http://www.smh.com.au/world/coffee-developed-caffeine-independently-from-its-cousin-cacao-study-20140905-10cvgp.html
Coffee developed caffeine independently from its cousin cacao: study
Scientists have unveiled the genome of the coffee plant.
Los Angeles: Researchers have pieced together the genetic atlas of the two most commonly cultivated species of coffee plant and uncovered a rather independent streak in their evolution.
Coffee developed its caffeine-generating capacity independently from its cousin, cacao, according to the first whole genome study published online in the journal Science.
The international team that spent years piecing together coffee's genome suggests that the capacity to produce caffeine has developed independently at least twice, in cacao and coffee, in what's known as convergent evolution. (Koalas and humans, for instance, have fingerprints, and widely divergent animals have developed prickly outsides to protect their gooey insides.)
Scientists used crushed stems, leaves and flower parts to assemble the genome.
Compared with its close relatives and ancestors, coffee harbours larger families of the genes linked to aroma and bitterness and has a wider array of genes linked to caffeine production, the study found.
How those new genes popped up and proliferated appears to be a series of small, fortuitous accidents, the study suggests. Neighbouring genes were duplicated by a process roughly equivalent to erratic coding and processing in a computer. Unlike computers, biological systems are ruthless housekeepers, shucking duplicates like excess baggage. Sometimes duplicates develop their own specialty, which appears to be what happened in the case of coffee, the authors suggest.
"A small percentage of them survive, either by splitting functions or evolving new ones," said study co-author Victor Albert, an evolutionary biologist at the University at Buffalo, part of the State University of New York. "In the case of caffeine genes, we have a series of duplications that occurred all next to each other, which gave rise to enzymes that catalyse different steps" in caffeine production.
Evolution favoured caffeinated plants because caffeine repels insects that prey on its leaves and halts the germination of seeds from competing plants, giving the plant a niche in which to thrive. Recent research also has suggested caffeine can help orient beneficial pollinators toward the coffee flower, Dr Albert said.
Duplication of an entire genome is thought to be the driving force in the rise of new species and wide diversification of life. But coffee appears to have taken the slower, piecemeal approach of small duplications. That could mean biologists have been underestimating its relative importance, Dr Albert said.
The largely French team used crushed stems, leaves and flower parts from Coffea canephora and its hybrid offspring, Coffea arabica, to assemble the genome, which consists of 710 million building blocks.
Los Angeles Times
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