An Arabidopsis Gene Extends the Life of Tomato and Petunia

C. S. Prakash prakash at acd.tusk.edu
Wed Jun 4 10:56:50 EST 1997


A commentary on Nature Biotechnology paper concerning Ethylene receptors
from June 1997 ISB NewsReport (http://www.nbiap.vt.edu)

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        FOREVER FLOWERS AND FRUITS
        - An Arabidopsis Gene Extends the Life of Tomato and Petunia


        When your tomato or banana fruits turn mushy or if those
carnation flowers in the vase droop quickly, blame it on
ethylene. This gaseous hormone elicits a cascade of developmental
responses in plants resulting in fruit ripening and flower
senescence. Biotechnologists have sought to extend the shelf life
of fruits and flowers by silencing the genes involved in ethylene
biosynthesis. However, such transgenic fruits and flowers still
respond to ethylene produced by other plants and begin to decay
just like non-transgenic plants.

        A recent report describes a new solution to this problem that
entails the use of a hormone receptor gene from Arabidopsis which
confers ethylene insensitivity (1). Tomato fruits ripened very
slowly on plants engineered with this gene, while petunia flowers
from transgenic plants remained fresh longer than their
nontransgenic counterparts. The dominant mutant etr1-1 gene,
cloned from Arabidopsis by Elliot Meyerowitz and colleagues at
CalTech, encodes a protein that alters the perception of ethylene
by plant cells and thus makes the plant unresponsive to the
hormone (2).

        A team led by Harry Klee, who initiated the  work while at
Ceregen Technology  (Monsanto Company) and continued it at the
University of Florida, introduced this gene into tomato and
petunia using Agrobacterium vectors. Transgenic tomato plants
exposed to ethylene exhibited a dramatically delayed fruit
ripening and senescence compared with those on untransformed
plants. Harvested tomato fruits retained their original golden
yellow color even when stored for 100 days while the regular
tomato fruits soon "turned red, became soft and started to rot".
Similarly, petunia flowers with the 'ethylene- insensitive' gene
senesced slowly and remained longer on the plant. When exposed to
ethylene, the transgenic flowers stayed fresh for nine days in
the vase while the untransformed flowers wilted within just three
days.

        According to the researchers, the ethylene insensitive gene from
Arabidopsis  may have to be weakened by molecular alterations to
ensure its broad application, because fruits and vegetables
eventually must respond to ethylene for ripening to proceed. The
use of appropriate promoters may also permit targeted ripening.
Monsanto scientists anticipate that the immediate beneficiary of
their finding will be the floriculture business, a multibillion
dollar industry worldwide.

        Many chemicals that affect ethylene synthesis or its action,
which are currently  in use to extend the shelf life of flowers,
are being banned because of environmental concerns (3). The
floriculture industry thus may gain substantially from the use of
the 'ethylene-insensitive' gene by making their colorful blooms
last longer either on plants or in vases. Arabidopsis may never
be considered pretty enough to be taken seriously by nurserymen
but the Nature Biotechnology study clearly underscores one of the
potential pay-offs to agriculture from the investment in research
on this humble weed.

1.  J. Q. Wilkinson et al. 1997. Nature Biotechnology 15: 444-447.
2.  C. Chang et al. 1993. Science 262: 539-544.
3.  M. Bouzayen & J. Pech. 1997. Nature Biotechnology 15: 418

C. S. Prakash
Center for Plant Biotechnology Research
Tuskegee University
mailto:prakash at acd.tusk.edu







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