ACHIEVEMENT BY SCIENTIST

Press, Volume CIII, Issue 30540, 8 September 1964, Page 1

ACHIEVEMENT BY SCIENTIST

New Zealander Isolates Cell-Division Hormone

(From Our Own Reporter)

WELLINGTON, September 7.

New light has been thrown on the mechanism of cell division in all living organisms by research in which a New Zealand scientist has taken a major role. The work, described overseas as “a major New Zealand scientific break-through,” may be of great value in research into the causes and cure of cancer.

Last year, Dr. D. S. Letham, of the Fruit Research Division of the D.5.1.R., became the first man to isolate a cell division stimulant —or kinin —in pure crystalline form from any plant.

His find led to collaboration between laboratories in Bradford, Sydney, Wellington and Auckland. The combined efforts of four men have unravelled the chemical structure of the new compound, opening the way to a new understanding of cell division in plants and the possible control of this process for the benefit of agriculture.

The Minister of Science (Mr Talboys> gave details today of what he described as "an outstanding discovery.” Dr. Letham began by seeking a way to stimulate cell division in very young apples, to improve storage' qualities. He set out to discover how cell division in fruit tissue is regulated and was able to show that a plant extract containing a kinin was necessary in apples. He was able to show that kinin activity did occur in the very young, developing fruit and that it disappeared at the same time as cell division ceasedl

Dr. Letham believed further progress depended on characterising the naturallyoccurring kinins. In spite of the failure of overseas workers even to isolate a plant kinin in a pure state, he began isolating and characterising natural fruit kinins. Named “Zeatin” Working first with young plums and then with developing maize seeds, he isolated a crystalline chemical ' which was Riven the name of "zeatin;” Experiments showed it would induce active cell division in carrots. Last July, at the invitation and expense of the French Government, Dr. Letham attended an international symposium in Paris on naturallyoecuring plant growth regulators. Papers presented showed him to be clearly ahead of at least nine other groups of workers overseas also trying to isolate the chemical. Dr. Letham returned to New Zealand determined to continue his major task of identifying the structure. of| zeatin. But Auckland lacked the skills and equipment he needed. He sought help from Dr. J. 8. Shannon, of the Coal Research Section of the Commonwealth Scientific and Industrial Research Organisation, in Sydney, who determined the mass spectrum of zeatin with apparatus not available in New Zealand. Then Dr. I. R. McDonald, of the Chemistry Division of the D.5.1.R., in Wellington, helped with a proton magnetic re-

sonance spectrum for zeatin. The new results, added to Dr. Leatham’s data, narrowed possible formulae to three. Synthesis Dr. G. Shaw, of the Bradford Institute of Technology, agreed to attempt synthesis of the most probable formula by one method while Dr. Letham tried another. Dr. Shaw’s first attempt failed. Dr. Letham was held up for essential materials which could not be flown to New Zealand because of fire hazard. But in a few weeks, Dr.

Shaw found a way around difficulties and produced a small batch of synthetic zeatin, promptly flown to Auckland. Chemical and biological tests showed it to be identical with the substance obtained earlier from maize. The full chemical name for zeatin is 6-(4-hydroxy-3-methylbut-2-enyl) animo purine. Details of the method of proof of this structure and of methods of synthesis have been published in the July issue of the "Proceedings of the Chemical Society.”