A trade article by Cotton Communications

The University of Queensland professor who discovered a protein to protect cotton against Helicoverpa suggests it could produce a huge leap forward for the Australian cotton industry, and potentially other crops, if the protein were used in addition to Bt toxin.

Professor David Craik, from UQ’s Institute for Molecular Bioscience, discovered the protein that can be inserted into a cotton plant’s gene.

"Potentially the caterpillars can destroy 10 to 15 per cent of the crop so the damage it does is enormous," Professor Craik said.

"Such a gene, if inserted into the cotton, could prove a highly effective and natural insecticide, removing the need to use the chemical sprays that are of such environmental concern."

Ally for Bt protein:

The protein, found in plant families which include the Australian violet, is circular in shape. This protects it from attack by biological enzymes because it has no exposed ends.

The result is sufficient strength to repel insect attacks.

About 30% of Australia's cotton crop is genetically modified through Monsanto Co's Ingard and Bollgard products, which are based on a bacterial toxin.

Use of the two applications together could produce a huge leap forward for the Australian cotton industry, and potentially for other crops, Professor Craik told Reuters news agency.

The agricultural applications of this protein have led to the establishment of a company, Cyclagen, which focuses not only on the insecticide potential of this protein in cotton crops, but will also extend the application to other crops in the future.

Using NMR spectroscopy, Professor Craik discovered that the shape of this protein was cyclical, coupled with another unique aspect, cystine knots, making it very stable in biological systems.

Agriculture isn’t the only industry to benefit from the discovery. Because the protein is very stable and resistant to attack from digestive enzymes in the human body, it can be used as a framework for developing drugs that can be taken orally, such as insulin.

African experience:

Professor Craik began his research into the cyclic cystine knot proteins after hearing stories of women in Africa, who were boiling leaves from the Kalata kalata plant to make a tea, which they drank during childbirth to accelerate labour.

He said the fact that the plant was able to withstand boiling and was highly effective when ingested by mouth sparked his interest and led not only to the discovery of the unique shape of the protein but also to the establishment of a company, Kalthera Pty Ltd, devoted to exploring the therapeutic potential of the protein shape.

Professor Craik’s work with the IMB places him at the forefront of scientific discovery as the Institute is now part of the new Queensland Bioscience Precinct at the University of Queensland’s St Lucia campus.

The $105 million QBP will bring together some of the country’s most cutting-edge research projects, and many successful collaborations are expected as a result of access to the suite of bioscience research facilities and expertise not found elsewhere in Australia.

The state-of-the-art facility will house hundreds of scientists from the University’s IMB, CSIRO and the Queensland Department of Primary Industries. The QBP was jointly funded by CSIRO and UQ, the federal and state governments as well as funds from a private donor.

Kalata B1 is not only a cyclic protein but it also sports a biological knot … with a twist. Small cyclic proteins of microbial origin are quite common.

However macrocyclic proteins, such as kalata B1, are not so frequent and seem to be favoured
by higher plants. Kalata B1 is 29 amino-acids long and starts, like most of its protein buddies, as a linear sequence. As it evolves through the plant’s secretory pathway it manages to create three disulfide bridges, two of which form a ring. The third plunges through the ring creating a knot. Though mathematicians may not qualify this as a true knot, once the protein sequence is cyclized it cannot be undone without damaging the chain. And for the layman a good definition of a knot is something one cannot undo.

In addition to its three cystine bridges and cyclization, kalata B1 has another trick. It has a twist. The biological significance of this twist is unknown but from a structural point of view it is fascinating. As David Craik from the Centre for Drug Design and Development in Queensland, Australia, explains, imagine a thin strip of paper. There are two ways of attaching the ends. You can attach them as you would a bracelet, i.e. without a twist. Or you can add one twist and then attach the ends.

Plant cyclotides are now grouped into two types: bracelet cyclotides and Moebius cyclotides. Kalata B1 is a Moebius cyclotide.

Despite the knowledge of such an intricate knotting system, scientists still do not know
what the precise role of kalata is in the plant. There is proof of insecticidal and antimicrobial properties.

It has a major effect on Helicoverpa punctigera larvae by stunting their growth and development. However, it was shown that kalata B1 does not inhibit protein and starch degradation hinting that it does not function as a proteinase or alphaamylase inhibitor.