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The greatest problems of plants in tropical climates are drought and high
temperature stress. The latter inhibits plant photosynthesis, disabling
nutrient accumulation and stunting plant growth. Plants have been known to
also accumulate certain chemical compounds under salinity, drought, and
temperature stress, August 2005.

One of these chemicals, glycinebetaine (GB), is the subject of a recent
study, where Xinghong Yang and colleagues from the Chinese Academy of
Sciences Plant Physiology report that the "Genetic Engineering of the
Biosynthesis of Glycinebetaine Enhances Photosynthesis against High
Temperature Stress in Transgenic Tobacco Plants." Their findings appear in
the latest issue of Plant Physiology.

Scientists introduced the betaine aldehyde dehydrogenase (BADH) gene from
spinach into tobacco cells, allowing the transgenic cells to produce GB. The
plants started accumulating GB, and resulted in their increased tolerance to
high temperature stress during growth. Plants, to some extent, were also
able to assimilate carbon dioxide better than their wild-type counterparts
at temperatures as high as 45°C, showing that their photosynthetic pathway
had not been greatly damaged by the heat stress.

The findings suggest a new function of GB in plants, in that it can protect
photosynthesis against high temperatures. They likewise lend strength to the
option of introducing BADH into plant cells in order to effect heat
tolerance, a process which bypasses biosafety concerns, since the gene can
come from a fellow plant.

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