Genomics unlocks key to Mendel's pea flowers

John Innes Centre scientists have helped discover the key to one of biology's most well-known experiments - the gene that controls pea flower colour, used by Gregor Mendel in his initial studies of inheritance. 150 years ago Gregor Mendel planted peas segregating for flower colour. Now an international group of scientists, publishing in the journal PLoS-ONE, has revealed the underlying molecular genetics behind this experiment, identifying genes that control flower colour in pea plants. Peas have been used to study inheritance and genetics for hundreds of years, from the eighteenth century investigations into inheritance, through Gregor Mendel's celebrated experiments, to developing improved pea varieties. "Mendel is known as the father of modern genetics, using pea characteristics to demonstrate inheritance patterns," says Dr Roger Hellens, Science Leader of the Genomics Group at Plant & Food Research, New Zealand. The purple colour of wild type pea flowers, and flowers of many other plants, is a consequence of the accumulation of pigment molecules called anthocyanins and the biochemistry of their production has been studied for many years. The paper describes two pea genes, known as A and A2, that regulate the production of anthocyanins. The work was a collaboration between scientists at the John Innes Centre, an institute of BBSRC, New Zealand's Plant & Food Research, URGV in France and the USDA's Agricultural Research Services. "This was a real collaborative effort, it would not have happened without all of these people participating, especially if Roger had not had the enthusiasm to nail a problem that has been bugging him for years," says Professor Noel Ellis, of the Department of Crop Genetics at the John Innes Centre. "By comparing the pea DNA sequences to those of other well-characterised plants, such as petunia, we have determined that Mendel's gene is a transcription factor that controls the anthocyanin biosynthesis pathway. This transcription factor, when mutated, becomes inactive and anthocyanin is not produced, resulting in white flowers," says Dr Hellens. The John Innes Centre houses a collection of around 3,500 pea lines that was used in this study. The collection includes material from wild, cultivated and semi-cultivated sources, some dating back to the nineteenth century. This germplasm collection is a valuable genetic resource for scientists and plant breeders looking for improved pea varieties. "We used information from our previous genotyping of the JIC pea germplasm collection to identify exotic lines where we would most likely find rare alleles of Mendel's gene. Finding a rare second allele was important for independent confirmation of the identity of the gene," says Prof. Ellis. "This is the fourth of Mendel's seven genes to be characterised at the molecular level: it is also the second where JIC has been involved." The John Innes Centre is now looking into the germplasm collection for genes and traits that could be used to make peas higher-yielding or of better quality. Peas are able to fix nitrogen from the air through symbiotic relationships with bacteria housed in nodules in their roots. This makes them less dependent on the addition of nitrogenous fertilisers which are a major economic and environmental cost associated with farming because they require high levels of energy for their production and their use is a major source of nitrous oxide, a potent greenhouse gas. The increased production of peas and other legumes is a good way of ensuring future food security with low environmental cost. Funding was received from Defra and the EU FP6 Grain Legumes Integrated Project, the New Zealand Foundation for Research Science and Technology and BBSRC. ENDS Notes to editors Reference: "Identification of Mendel's white flower character" will be published in PLoS ONE on Monday, October 11 2010. http://dx.plos.org/10.1371/journal.pone.0013230