Physiological and transcriptomic characterization of submergence and reoxygenation responses in soybean seedlings

Abstract

Complete inundation at the early seedling stage is a common environmental constraint for soybean production throughout the world. As floodwaters subside, submerged seedlings are subsequently exposed to reoxygenation stress in the natural progression of a flood event. Here, we characterized the fundamental acclimation responses to submergence and reoxygenation in soybean at the seedling establishment stage. Approximately 90% of seedlings succumbed during 3 d of inundation under constant darkness, whereas 10 d of submergence were lethal to over 90% of seedlings under 12 h light/12 h dark cycles, indicating the significance of underwater photosynthesis in seedling survival. Submergence rapidly decreased the abundance of carbohydrate reserves and ATP in aerial tissue of seedlings although chlorophyll breakdown was not observed. The carbohydrate and ATP contents were recovered upon de-submergence, but sudden exposure to oxygen also induced lipid peroxidation, confirming that reoxygenation induced oxidative stress. Whole transcriptome analysis recognized genome-scale reconfiguration of gene expression that regulates various signalling and metabolic pathways under submergence and reoxygenation. Comparative analysis of differentially regulated genes in shoots and roots of soybean and other plants defines conserved, organspecific and species-specific adjustments which enhance adaptability to submergence and reoxygenation through different metabolic pathways.

Waterlogging and submergence stress: affects and acclimation

“…In these pathways, ethylene production is perceived by ETR1 (ethylene-binding receptors), which activates EIN2/EIN3 (ethylene insensitive) and leads to expression of ethylene response factor (ERFs) transcription factors in the nucleus (Pierik et al, 2006). Recent transcriptome and/or microarray data of Arabidopsis (Hsu et al, 2011;Licausi et al, 2011), maize (Thirunavukkarasu et al, 2013), cotton (Christianson et al, 2010), soybean (Tamang et al, 2014), Jatropha (Juntawong et al, 2014), Taxodium (Qi et al, 2014) has provided a diverse set of transcripts operating during the stress. It provides a deeper understanding of the molecular mechanisms occurring when plants are confronted with waterlogging stress followed by hypoxia.…”

Ethylene-Mediated Acclimations to Flooding Stress

“…Root cell membrane damage resulting from this lipid peroxidation is likely the cause of another frequently observed symptom of reaeration: dehydration stress. Despite excessive water in the soil, some plants display symptoms of water deficit after reoxygenation, such as wilted leaves, and up-regulate dehydration-responsive genes (Setter et al, 2010;Fukao et al, 2011;Tamang et al, 2014;Tsai et al, 2014). These symptoms could be caused by reduced hydraulic conductance of flooded roots (Rodríguez-Gamir et al, 2011).…”

Arabidopsis CML38, a Calcium Sensor That Localizes to Ribonucleoprotein Complexes under Hypoxia Stress

“…In response to these conditions, plants employ a variety of short-term and long-term adaptation strategies, including (1) increases in glycolytic flux to provide ATP; (2) elevation of fermentation metabolism to regenerate NAD + for glycolysis; (3) induction of morphological and developmental changes (e.g. aerenchyma, adventitious root formation, and root and stem elongation) to elevate oxygen levels in waterlogged roots; and (4) increased capacity to avoid/repair the oxidative damage that occurs during posthypoxia reoxygenation (Blokhina et al, 2003;Ella et al, 2003;Tamang et al, 2014).…”