Gene Splice Helps Fight Crop Disease, Say Researchers
News Mar 15, 2010
Paris - Biologists on Sunday said they had found a potential superweapon in a long-running arms race with bacteria that threaten essential crops.
Tested in a lab, their technique entails inserting a gene kit into a plant so that its immune system recognises and fights germ invaders, they reported in the journal Nature Biotechnology.
Bacteria cause huge losses to crops each year. Farmers usually tackle the foe by dousing their fields with chemicals, but these are expensive and can damage soil biodiversity.
Another way is to shore up the plant's defences by a gene introduced through cross-breeding with a hardier strain. Yet this technique is rarely able to give a plant resistance against a wide range of germs -- and in any case a bacterium may swiftly evolve to sneak around the new defence.
Phytobiologists led by Cyril Zipfel at the Sainsbury Laboratory at Norwich, eastern England, took a novel tack. They delved into plants' innate defence system, hunting for watchdog genes able to spot a pattern of telltale proteins exuded by a microbial invader. Like bones and skin in humans, these proteins are essential for the bacteria's core functions and so are less likely to mutate, for to do so could harm the pathogen's survival.
The watchdog genes govern so-called pattern recognition receptors, or PRRs. PRRs were first discovered 15 years ago, although only a few have been discovered to date, and much is unclear. It was known that a PRR can spot essential proteins from quite a wide a range of bacteria. But it was uncertain whether the defence is unique to a given family of plants or can be transferred to another.
Exploring this avenue, Zipfel's team took a PRR that was specific to the Brassica family -- the plant group that includes mustard, Brussels sprouts and cabbage -- and slotted it into two plants from the Solanaceae family, which includes tomatoes, potatoes, aubergines (US: eggplants), tobacco and other valuable crops.
By having the PRR added to their arsenal, the Solanaceae plants showed "drastically enhanced" resistance to many different bacteria, including Ralstonia solanacearum, a major cause of crop wilt. "The strength of this resistance is because it has come from a different plant family, which the pathogen has not had any chance to adapt to," Zipfel said in a press release.