Nitric oxide has emerged as an important signaling molecule in
plants - as in mammals including people. In studies of a tropical medicinal
herb as a model plant, researchers have found that nitric oxide targets a
number of proteins and enzymes in plants.
In collaborative work with the research group of Renu Deswal, a
faculty member, and her doctoral student at the Botany Department,
University of Delhi, India, Agricultural Research Service (ARS) scientist
Autar Mattoo has identified 19 such targeted proteins and enzymes in
Kalanchoe pinnata, also known as "miracle leaf."

These proteins and enzymes are involved in regulating processes from
seed germination to cell development to plant death. Notably, they also
regulate many other important processes including photosynthesis, sugar
metabolism, disease- and stress tolerance in plants.

Mattoo is a plant physiologist with the ARS Sustainable Agricultural
Systems Laboratory at Beltsville, Md.

The collaborative research suggests that the effects of nitric oxide,
a sometimes toxic byproduct of nitrogen oxidation in soil, may have broader
implications in plant processes than realized. Its modification of proteins,
a process called S-nitrosylation, is increasingly recognized as an
ubiquitous regulatory reaction in plants and mammals.

Mattoo and Deswal have shown for the first time that nitric oxide
inactivates Rubisco, a major enzyme involved in carbon dioxide fixation and
photosynthesis in plants.

Kalanchoe represents plants that have a unique method of carbon
dioxide fixation that is shared by succulent plants. Kalanchoe has diverse
possible medicinal benefits suggesting the presence of interesting processes
at work. Mattoo hopes to do similar studies with major crops grown in
different production systems, with an eye toward improving both crop yields
and quality, including nutritional benefits.

Other scientists have studied nitric oxide targets in the most common
model plant, Arabidopsis. Mattoo and collaborators found that Kalanchoe had
some nitric oxide targets in common with Arabidopsis, such as Rubisco and
drought-protective proteins. They also found new protein targets in
Kalanchoe that have not been reported previously


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