Agriculture Reference
In-Depth Information
Chapter 17
Dealing with Environmental Stresses: Role
of Polyamines in Stress Responses
Rinukshi Wimalasekara and Günther F. E. Scherer
Abstract
Extreme environmental conditions including drought, high- and low-
temperatures, high salinity, mineral deficiency and heavy metal toxicity severely
affect crop loss worldwide. Improvement of plants for enhanced resistance to
adverse climatic conditions is a key issue in sustainable crop production, strength-
ening the global food safety. Understanding stress tolerance mechanisms of plants
are a prime importance in crop improvement. Among the array of components
involved, plant polyamines (PAs) are identified as one such group of components
that play an important role in diverse environmental stress responses. PAs are small
organic cations containing two or more amino groups. These are growth regula-
tors present widely in all living organisms with varying quantities ranging from
micromolar to milimolar. In plants, the most abundantly found PAs are di-amine
putrescine, tri-amine spermidine and tetra-amine spermine. Accumulation of long
chain and conjugated forms of PA occur under some environmental and growth con-
ditions. Biosynthesis, transport, degradation and conjugation determine the level
of PAs and vary throughout a plant life cycle. Catabolism of PAs by amine oxi-
dases is trivial in the regulation of cellular levels of PAs. Apart from the essential
functions in growth and development, PAs play a key role in environmental stress
responses such as drought, chilling, salinity, mineral deficiencies such as potassium,
nitrogen and magnesium deficiency, heavy metal toxicity, mechanical injuries and
defence signalling against pathogens. Differential transcriptional regulation of sev-
eral stress-related genes in PA-overexpressed transgenic plants suggests potential
signalling function of PAs in stress responses. Genetic manipulation of crop plants
for altered regulation of PA biosynthesis/catabolism may lead to improved stress
tolerance potential. This article summarizes the recent findings on the involvement
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