Waterlogging-induced changes in fermentative metabolism in roots and nodules of soybean genotypes

Abstract

Waterlogging blocks the oxygen supply to the root system which inhibits respiration, and greatly reduces the energy status of cells that affect important metabolic processes. This study evaluated fermentative metabolism and carbohydrate contents in the root system of two soybean (Glycine max L. Merril) genotypes under hypoxic and post-hypoxic conditions. Nodulated plants (genotypes Fundacep 53 RR and BRS Macota) were grown in vermiculite and transferred to a hydroponic system at the reproductive stage. The root system was submitted to hypoxia by flowing N 2 (nitrogen) gas in a solution for 24 and 72 h. For recovery, plants returned to normoxia condition by transfer to vermiculite for 24 and 72 h. Fermentative enzyme activity, levels of anaerobic metabolites and carbohydrate content were all quantified in roots and nodules. The activity of alcohol dehydrogenase, pyruvate decarboxylase and lactate dehydrogenase enzymes, as well as the content of ethanol and lactate, increased with hypoxia in roots and nodules, and subsequently returned to pre-hypoxic levels in the recovery phase in both genotypes. Pyruvate content increased in nodules and decreased in roots. Sugar and sucrose levels increased in roots and decreased in nodules under hypoxia in both genotypes. Fundacep RR 53 was more responsive to the metabolic effects caused by hypoxia and post-hypoxia than BRS Macota, and it is likely that these characteristics contribute positively to improving adaptation to oxygen deficiency.Keywords: Glycine max, oxygen deficiency, enzyme activities, anaerobic metabolites, sugars IntroductionSoil waterlogging is a common abiotic stress worldwide in cultivated areas and influences the composition and productivity of soybean (Glycine max L. Merril) and most crops species (Jackson and Colmer, 2005;Githiri et al., 2006;Sairam et al., 2009;Kokubun, 2013). In waterlogged soils, gas exchanges between root systems and soil porous spaces are limited due to oxygen diffusion resistance that is around 10,000 times higher in water than in the air (Armstrong et al., 1994;Dongen et al., 2003;Zabalza et al., 2009;Bailey-Serres et al., 2012).Decrease in the oxygen level is the main factor that causes stress, leading to a chain signaling that unleashes a series of metabolic changes (Horchani et al., 2009), such as N metabolism and interconversion of amino acids (Puiatti and Sodek, 1999;Oliveira et al., 2013), changes in carbohydrates levels and energetic metabolism (Sousa and Sodek, 2002a), in an effort to secure plant survival and growth when exposed to hypoxic stress (Geigenberger, 2003). Anaerobic metabolism is activated under low oxygen concentration and as a consequence, there is a significant decrease in energy production that is derived mainly from glycolysis in contrast to oxidative phosphorylation (Kumutha et al., 2008;Horchani et al., 2009;Sairam et al., 2009;Zabalza et al., 2009). Plant survival under these conditions depends almost exclusively on anaerobic metabolism (Sousa and Sodek, 2002a).Due to the lack of O 2 as the fi...

Nitrogen source influences the antioxidative system of soybean plants under hypoxia and re-oxygenation

“…Altouhg genotypes Fundacep 53 RR and BRS Macota respond distinctly to hypoxia, tolerant and sensitive, respectively (Borella et al, 2014(Borella et al, , 2017, the antioxidative metabolism here studied was not correlated with tolerance mechanisms that differentiate genotypes and it is probably due to the short duration of flooding of the root system (Wang et al, 2009). However, tolerant species increase the activity of antioxidant enzymes to counteract the oxidative effects (Sairam et al, 2009;Simova-Stoilova et al, 2012).…”

“…The study was carried out at Federal University of Pelotas -Campus Capão do Leão (31º 52' 32" S and 52º 21' 24" W; altitude: 16 m), with two soybean [Glycine max (L.) Merril] genotypes, Fundacep 53 RR and BRS Macota, identified previously to respond distinctly to hypoxia (Borella et al, 2014(Borella et al, , 2017. The experiment comprised two groups, nodulated (N 2 -fixing) and nonnodulated (nitrate supplied) plants, grown in a greenhouse under natural light and temperature conditions.…”

Hypoxia-Responsive Root Hydraulic Conductivity Influences Soybean Cultivar-Specific Waterlogging Tolerance

“…Moreover, the importance of root hydraulic conductivity for water channel-induced permeability needs to be investigated among cultivars with specific hypoxic responses (e.g., examining the effects of aquaporin inhibitors such as silver nitrate or mercury compounds) [47]. Furthermore, hypoxia-inducible root-related transcription factors [48], fibrillins [49], nuclear-related proteins [50], and the special fermentative metabolic system in soybean roots [51] [52] may affect cultivar-specific waterlogging tolerance and will also need to be studied to further characterize the mechanism underlying waterlogging tolerance.…”

Respostas morfológicas ao alagamento em espécies arbóreas de florestas ribeirinhas subtropicais brasileiras

“…A espécie P. rigida sob alagamento total apresentou menor comprimento da raiz, indicando sensibilidade nessa condição hídrica. A redução do crescimento das raízes é uma resposta comumente observada em condições de inundação e ocorre em consequência tanto da limitação na disponibilidade de oxigênio como pela presença de fitotoxinas resultantes do metabolismo fermentativo (Mielke et al 2003, Borella et al 2014. Além disso, a redução da massa seca da parte aérea, das raízes e total e no diâmetro do caule observada nas plantas de P. rigida submetidas aos tratamentos de IP e IT, também é considerada uma resposta clássica em situações de saturação hídrica, conforme observado em estudos com diferentes espécies (Gomes & Kozlowski 1980, Kozlowski & Pallardy 1984, Medri et al 2007.…”