罢丑别谤别鈥檚 more to inbreeding than dubious genes 鈥� how they are 鈥渞ead鈥� matters, too. If a key influence on gene expression is blocked, inbred plants show few signs of their incestuous heritage. The finding may one day help small populations of endangered species breed healthily.
Many organisms carry two copies of each gene, with one member of the pair being dominant. This means individuals can carry a potentially harmful gene whose effect is masked by its normal partner. When two closely related individuals breed, however, their offspring may inherit two copies of the bad gene 鈥� one from each parent 鈥� and suffer its ill effects, a phenomenon called inbreeding depression.
and her colleagues at Radboud University in Nijmegen, the Netherlands, have discovered that there may be more to the consequences of inbreeding than these genetic doppelgangers.
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Inbred but healthy
The team collected wild seed from a common perennial () and grew it in the lab. After the plants flowered, the researchers self-pollinated some plants and cross-pollinated others to create inbred and outbred siblings.
Grown under standard conditions, the inbred plants had fewer leaves and less biomass than those that had been outbred. But the team managed to counter these ill effects without altering the plants鈥� genetic code.
The inbred seeds developed fairly normally if soaked in a solution that stops methyl chemical groups from clamping to DNA. DNA methylation is a kind of 鈥渆pigenetic modification鈥�, affecting how genes are read, and may be triggered by environmental factors.
鈥淭his is the kind of data we have been waiting years for,鈥� says at the University of Lyon, France, who suggested decades ago that inbreeding鈥檚 effects go beyond the genome. 鈥淎t the time we did not have the techniques to test such hypotheses.鈥�
Save our species
, a conservation geneticist at Macquarie University in Sydney, Australia, says some epigenetic influence comes as no great surprise. 鈥淗owever, to find that reversing epigenetic effects by chemical treatment completely eliminated inbreeding depression is extremely surprising.鈥�
Many endangered species are inbred. The new study suggests they might reproduce normally with epigenetic treatment.
at the University of Edinburgh, UK, says there are issues to be overcome, though. 鈥淚t is very important to be clear what one means by 鈥榓n epigenetic role鈥�,鈥� she says. 鈥淭urning genes off and on in development is absolutely distinct from suggesting that these effects are transmitted to the next generation, let alone to future generations鈥� 鈥� something that Vergeer鈥檚 team has not yet observed.
鈥淚t is important not to get ahead of ourselves and assume that we can stop worrying about inbreeding depression,鈥� says Frankham. 鈥淚f the 鈥榗uring鈥� effects are lost in the next generation, then the work provides interesting background, but it has very little or no practical application.鈥�
鈥淲e are testing this inheritance at the moment,鈥� says Vergeer. 鈥淪ince heritability of epigenetic modifications has been shown for a number of species, I believe that in general these epigenetic changes in inbreeding depression can play a large role in evolution.鈥�
Journal reference: , DOI: 10.1098/rsbl.2012.0494
