CYRIL, JENITH*, GARY POWELL, AND WM. VANCE BAIRD. Departments of Horticulture and Biological Sciences, Clemson University, Clemson, SC 29634. - Cloning and characterization of fatty acid desaturase genes from bermudagrass (Cynodon spp).
All plants are exposed to environmental stress at some time during
their life cycle. Plants respond to such stress by regulating the
expression of genes ultimately responsible for synthesis of compounds
that help in adapting to the stress. Cold temperature is an important
stress affecting crops in the U.S. Some plants are more tolerant to
low temperature stress than others, and many of these
"acclimate" to withstand previously lethal low temperatures.
Acclimation is a naturally occurring physiological process in many
temperate perennial plants. In addition to synthesis of compounds
like osmolytes and cryoprotectants, the degree of unsaturation of
membrane lipid fatty acids contributes to the ability of these plants
to withstand prolonged exposure to low temperature. Bermudagrass is
a warm season turfgrass, which shows an increase in the synthesis of
the tri-unsaturated fatty acid, linolenic acid during
cold-acclimation. In addition, there is concomitant decrease in the
amount of the di-unsaturated fatty acid linoleic acid. There are
cultivar-specific differences in the timing and magnitude of these
changes, but the basic pattern is the same. We are currently cloning
the omega-3 and omega-6 desaturase genes, of the fatty acid
biosynthetic pathway leading to linolenic acid. We used a PCR-based
cloning method, with degenerate primers, to clone members of the
omega-3 and omega-6 desaturase gene families. Gene family sizes will
be determined by genomic Southern blot analysis. Full-length cDNA
clones will be obtained by rapid amplification of cDNA ends (RACE). A
genomic library, in lambda EMBL3, will be screened to obtain the
full-length gene clones. Expression patterns of the desaturase genes
in different tissues/organs, during cold acclimation, also will be
investigated.
Key words: bermugadrass, cold acclimation, DNA sequence, fatty acid desaturase, gene expression