This is breaking news. Scientists have decoded the genomes of two types of snakes , the cobra and python. These results are published in two separate papers in the recent issue of Proceedings of the National Academy of Sciences, U.S.A. (1,2) Both teams were seeking an "evolutionary" answer to the peculiar eating habits of these snakes. How did one group develop poisonous venom to kill the prey and the other acquire enough muscle power to swallow the prey?
According to the tree of Life the common ancestor of all snakes is the lizard. One school of thought is that when circumstances forced the lizards to live in water, evolution shaved off their legs to turn them into more efficient swimmers. Another group is the of the opinion that at some point perhaps due to adverse climatic conditions, lizards had to take shelter underground and thus burrowing sawed off the legs. The verdict is not yet out, but scales could be tilting a bit in favor of burrowing, because of Najash the Fossil. This fossil of a 90 million year old burrowing snake sports a pair of hind legs. Well, getting back to the cobra- python story perhaps there is a clue in the comparative body sizes of the snake and its prey; small agile snakes developed the venomous route to shock and kill their small prey while big snake like the python relied more on its own muscle power to subdue bigger prey.
Vonk et al set out to understand the molecular biology of cobra venom. Venom is a concoction of toxic peptides. Which genes code for these peptides? Perhaps that will yield an evolutionary clue? They sequenced the genome of the king cobra and linked the toxic peptides to about 20 odd genes. They found that the venomous pathway has a pancreatic origin. They also hint at the possibility that the potency of the venom must have increased over a period of time to compete with the prey's ever alert defense mechanisms. Surprisingly the research team found nothing extraordinary in the genes for specific toxins. These were genes that coded for peptides used for other bodily functions elsewhere, such as blood clotting or BP lowering...etc. But what intrigued them was the presence of multiple copies of these genes; perhaps ready for easy and potent mutations. Decoding the genes for venom is a great help to the pharmaceutical field where, be it from any source, venom is worth its weight in gold. Because venom could hold secret formula for a variety of drugs. Several cardiovascular and CNS drugs are modeled on peptides found in snake venom which exhibit similar behaviour(3). In France, scientist Pierre Escoubas has ventured to establish a company VenomeTech "to lead the development of new drugs in the area of of pain cancer and diseases of the central nervous system", as the company's website proclaims.
The story is slightly different in the case of pythons. Pythons can starve for months at a stretch. But then when they get to eat a sumptuous meal, their internal organs balloon to accommodate the prey and metabolic rate multiplies several fold . How does this happen? Castoe's team discovered "massive rapid changes in the gene expression that coordinate major changes in the organ size and function after feeding;" corresponding genes in humans perform rather insipid jobs in the area of metabolism, development and pathology. Castoe and his team went one step ahead and compared the genomes of the python and the Cobra. They found 7442 genes common for both as well as other vertebrates. They suggest that snake genomes have differentiated and evolved much faster in response to the peculiar constraints they encounter.
That brings us to a curious question. Does that mean cobras and pythons have reached the plateau of their respective evolutionary process? Like as some scientists assume Humans are the ultimate intelligent beings ? Far from it. Prof. Richard Lenski at Michigan State University, USA has been studying the evolutionary saga of Escherichia coli for the past two and a half decades. His experiments demonstrate that evolution never stops; Oh yes, it might accelerate or slow down , but never stops even in an unchanging environment .
1. The king Cobra genome reveals dynamic gene evolution and adaptation in snake venom systems: Vonk et al PNAS 110 (51) pages 20651-20656, 2013
2. The Burmese python genome reveals the molecular basis for extreme adaptation in snakes. Castoe et al PNAS 110(51) 20645-2065, 2013.
3. From toxins to treatment- Kupferschmidt, Science 342, 1162-1164, 6 Dec. 2013
4.The Man who bottled evolution : Elizabeth Pennisi, Science 342 , 790-793, 15 Nov. 2013
According to the tree of Life the common ancestor of all snakes is the lizard. One school of thought is that when circumstances forced the lizards to live in water, evolution shaved off their legs to turn them into more efficient swimmers. Another group is the of the opinion that at some point perhaps due to adverse climatic conditions, lizards had to take shelter underground and thus burrowing sawed off the legs. The verdict is not yet out, but scales could be tilting a bit in favor of burrowing, because of Najash the Fossil. This fossil of a 90 million year old burrowing snake sports a pair of hind legs. Well, getting back to the cobra- python story perhaps there is a clue in the comparative body sizes of the snake and its prey; small agile snakes developed the venomous route to shock and kill their small prey while big snake like the python relied more on its own muscle power to subdue bigger prey.
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| Tree of Life by German Scientist Ernst Haeckel in the Evolution of Man 1879 Courtsey : English Wikipedia Tree of life (Biology) |
Vonk et al set out to understand the molecular biology of cobra venom. Venom is a concoction of toxic peptides. Which genes code for these peptides? Perhaps that will yield an evolutionary clue? They sequenced the genome of the king cobra and linked the toxic peptides to about 20 odd genes. They found that the venomous pathway has a pancreatic origin. They also hint at the possibility that the potency of the venom must have increased over a period of time to compete with the prey's ever alert defense mechanisms. Surprisingly the research team found nothing extraordinary in the genes for specific toxins. These were genes that coded for peptides used for other bodily functions elsewhere, such as blood clotting or BP lowering...etc. But what intrigued them was the presence of multiple copies of these genes; perhaps ready for easy and potent mutations. Decoding the genes for venom is a great help to the pharmaceutical field where, be it from any source, venom is worth its weight in gold. Because venom could hold secret formula for a variety of drugs. Several cardiovascular and CNS drugs are modeled on peptides found in snake venom which exhibit similar behaviour(3). In France, scientist Pierre Escoubas has ventured to establish a company VenomeTech "to lead the development of new drugs in the area of of pain cancer and diseases of the central nervous system", as the company's website proclaims.
The story is slightly different in the case of pythons. Pythons can starve for months at a stretch. But then when they get to eat a sumptuous meal, their internal organs balloon to accommodate the prey and metabolic rate multiplies several fold . How does this happen? Castoe's team discovered "massive rapid changes in the gene expression that coordinate major changes in the organ size and function after feeding;" corresponding genes in humans perform rather insipid jobs in the area of metabolism, development and pathology. Castoe and his team went one step ahead and compared the genomes of the python and the Cobra. They found 7442 genes common for both as well as other vertebrates. They suggest that snake genomes have differentiated and evolved much faster in response to the peculiar constraints they encounter.
That brings us to a curious question. Does that mean cobras and pythons have reached the plateau of their respective evolutionary process? Like as some scientists assume Humans are the ultimate intelligent beings ? Far from it. Prof. Richard Lenski at Michigan State University, USA has been studying the evolutionary saga of Escherichia coli for the past two and a half decades. His experiments demonstrate that evolution never stops; Oh yes, it might accelerate or slow down , but never stops even in an unchanging environment .
1. The king Cobra genome reveals dynamic gene evolution and adaptation in snake venom systems: Vonk et al PNAS 110 (51) pages 20651-20656, 2013
2. The Burmese python genome reveals the molecular basis for extreme adaptation in snakes. Castoe et al PNAS 110(51) 20645-2065, 2013.
3. From toxins to treatment- Kupferschmidt, Science 342, 1162-1164, 6 Dec. 2013
4.The Man who bottled evolution : Elizabeth Pennisi, Science 342 , 790-793, 15 Nov. 2013
