Sources:
Adh
-l+ - most L. esculentum; sporadic in L. pimpinellifolium
-11 - LA 1221 L. esculentum cv. VFNT Cherry; many L. esculentum var. cerasiforme and L. pimpinellifolium
-12 - LA 1416 L. pimpinellifolium; LA 247 L. parviflorum
-14 - LA 716
S. pennellii
-19 - LA 381 L. pimpinellifolium
Pgm
-1+ - all material tested (survey has been limited)
Pgm
-2+ - most L. esculentum and L. pimpinellifolium
-21 - LA 1246 L. pimpinellifolium; LA 716 S. pennellii
-23 - LA 1690 L. pimpinellifolium; LA 1724 S. pennellii
Tanksley, S. D. An efficient and economical design for starch gel electrophoresis.*
In recent years, starch gel electrophoresis of enzymes has become a popular tool for genetic and
evolutionary studies in both plants and animals. As the number of investigators using the technique has grown, so
has the number of designs of equipment. Although many factors can affect the quality of the results produced by
electrophoresis, the design of equipment is the one variable over which a researcher has most control. Good results
can be produced on water-cooled units, but these are expensive, difficult to build, cumbersome to use, and prone to
break down. Air cooled (simple refrigeration) systems are less expensive and easier to build, but the results are
generally inferior.
Described here is the electrophoresis system used in our isozyme analysis of tomato species. It is as easy
and inexpensive to construct as an air cooled system, yet produces results as good as or better than water cooled
systems. A single unit which will hold one 15 cm by 20 cm gel consists of 2 buffer tanks with built-in electrodes, a
base, and a gel mold (Fig. 1). The gel mold, which holds the gel during electrophoresis, is made of single strength
silica glass and rests on a sponge pad which is part of the base. The ends of this pad feed into reservoirs of water at
either end of the base. Heat built up in the gel during electrophoresis passes through the glass mold and is
efficiently dissipated from the exposed bottom side of the pad by convection and evaporation. At either end of the
base rest the buffer tanks with electrodes. These tanks, which receive current from the base, can be easily lifted off
for cleaning.
This system permits electrophoresis to be carried out in almost any refrigeration unit so long as a small fan
or some other device is installed to promote air circulation. The sponge pad provides uniform cooling and buffers the
gel from temperature changes when the refrigerator is open. Four units will easily fit into a standard household
refrigerator. Although the system is compatible with most high voltage power supplies, it is most economical to
purchase kits and assemble them yourself (e.g. Heathkit H. V. power supply Model IP-17).
Maintenance is minimal. The water reservoirs which feed the sponge pad must be filled about once a week
with distilled water, and after each electrophoresis run it is a good idea to remove the buffer tanks and rinse with
distilled water. A complete unit can be constructed from material readily available in most cities. The cost of one
unit, minus power supply, is $30-$35, and with a minimum of tools a novice can build one in 4-5 hours.
In addition to this basic electrophoresis system, trays have been designed which allow two gels to be
stained for enzyme activity in a volume of solution which would normally stain only one gel (50 ml). With
biochemicals so expensive this can result in a substantial saving over a short period of time.
Instructions for building the above described equipment can be obtained from the author (Vegetable Crops
Department, University of California, Davis, CA 95616).
*Design registered with the University of California Board of Patents, Berkeley, CA 94720.
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