Biochemical and Anatomical Investigation of Sesbania herbacea (Mill.) McVaugh Nodules Grown under Flooded and Non-Flooded Conditions

Abstract

Sesbania herbacea, a native North American fast-growing legume, thrives in wet and waterlogged conditions. This legume enters into symbiotic association with rhizobia, resulting in the formation of nitrogen-fixing nodules on the roots. A flooding-induced anaerobic environment imposes a challenge for the survival of rhizobia and negatively impacts nodulation. Very little information is available on how S. herbacea is able to thrive and efficiently fix N2 in flooded conditions. In this study, we found that Sesbania plants grown under flooded conditions were significantly taller, produced more biomass, and formed more nodules when compared to plants grown on dry land. Transmission electron microscopy of Sesbania nodules revealed bacteroids from flooded nodules contained prominent polyhydroxybutyrate crystals, which were absent in non-flooded nodules. Gas and ion chromatography mass spectrometry analysis of nodule metabolites revealed a marked decrease in asparagine and an increase in the levels of gamma aminobutyric acid in flooded nodules. 2-D gel electrophoresis of nodule bacteroid proteins revealed flooding-induced changes in their protein profiles. Several of the bacteroid proteins that were prominent in flooded nodules were identified by mass spectrometry to be members of the ABC transporter family. The activities of several key enzymes involved in nitrogen metabolism was altered in Sesbania flooded nodules. Aspartate aminotransferase (AspAT), an enzyme with a vital role in the assimilation of reduced nitrogen, was dramatically elevated in flooded nodules. The results of our study highlight the potential of S. herbacea as a green manure and sheds light on the morphological, structural, and biochemical adaptations that enable S. herbacea to thrive and efficiently fix N2 in flooded conditions.

Long-Term Waterlogging as Factor Contributing to Hypoxia Stress Tolerance Enhancement in Cucumber: Comparative Transcriptome Analysis of Waterlogging Sensitive and Tolerant Accessions

“…Aspartate aminotransferase (AspAt) transfers N from aspartate to glutamate, which is a substrate of GABA synthesis, where GAD (glutamate decarboxylase) is involved [ 70 ]. Aspartate aminotransferase and glutamate decarboxylase also participate in amino acid metabolism and serves as regulators of cytoplasmic pH as it becomes lower during hypoxic stress, mostly due to enhanced lactic acid production [ 71 ].…”

Ion-Exchange Chromatography Coupled to Mass Spectrometry in Life Science, Environmental, and Medical Research

“…While they did not report formal LLODs and LLOQs, they recorded values as low as 0.7 nmol/mL. Other examples of IC-MS in microbial applications include metabolomic analysis of the root endophytic fungus Piriformospora indica and analysis of metabolites rhizobia formed with the symbiont Sesbania herbacea, a native North American fast-growing legume. IC-MS has also been combined in a multiomic approach to investigate plasmid maintenance in bacterial communities …”