Molecular Biology, Biotechnology and Genomics of Flooding-Associated Low O2Stress Response in Plants

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Abstract
Low O2 stress to a varied extent affects almost all the organisms either throughout or at specific stages in their life cycle. Plants experience this stress generally in field conditions when flooding, submergence or waterlogging of roots/plants occurs. Low O2 availability during flooding stress results in enormous yield losses in variety of crops. There is overwhelming evidence indicating that adaptations to low O2 stress involves changes in molecular, biochemical, physiological, genetical and anatomical/morphological attributes in plants. Most plants respond to anaerobiosis by switching their respiration from the oxidative (involving complete oxidation of pyruvate into CO2) to the fermentation (involving incomplete oxidation of pyruvate into lactate/ethanol) pathway. Fermentation pathway-related proteins (such as pyruvate decarboxylase and alcohol dehydrogenase enzymes) have been characterized to a significant extent. However, attempts made in altering levels of pyruvate decarboxylase and alcohol dehydrogenase proteins in transgenic plants have not yielded significantly enhanced levels of low O2/flooding stress tolerance as yet. Applying modern tools of transcriptome and proteome analysis, mechanism(s) responsible for low O2/flooding stress tolerance phenotype are being addressed. Progress made in understanding plant responses to low O2 stress is herewith discussed.