Bacteria, plants communicate

An eccentric Dr Dolittle once claimed he could ''talk to the animals'', but University of Otago researcher Prof Clive Ronson has helped show bacteria actually do communicate with plants, including white clover.

Prof Ronson, of the Otago microbiology and immunology department, is part of an international collaborative study that has just been published in the international journal Nature.

This sheds new light on communication between different species, and how carbohydrates are used as signal molecules.

Prof Ronson is ''very excited'' by the findings, which are ''a highlight'' of his career, and also involve a research team led by Prof Jens Stougaard in Denmark, at the Centre for Carbohydrate Recognition and Signalling.

Clover and other legumes form unique symbiotic relationships with bacteria called rhizobia, which they allow to infect their roots. Root nodules are then formed in which the bacteria convert nitrogen from the air into ammonia, boosting plant growth.

Prof Ronson said white clover, a key pasture plant, also used a kind of ''dress code'' to screen bacteria seeking entry to the roots.

The plant recognised the favourable bacteria through ''exopolysaccharides''- sugar residues on their outer surface- and let those bacteria enter.

The same checking of external ''dress'' was also used to exclude unwanted micro-organisms, including bacteria that could prove damaging.

The plants were ''simply closing the door''.

''If you don't have your right dress on we'll chuck you out.''

The researchers have discovered a key mechanism - a type of enzyme - encoded by the Epr3 gene, that enables beneficial bacteria to enter through the plant's outer cell layer.

This might not be an offbeat doctor ''talking to animals'', but an ''active'' dialogue was going on between clover and bacteria, Prof Ronson said.

And these ''molecular conversations'' were also highlighted in a recent Nature-linked article.

The mechanism discovery had opened up ''exciting new research avenues'' and Otago researchers were also undertaking collaborative clover research to boost soil fertility, he said.

john.gibb@odt.co.nz

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