Plant mitochondria under hypoxia: a cross-talk between nitric oxide, hemoglobin and oxygen

Abstract

The major goal of the present study is to describe the mechanisms by which plants adapt to deficiencies in the electron transport chain, either in terms of lack of the functional electron transport complex or lack of final electron acceptor (oxygen). In plants, the main function of class 1 hemoglobins is to scavenge nitric oxide (NO). Under hypoxia and anoxia, there is a significant increase in hemoglobin expression which upregulates the turnover of the Hb-NO cycle. This cycle not only participates in the electron transport chain, but NO influences various signalling processes which govern plant development, morphology and physiology. The current study demonstrates that NO produced under hypoxia induces AOX1A gene expression, which is translated to a higher AOX activity and leads to a shift towards biosynthesis of amino acids. It also demonstrates that respiratory complex I deficiency results in low NO levels and upregulation of fermentation pathways. The current study undertakes extensive efforts to characterise the morphological, biochemical and physiological effects of modified hemoglobin expression in barley. Results show a difference in observations when compared with other model organisms such as Arabidopsis. NO also influences the process of senescence. Hence we investigate the process of senescence under hypoxia and in plants with modified hemoglobin expression. The study also involves generating of three barley transgenic lines to further study the role of hemoglobin in plant development, physiology, pathology, nutrition and stress tolerance.