Flooding Stress: Acclimations and Genetic Diversity

Abstract

Flooding is an environmental stress for many natural and man-made ecosystems worldwide. Genetic diversity in the plant response to flooding includes alterations in architecture, metabolism, and elongation growth associated with a low O(2) escape strategy and an antithetical quiescence scheme that allows endurance of prolonged submergence. Flooding is frequently accompanied with a reduction of cellular O(2) content that is particularly severe when photosynthesis is limited or absent. This necessitates the production of ATP and regeneration of NAD(+) through anaerobic respiration. The examination of gene regulation and function in model systems provides insight into low-O(2)-sensing mechanisms and metabolic adjustments associated with controlled use of carbohydrate and ATP. At the developmental level, plants can escape the low-O(2) stress caused by flooding through multifaceted alterations in cellular and organ structure that promote access to and diffusion of O(2). These processes are driven by phytohormones, including ethylene, gibberellin, and abscisic acid. This exploration of natural variation in strategies that improve O(2) and carbohydrate status during flooding provides valuable resources for the improvement of crop endurance of an environmental adversity that is enhanced by global warming.

Nitrogen metabolism in plants under low oxygen stress

“…Amino acid metabolism is affected by oxygen and energy shortage, however, the role of accumulated amino acids under low oxygen stress is still elusive (Bailey-Serres and Voesenek 2008;Bailey-Serres et al 2012). An interesting comparison of protein and metabolite profiling in response to low oxygen stress between rice and wheat coleoptiles showed in rice coleoptiles, but not in wheat coleoptiles increased abundance of a set of enzymes involved in alanine, serine and glycine biosynthesis with the accumulation of these amino acids in rice coleoptiles (Shingaki-Wells et al 2011).…”

“…NR activity is increased by virtue of its low pH optimum (Stoimenova et al 2007). Phosphorylation of GDH for decreasing its activity under hypoxic condition is hypothesized based on the posttranslational regulation of this enzyme in crayfish Orconectes virilis (Dawson and Storey 2012) goes beyond alanine accumulation (Bailey-Serres and Voesenek 2008;Bailey-Serres et al 2012). It has been suggested that the adaptive response of amino acid metabolism to hypoxic stress consists of a concerted modulation of the flux of organic N going through glutamate and alanine (Limami et al 2008).…”

“…It has been suggested that the adaptive response of amino acid metabolism to hypoxic stress consists of a concerted modulation of the flux of organic N going through glutamate and alanine (Limami et al 2008). Consequently, ATP-consuming pathways such as those involved in glutamine and asparagine biosynthesis are down-regulated in favor of alanine and GABA that generally accumulate, representing the major pool of organic N (Ricoult et al 2005;Rocha et al 2010;Bailey-Serres and Voesenek 2008;Narsai et al 2009). Therefore, it is very likely that modulation of amino acid pathways is the result of posttranslational regulation.…”

“…In this context, plants are threatened by a reduction of the availability of oxygen, during more or less prolonged periods, due to the slower diffusion of oxygen through water and continuing competition for oxygen with respiring microorganisms (Jackson 1985;Drew 1997). Under hypoxic conditions, oxygen concentration in the cells becomes too low to support aerobic respiration, resulting in energy deficit and ultimately cell and tissue death, particularly in plants that are not adapted to flooding and waterlogging (Jackson and Armstrong 1999;Gout et al 2001;Bailey-Serres and Voesenek 2008;BaileySerres et al 2012;Licausi 2013). Major disorders caused by low oxygen stress are related to energy crisis caused by the inhibition of mitochondrial oxidative phosphorylation and subsequent reduction in ATP production.…”

“…However, although only alanine aminotransferase (AlaAT) was found among the core hypoxia-response genes in Arabidopsis (Mustroph et al 2009), nitrogen metabolism was shown to contribute cellular acclimation to low oxygen stress in plants (Bailey-Serres et al 2012;Bailey-Serres and Voesenek 2008). The present review considers the effect of low oxygen stress on several processes related to N metabolism, i.e., nitrate absorption, nitrate and nitrite reduction, Abstract More frequent flooding and waterlogging events due to more heavy precipitation are expected worldwide in the context of climate change.…”