Polyamines (PAs) are positively charged amines that are present in all organisms. In addition to their functions specific to growth and development, they are involved in responding to various biotic and abiotic stress tolerance functions. The appropriate concentration of PA in the cell is maintained by a delicate balance between the catabolism and anabolism of PAs, which is primarily driven by two enzymes, namely diamine oxidase and polyamine oxidase (PAO). PAOs have been found to be localized in multiple subcellular locations, including peroxisomes. This paper presents a holistic account of peroxisomal PAOs. PAOs are flavin adenine dinucleotide-dependent enzymes with varying degrees of substrate specificity. They are expressed differentially upon various abiotic stress conditions, namely heat, cold, salinity, and dehydration. It has also been observed that in a particular species, the various PAO isoforms are expressed differentially with a spatial and temporal distinction. PAOs are targeted to peroxisome via a peroxisomal targeting signal (PTS) type 1. We conducted an extensive bioinformatics analysis of PTS1s present in various peroxisomal PAOs and present a consensus peroxisome targeting signal present in PAOs. Furthermore, we also propose an evolutionary perspective of peroxisomal PAOs. PAOs localized in plant peroxisomes are of potential importance in abiotic stress tolerance since peroxisomes are one of the nodal centers of reactive oxygen species (ROS) homeostasis and an increase in ROS is a major indicator of the plant being in stress conditions; hence, in the future, PAO enzymes could be used as a key candidate for generating abiotic stress tolerant crops.
Abiotic stress is a major constraint on crop productivity and in the agricultural field, multiple abiotic stresses act synchronously leading to substantial damage to plants. A common after-effect of abiotic stress-induced damage in plants is an increased concentration of reactive oxygen species (ROS) leading to oxidative damage. Glutathione reductase (GR) plays a significant role in curtailing ROS. Apart from the GR enzyme, the peroxisome as an organelle also plays a significant role in ROS homeostasis. Here, we report a peroxisome localized GR, whose expression was found to be upregulated by various abiotic stresses. The in silico analysis also revealed that the peroxisomal localization of GR could be a common phenomenon in angiosperms, suggesting that it could be a suitable candidate against abiotic stress combinations.
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