Camels: excellent examples of biotic resistance against salt load and drought

Animals face severe challenges when they live in areas of high salinity and aridity, however, adaptive evolution can improve this situation over a long period of time. Camels are a typical example of an animal that is well-adapted to their extreme habitats, thanks to natural selection which ensures that only the fittest survive and can therefore pass their genes on to the next generation. The Inner Mongolia Key Laboratory of Bio-manufacture, established in Inner Mongolia Agricultural University, has precisely explained how camels exert the salt and drought resistances at molecular level, and is involved in finding safer approaches to apply the clarified mechanisms to modern practice of breeding livestock.

Extreme circumstances are one of the chief hindrances for the existence and reproduction of the animals, but also lead to creatures that have adapted to cope with incredibly difficult environments. High-salt conditions can trigger inflammation and a disequilibrium in neurotransmitters in the paraventricular nucleus in the body. The effects of malnutrition, such as physical wasting or stunting, are a widespread health concern brought on by drought conditions. These conditions can lead to death in large animals, and is one of key reasons why certain species migrate. It is no surprise that animals, such as camels, which live in these conditions have special metabolic pathways that are regulated via genes based on evolutional selection, having adapted to their harsh natural environments.

 

Camels, which are occasionally known as the ‘ship of the desert’, are desert-dwelling mammals, with the infamous capacity to adapt to incredible levels of salinity, and perennially parched environments. The camel’s renal system is well-adapted to deal with increased sodium excretion and is able to remove excessive salt. The oval red blood cells and their quick transition can protect red blood cells from bursting as a result of high osmotic variation, which is a risk due to the fact that camels drink large quantities of water at a time. In comparison to other livestock, camels show lower water loss during periods of drought as they are able to produce more concentrated urine and dry faeces, thus averting unnecessary water loss.

 

The Inner Mongolia Key Laboratory of Bio-manufacture team at Inner Mongolia Agricultural University sheds light on the naturally selected genes of camels against high salt and water deficit stresses through multi-organic omics investigation. Changes of the gene expression lead to incredible benefits, such as:

    1. Reducing sodium-dependent transporters and prevent cell dehydration from citrate cycle in the camel’s renal system,
    2.  Avoiding excessive sodium ion import in an exchanger-dependent manner prodded by mucin secretion and ensure high energy reserve, rapid energy buffer and osmotic homeostasis in camel ileum,
    3. Constructing a defensive membrane barrier to sodium ion flux, and diverting uridine to functional restoration in camel livers.

 

Further adaptations in resistant characteristics, such as the slowing down of aerobic respiration and metabolism, alongside improved antioxidative capability, are also encouraged by the preferential genes. Notably, the evolutional gene expression pattern involves the transcription process of pre-translation of protein-coding gene that are regulated by non-coding RNAs, such as microRNA and long non-coding RNA. These are generally interpreted as RNA molecules which do not translate into proteins, and were once regarded as transcriptional noises arising from so-called ‘junk DNA’. Now the team members are challenging traditional breeding methods, and seeking a high-level biosafe way of introducing these genes into other livestock, allowing them to manage saline load and water shortage conditions by means of these identified molecules and mechanisms.

References
[1]. Zhang, D., Pan, J., Cao, J., Cao, Y. and Zhou, H., 2020. Screening of drought-resistance related genes and analysis of promising regulatory pathway in camel renal medulla. Genomics, 112(3), pp. 2633-2639. [2]. Zhang, D., Pan, J., Zhou, H. and Cao, Y., 2020. Evidence from ileum and liver transcriptomes of resistance to high-salt and water-deprivation conditions in camel. Zoological Letters, 6, p. 8. [3]. Cao, Y., Zhang, D. and Zhou, H., 2019. Key genes differential expressions and pathway involved in salt and water-deprivation stresses for renal cortex in camel. BMC Molecular Biology, 20(1), p. 11.

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