Abstract
The specific genetic changes through which plants adapt to the multitude of environmental stresses are possible because of the molecular regulations in the system. These intricate regulatory mechanisms once unveiled will surely raise interesting questions. Polyamines and hydrogen peroxide have been suggested to be important signaling molecules during biotic and abiotic stresses. Hydrogen peroxide plays a versatile role from orchestrating physiological processes to stress response. It helps to achieve acclimatization and tolerance to stress by coordinating intra-cellular and systemic signaling systems. Polyamines, on the other hand, are low molecular weight polycationic aliphatic amines, which have been implicated in various stress responses. It is quite interesting to note that both hydrogen peroxide and polyamines have a fine line of inter-relation between them since the catabolic pathways of the latter releases hydrogen peroxide. In this review we have tried to illustrate the roles and their multifaceted functions of these two important signaling molecules based on current literature. This review also highlights the fact that over accumulation of hydrogen peroxide and polyamines can be detrimental for plant cells leading to toxicity and pre-mature cell death.
Highlights
Life and stress go hand in hand for all living organisms but in case of plants, being sedentary organisms, stress has to be dealt with in a special way
Influences oxidative and nitrosative status of plants exposed to salinity stress Recovers salinity stress induced damage of plasma membrane (PM) and PM-bound H+- ATPase in salt-tolerant and salt sensitive rice cultivars Transglutaminases catalyse the conjugation of polyamines to photosynthetic complexes and proteins and lead to enhanced photosynthetic activity under abiotic stress conditions Different polyamines showed a variable increase during cold hardening Arabidopsis thaliana plants overexpressing a Cucurbita ficifoia spermidine synthase gene have been demonstrated to become tolerant to multiple stress factors such as low temperature, freezing temperature, drought, salinity, and herbicide Paraquat Spermine inhibited the oxidative degradation of DNA by OH−
Transgenic tobacco plants overexpressing apoplastic polyamine oxidases (PAO) are not able to cope with oxidative burst generated by abiotic factors, causing detrimental effects The same plants mentioned above exhibited increased SOD and CAT expression, which do not exert a protective effect, but rather this increased expression represents an attempt to scavenge surplus H2O2 produced by continuous polyamine oxidation, which suggest that constitutive polyamine oxidation leads to chronic oxidative stress Induction of hypersensitive cell death by H2O2 produced through polyamine degradation
Summary
Life and stress go hand in hand for all living organisms but in case of plants, being sedentary organisms, stress has to be dealt with in a special way. Mittler (2006), studying all prevailing abiotic factor has suggested treating this situation as a new stress condition that he called “stress combination.” Several studies have established the role of ROS as a key signaling molecule in initiating defense mechanism in response to environmental stresses and pathogen infections by modulating pathways involved in different developmental processes and programmed cell death (PCD) (Mittler et al, 2011; Baxter et al, 2014).
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