Helping Tomatoes Cope With Stress May Be Good For Us

Scientists at the John Innes Centre (JIC)and Institute of Food Research (IFR), Norwich, have today reported the discovery and use of a gene that may help protect plants and humans against disease. The gene (HQT) was identified in tomato and is responsible for producing an antioxidant called chlorogenic acid (CGA).

By increasing the activity of HQT, the scientists raised the levels of CGA in the tomato fruits and this helped protect them against attack from bacterial disease. CGA could also protect humans eating the tomatoes against degenerative, age-related diseases. This report is published online on 25 April in Nature Biotechnology and will be available in the June 2004 hard copy journal.

“Our tomatoes are doubly special” said Dr Cathie Martin (project leader at JIC). “They not only protect themselves against disease, but may benefit humans that eat them by protecting against age-related diseases. For us the excitement is that this adds to our understanding of how plants naturally protect themselves against stress and diseases, but in the long term it may be that this discovery leads to fruits that are better for us”.

The research team were interested in CGA because it is known to be an important antioxidant in both plants and animals. The biochemical pathway that plants use to make CGA was unknown, but a bit of biological detective work led the team to the likely pathway. When experiments confirmed their prediction, they were able to isolate one of the key genes (called HQT) for making CGA. When they suppressed the activity of the HQT gene (using gene silencing) they found that CGA levels in developing tomato fruits fell. The reverse happened when they increased the activity of HQT.

Antioxidants protect against the effects of stress and disease. To test whether higher levels of CGA give added protection the scientists infected the high CGA tomatoes with bacteria that cause tomato blight (Pseudomonas syringae). In the high CGA plants the effect and spread of the disease was significantly less than in the unmodified plants. Similarly, when the plants were tested for resistance to oxidative stress the high CGA plants were more resistant to stress damage than the unmodified plants.

“This research has highlighted for me the incredible ingenuity of plants in coping with their environment”, said Dr Tony Michael (Project Leader at IFR). “Plants possess a whole repertoire of genes involved in producing protective compounds. CGA is the main polyphenol in this category in tomatoes. Now we have identified the gene for the enzyme that produces it, we can look for genes that produce similar compounds in other plants, with benefits for agriculture and for human nutrition”.

The Intellectual Property Rights associated with this discovery are assigned to Plant Bioscience Ltd.