Method Found to Slow Plant Growth
12/21/99
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Title: Method found to slow plant growth
Source: BBC Online
Status: Copyright 1999, contact source for permission to reprint
Date: December 21, 1999
Scientists have discovered another gene that will control the
growth of plants.
The gene may allow growers to set the height of their grass, trees
and other plants, eliminating the need to constantly prune and
manicure gardens.
The gene makes a protein that breaks down a steroid hormone in
plant stems.
Researchers from the Salk Institute for Biological Studies in San
Diego, US, used their new-found knowledge to grow "dwarf" versions
of familiar laboratory plants.
A tobacco plant that would normally grow about two metres (six
feet) tall was engineered to mature at about 30 centimetres (12
inches).
"It [the hormone] very much parallels the steroids in football
players. Plants buff up on it,'' Professor Joanne Chory, the Salk
study's senior researcher, told agency reporters. "If you do
something ... so it isn't expressed, you get these little dwarfy
guys.''
Stem elongation
The dwarf versions are identical to the standard plants in every
way but size, she said. The new "dwarf'' gene is called BAS-1. It
regulates the amount of growth hormone - the steroid brassinolide -
within specific plant tissues.
"It appears that brassinolide is made through the plant and then
growth is controlled by selectively inactivating it,'' said
Professor Chory, whose work is reported in the journal Proceedings
of the National Academy of Sciences. "BAS-1 performs this step in
stems, and so switching on BAS-1 will halt stem elongation.''
Professor Chory and her colleagues found the BAS-1 gene by
searching for genes that would reverse the effects of a mutation in
another gene that leads to overly long stems.
BAS-1 is the first gene identified that interacts with both the
steroid hormone and light-detecting pathways, two of the major
systems that control plant growth.
The Salk scientists said although the gene only controls the growth
of plant stems, the discovery is an important addition to our
knowledge of what controls an entire plant's growth.
"Presumably, additional genes will be found that regulate steroid-
induced growth in other parts of the plant, such as leaves and
petals,'' Professor Chory said. "By tinkering with the entire set,
it should eventually be possible to influence every aspect of plant
growth and appearance.''