Plants still harbour a wealth
of potential
Pest Management Group: Plants as Factories for Bioactive
Compounds 29–30 November 2005, Belgrave Square, London
 ‘All
flesh is grass, and the goodliness thereof is as the flower
of the field’, so Isaiah tells us in the Bible. Indeed,
this used to be a standard three-hour final examination essay
topic for botany students – ‘All flesh is grass
– discuss’. It is easy to see why this is true,
although I will not put you through the three-hour essay –
suffice to say that traditionally we use plant products for
food (for ourselves and our livestock), shelter, clothing,
paper and, of course, they produce the oxygen that we breath.
In addition, plants have been a source of medicines and crop
protection agents for centuries. There is an increasing interest
in old Chinese plant-based remedies and it is still true today
that over 50% of all prescribed and over-the-counter medication
taken in the developed world is derived from plant origins.
Some of the earliest insecticides are extracted from plants
and these are still used in organic and conventional farming.
However, despite our reliance on plants many people continue
to suffer from starvation, vitamin deficiencies and food allergies.
Why is this and is there anything that we can do to improve
the situation? The answer is yes. Naturally occurring compounds
in plants have nutritional, health-giving and pharmaceutical
properties and increasingly we are learning how to use those
that we know about; how to increase the level of these ‘bioactives’
through breeding and selection; how to find new, previously
unknown compounds with significant benefits; how to turn the
biological activity found in plants into new chemistries with
uses in a wide variety of different situations; how to develop
new synthetic inhibitors with the same novel modes of action
of these plant products. We already use a wide range of drugs
(aspirin, digitalin) and crop protection agents (nicotine,
rotenone, pyrethrum, azadirachtin) and we are discovering
more. The anti-cancer drug taxol was derived from the Pacific
yew (Taxus brevifolia) and the properties of artemisinin
(from Artemisia spp) are under evaluation as anti-malarials.
The potential benefits of Hoodia gordonii, used as a feeding
deterrent by the Kalahari bushmen, is under evaluation. And
there are many more. Observations of the death of plants growing
under the bottlebrush tree (Callistemon spp) from chlorotic
lesions, has led to the development of new herbicides with
novel modes of action, albeit as a result of coincidence.
But have we derived as much benefit as possible from plants
or is there more that can be done? Today we have the ability
to maximise the production of these products and to introduce
new pathways that allow the plants to ‘manufacture’
complex chemicals cheaply, cleanly and safely. We can add
genes that improve the nutritional qualities of crops (Golden
rice), thereby alleviating deficiency diseases and improving
the quality of life. We can modify plants so that they protect
themselves from insect and disease attack, thereby reducing
the need for crop protection chemicals. We can use herbicide
tolerance to control the devastating parasitic weeds, such
as Striga spp, that cause severe crop losses in developing
countries, as well as making them tolerant to the application
of broad-spectrum, environmentally-friendly herbicides (Roundup
Ready soybeans).
And an important point rarely made about plants is that we
can use them as clean, environmentally friendly ‘factories’
that produce a wealth of novel, biologically active chemicals
with the major waste product being oxygen. As time goes by,
we will discover more and more compounds with more and more
uses. The meeting ‘Plants
as Factories for Bioactive Compounds’ to be held
at Belgrave Square on 29 and 30 November 2005 will discuss
these issues with regard to the way forward, the opportunities,
the successes and the promises for the future.
By Len Copping, SCI Pest Management Group
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