Issue (Who cares and why?)
Drought and excessively salty soil are the two most important limiting factors in crop productivity the world over. But for many crops, traditional breeding practices have fallen short of providing real prospects for further improvements in stress tolerance. Hence biotechnologists are studying plants that can cope with extremes, in the hope of finding the secret of their so-called 'osmotolerance' and then incorporating it into more 'osmotically vulnerable' plants.
What has been done?
The Common Ice Plant (Mesembryanthemum crystallinum), is an annual. Due to its capacity to change metabolic strategies from C3-photosynthesis to Crassulacean Acid Metabolism (CAM), this succulent adapts well to low and freezing temperatures (to an astounding 10 degrees below zero Centigrade), withstands seawater concentrations in rooting soil, and is extremely drought-tolerant.
Compared to common plants (e.g., corn, maple trees, spider plants), no genetic model exists for CAM plants. To overcome this deficiency, University of Nevada laboratories have initiated a large-scale genetic screening to isolate the Ice Plant’s mutants defective in CAM or that are salinity or drought stress tolerance. Since Ice Plant is not a mandatory CAM plant, this pathway should not be essential for normal growth and development of the plant. However, CAM may be essential for long-term survival and reproductive success of the plant under the prolonged conditions of salinity or drought stress encountered in its native habitat. Thus far, more than 20,000 plants have been screened and many putative CAM deficient mutants have been isolated.
Impact
Our research identifies and characterizes key structural and regulatory components of this important photosynthetic adaptation. Large-scale sequencing efforts and expression profiling using biotechnological techniques like micro-arrays are providing a rich source of sequence information for identifying novel genes or gene family members and expression patterns peculiar to CAM plants.
If these promising but preliminary results can be replicated and expanded upon, the unique CAM mechanisms of desert succulents could open new routes for engineering crops that are better able to cope with the harsh environments of semi-arid and arid regions that must be pressed into agricultural service in order to feed the world's exploding population.
Contact
John Cushman
Dept. of Biochemistry/200
University of Nevada
Reno, Nevada 89557
jcushman@unr.edu