or function may not show synchronised responses to that of mitochondria in the shell gland of chickens under T strain of IBV challenge.
Highlights
Egg formation takes place in the oviduct of laying hens over a 24 h period
We investigated the mitochondrial counts in three different segments of the oviduct of laying hens challenged with Infectious bronchitis virus (IBV) T strain, at two stages of egg formation
Based on the lack of significant differences in mitochondrial count in the cells between the challenged and control groups for the magnum and isthmus, we focused further on shell gland tissue and studied the expression level of genes involved in mitochondrial density, biogenesis and fission
Summary
Egg formation takes place in the oviduct of laying hens over a 24 h period. Mitochondrial counts were determined in three different segments of the oviduct during egg formation in laying chickens challenged with IBV T strain. The infundibulum, magnum, isthmus and shell gland (uterus) contribute to egg formation in laying chickens. Egg-shell formation takes place in the isthmus and shell gland regions, where the former contributes only to shell membrane formation. Albumen is secreted by the magnum and is composed mainly of ovalbumin, muco-proteins and globulins [4]. The shell membranes are synthesized in the isthmus region of the oviduct and contain collagen proteins in its composition [5]. Egg-shell synthesis occurs in the shell gland and is composed mainly of calcium carbonate [6] and shell matrix proteins, such as the ovocalyxin family [5]
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