Differential Molecular Responses of Rice and Wheat Coleoptiles to Anoxia Reveal Novel Metabolic Adaptations in Amino Acid Metabolism for Tissue Tolerance    

Abstract

Rice (Oryza sativa) and wheat (Triticum aestivum) are the most important starch crops in world agriculture. While both germinate with an anatomically similar coleoptile, this tissue defines the early anoxia tolerance of rice and the anoxia intolerance of wheat seedlings. We combined protein and metabolite profiling analysis to compare the differences in response to anoxia between the rice and wheat coleoptiles. Rice coleoptiles responded to anoxia dramatically, not only at the level of protein synthesis but also at the level of altered metabolite pools, while the wheat response to anoxia was slight in comparison. We found significant increases in the abundance of proteins in rice coleoptiles related to protein translation and antioxidant defense and an accumulation of a set of enzymes involved in serine, glycine, and alanine biosynthesis from glyceraldehyde-3-phosphate or pyruvate, which correlates with an observed accumulation of these amino acids in anoxic rice. We show a positive effect on wheat root anoxia tolerance by exogenous addition of these amino acids, indicating that their synthesis could be linked to rice anoxia tolerance. The potential role of amino acid biosynthesis contributing to anoxia tolerance in cells is discussed.

A Shoot-Specific Hypoxic Response of Arabidopsis Sheds Light on the Role of the Phosphate-Responsive Transcription Factor PHOSPHATE STARVATION RESPONSE1

“…Possibly, the ratio of 3-PGA/Pi could serve as a signal, as it increased under the two stress conditions. Levels of 3-PGA were significantly increased under hypoxia, while they tended to decrease under phosphate deficiency, a trend observed previously (low Pi, Fredeen et al, 1990;Jacob and Lawlor, 1992;Rao and Terry, 1995;and hypoxia, Biemelt et al, 1999;Shingaki-Wells et al, 2011;Ampofo-Asiama et al, 2014).…”

Nitrogen metabolism in plants under low oxygen stress

“…To test whether the accumulation of these amino acids is related to the tolerance of oxygen deprivation in rice, the authors supplemented the medium used for rice and wheat growth with a combination of these amino acids. The results showed a positive effect of exogenous addition of a mix of three (Ser/Ala/Gly) or two (Ser/Ala) amino acids on wheat root tolerance of oxygen deprivation thus indicating that their synthesis could be linked to rice anoxia/hypoxia tolerance (Shingaki-Wells et al 2011). Metabolic and transcriptomic responses to oxygen availability in rice embryos and young seedlings are in agreement with these findings showing that the changes in enzymes and amino acid contents are sustained by changes in expressions of corresponding genes (Narsai et al 2009).…”

“…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). To test whether the accumulation of these amino acids is related to the tolerance of oxygen deprivation in rice, the authors supplemented the medium used for rice and wheat growth with a combination of these amino acids.…”

“…Sugar degradation, glycolysis and fermentation were increased in consequence to enable germination and growth under low oxygen condition (Hattori et al 2009). In coleoptiles of rice growing under low oxygen the abundance of SUS4, enzymes involved in several steps of glycolysis, e.g., pyrophosphate (PPi)-Fru-6-P 1-phosphotransferase, Fructose-bisP aldolase, triosephosphate isomerase, glyceraldehyde-3-phosphate dehydrogenase and enzymes of ethanolic fermentation, ADH1 and PDC1 increased significantly compared to aerobic condition (Shingaki-Wells et al 2011). Up-regulation of hypoxia-induced genes of sugar metabolism was mediated by the protein kinase CIPK15 (Calcineurin B-like protein kinase interfering protein kinase) that activated the stress sensor SnRK1A (sugar non-fermenting related protein kinase) thus connecting sensing of O 2 -deficiency signal to the flooding response of rice seedling (Lee et al 2009).…”

Effects of externally supplied BSA on ZR, IAA, ABA, GA of plant Cinnamomum camphora cutting seedlings and root

“…The different plant species response to exogenous organic nitrogen is variable. For example, a positive effect of exogenous addition of a mix of three (Serine/Alanine/Glycine) or two (Serine/Alanine) amino acids on wheat root tolerance of oxygen deprivation was detected [19] . Reduced glutathione treatment promoted tomato seedling cuttings root formation [15] .…”