Abstract
Osmotin is an abundant cationic multifunctional protein discovered in cells of tobacco (Nicotiana tabacum L. var Wisconsin 38) adapted to an environment of low osmotic potential. Beside its role as osmoregulator, it provides plants protection from pathogens, hence also placed in the PRP family of proteins. The osmotin induced proline accumulation has been reported to confer tolerance against both biotic and abiotic stresses in plants including transgenic tomato and strawberry overexpressing osmotin gene. The exact mechanism of induction of proline by osmotin is however, not known till date. These observations have led us to hypothesize that osmotin could be regulating these plant responses through its involvement either as transcription factor, cell signal pathway modulator or both in plants. We have therefore, undertaken the present investigation to analyze the osmotin protein as transcription factor using bioinformatics tools. The results of available online DNA binding motif search programs revealed that osmotin does not contain DNAbinding motifs. The alignment results of osmotin protein with the protein sequence from DATF showed the homology in the range of 0-20%, suggesting that it might not contain a DNA binding motif. Further to find unique DNA-binding domain, the superimposition of osmotin 3D structure on modeled Arabidopsis transcription factors using Chimera also suggested absence of the same. However, evidence implicating osmotin in cell signaling were found during the study. With these results, we therefore, concluded that osmotin is not a transcription factor, but regulating plant responses to biotic and abiotic stresses through cell signaling.
Highlights
The growth and productivity of crop plants depend largely on their vulnerability to environmental stresses
Overall results suggest that osmotin protein lacks leucine zippers and HTH motifs, the two predominant and important DNA binding motifs
The alignment results of osmotin with the protein sequence from Database of Arabidopsis transcription factors (DATF) showed the homology in the range of 0-20%, suggesting that it does not contain a DNA binding motif
Summary
The growth and productivity of crop plants depend largely on their vulnerability to environmental stresses. Water deficit, and temperature stress are the major constraints that limit agricultural production [1]. Plants respond to these conditions with an array of biochemical and physiological adaptations, which involve the function of many stress-related genes. Any attempt to improve the stress tolerance requires a better understanding of the underlying physiological, biochemical and molecular events [2]. Compatible solutes have the capacity to persevere the activity of enzymes that are in saline solutions. These compounds have minimal effect on pH or charge balance of the cytosol or luminal compartments of organelles. Compatible solutes include low molecular weight sugars, organic acids, polyols and nitrogen containing compounds such as amino acids, amides, imino acids, proteins and quaternary ammonium compounds [4]
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