Some of the secrets behind the emergence of new species have been uncovered in a genetic study, conducted in collaboration with bioscientists at The University of Nottingham.
Almost all plant species are known to have cross-breeds that sometimes produce infertile offspring. Now for the first time the team, led by the French National Institute for Agricultural Research, INRA-Versailles, has identified a simple genetic mechanism that may explain why this happens. The results have been published in the journal Science.
Professor Malcolm Bennett, Biology Director for the Centre for Plant Integrative Biology and Head of Division of Plant and Crop Sciences at The University of Nottingham said: “As plants evolve, their genes may get copied, moved around the genome, and inactivated. This will reduce the possibilities for fertile cross-breeds and, over time, may result in the emergence of distinct species. We’re delighted that this study demonstrates this process in action.”
The study explains why the offspring of some cross-breeds are not viable and indicates a potential mechanism for the formation of sub-species in supposedly identical populations.
The researchers, specialists in the genetics of the model plant Arabidopsis thaliana, first noted that
offspring of the cross between two of the plant's natural strains, Columbia (Col) and Cape Verde Island (Cvi), did not fully obey Mendel's Laws of Inheritance. Researchers found that in specific genetic combinations of two parent genomes, some did not produce offspring at all.
Further investigation showed that a gene called HPA is carried by chromosome 1 in the Cvi strain, but in the Col strain a second copy is also found on chromosome 5. As the Col strain evolved, the copy of HPA on chromosome 1 became inactive. As a result, the two strains of Arabidopsis now have their functional HPA genes on different chromosomes. The HPA gene is responsible for the production of histidine, an essential amino acid that is necessary for reproduction to take place.
Embryos that inherit one inactive HPA gene from chromosome 1 of a Cvi parent and another from chromosome 5 of a Col parent cannot produce histidine and fail to develop.
If the gene isn’t present the two different strains become incompatible, making it impossible for parent plants to produce offspring. Researchers were able to confirm this after observing that plants watered with a histidine solution were able to produce embryos that developed normally.
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Notes to editors
Image of plant seedling used courtesy of Dr Andy French, Dr Hannah Edwards, Dr Darren Wells, Dr Tara Holman at The University of Nottingham.
The University of Nottingham is ranked in the UK's Top 10 and the World's Top 100 universities by the Shanghai Jiao Tong (SJTU) and Times Higher (THE) World University Rankings.
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The University provides innovative and top quality teaching, undertakes world-changing research, and attracts talented staff and students from 150 nations. Described by The Times as Britain's "only truly global university", it has invested continuously in award-winning campuses in the United Kingdom, China and Malaysia. Twice since 2003 its research and teaching academics have won Nobel Prizes. The University has won the Queen's Award for Enterprise in both 2006 (International Trade) and 2007 (Innovation — School of Pharmacy), and was named ‘Entrepreneurial University of the Year’ at the Times Higher Education Awards 2008.
The Centre for Plant Integrative Biology (CPIB) is funded by the Systems Biology joint initiative of BBSRC and EPSRC, which has provided £27M for six specialised centres across the UK. The Division of Plant and Crop Sciences is one of the largest communities of plant scientists in the UK. Around 160 people work in the Division, which welcomes visiting scientists from all over the world, reinforcing its reputation as a world renowned centre.