Isolation
and Characterization of Cold Responsive Genes.
The citrus producing areas of the Unite States are
subjected to occasional freezes that can be devastating.
In Texas, the freezes of 1951 and 1962 killed together
125,000 acres of citrus trees. Subsequent freezes
of 1983 and 1989 almost wiped out the Texas Citrus
Industry, which is currently reduced to about 26,000
acres. Our lab is very interested in studying the
expression of genes induced by cold in the cold
hardy Poncirus trifoliata (PT) and in the cold sensitive
Mexican lime (ML).
We recently isolated a very interesting cold responsive
gene from PT, which we called CLT. At 28°C only
one transcript is produced (Fig.1, 0h), as the
plant is acclimated to -1 °C for longer times,
other transcripts are produced. After 7 days of
acclimation 5 transcripts can be seen.
The open reading frame (ORF) of four transcripts
(including the constitutive) are the same, but
the 3' untranslated regions (3' UTR) are different
because of intron retention. One of the five transcript
retains an intron in a region that interrupts
the ORF and create a new ORF without creating
premature stop codon. When we compared the expression
of the same gene in the cold sensitive ML and
in Rio Red grapefruit the expression pattern is
completely different. After 7-day of acclimation,
ML express poorly the inducible transcripts (Fig
2), and Rio Red moderately (Fig. 3), following
their cold tolerance pattern; PT very cold hardy,
Rio Red is moderate, and ML very cold sensitive.
Other Ongoing Research Projects
- Development of a broad spectrum disease
resistance system for citrus
We are developing a system to make the first
signal of the hypersensitive response pathway
constitutive and at the same time inhibit the
cell dead pattern that takes place during the
hypersensitive response. We already isolated
and characterized the genes necessary for the
project and are now preparing for the genetic
transformation step.
- Fingerprinting the two species of
root-feeding aphids in cruciferous using AFLP.
- Fingerprinting false spider mites
in citrus using AFLP.
- Development of new improved citrus
cultivars.
This is a long term research project
to develop improved cultivars of orange, grapefruit,
lemons and pummelos . We are field testing several
potential improved cultivars developed in our
lab, including a excellent seedless lemon. Photos
are shown elsewhere in the home page. Since
this is a proprietary project, no information
on the method used are provided.
- We are testing several rootstocks
in a attempt to find a replacement for sour
orange rootstock, which is basically the only
rootstock used in Texas.
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