Metabolomic profiling of wild‐type and mutant soybean root nodules using laser‐ablation electrospray ionization mass spectrometry reveals altered metabolism

Abstract

SUMMARY The establishment of the nitrogen‐fixing symbiosis between soybean and Bradyrhizobium japonicum is a complex process. To document the changes in plant metabolism as a result of symbiosis, we utilized laser ablation electrospray ionization‐mass spectrometry (LAESI‐MS) for in situ metabolic profiling of wild‐type nodules, nodules infected with a B. japonicum nifH mutant unable to fix nitrogen, nodules doubly infected by both strains, and nodules formed on plants mutated in the stearoyl‐acyl carrier protein desaturase (sacpd‐c) gene, which were previously shown to have an altered nodule ultrastructure. The results showed that the relative abundance of fatty acids, purines, and lipids was significantly changed in response to the symbiosis. The nifH mutant nodules had elevated levels of jasmonic acid, correlating with signs of nitrogen deprivation. Nodules resulting from the mixed inoculant displayed similar, overlapping metabolic distributions within the sectors of effective (fix+) and ineffective (nifH mutant, fix−) endosymbionts. These data are inconsistent with the notion that plant sanctioning is cell autonomous. Nodules lacking sacpd‐c displayed an elevation of soyasaponins and organic acids in the central necrotic regions. The present study demonstrates the utility of LAESI‐MS for high‐throughput screening of plant phenotypes. Overall, nodules disrupted in the symbiosis were elevated in metabolites related to plant defense.

The Impacts of Domestication and Agricultural Practices on Legume Nutrient Acquisition Through Symbiosis With Rhizobia and Arbuscular Mycorrhizal Fungi

“…Metabolic profiling has been used to study metabolic shifts in SNF associations. Recently, metabolic profiling were performed on effective and ineffective nodules of soybean to identify the active processes according to the partners involved in the symbiosis (Agtuca et al, 2020). Metabolite levels were determined to characterize the different plant phenotypes and interactions with rhizobia.…”

Spatial Mapping of Plant N-Glycosylation Cellular Heterogeneity Inside Soybean Root Nodules Provided Insights Into Legume-Rhizobia Symbiosis

“…These specialized root organs have several visually and functionally distinct compartments (i.e., outer cortex, sclerenchyma, inner cortex, and infection zone), where a population of root cells is infected with nitrogen-fixing soil bacteria (Rhizobiaceae) (Livingston et al, 2019 ). Using the MALDI-MSI (Velickovic et al, 2018 ) and other MSI modalities (Agtuca et al, 2020 ; Samarah et al, 2021 ), we recently spatially resolved critical metabolic and lipidomic pathways in different compartments of soybean root nodules, and also showed different metabolic profiles in infected and uninfected plant cells inside the infection zone (Samarah et al, 2020 ).…”

Improving Bambara Groundnut Production: Insight Into the Role of Omics and Beneficial Bacteria

“…The study reported that the relative abundance of fatty acids, purines, and lipids was changed significantly in response to the symbiosis. Agtuca et al, 2020 analyses of protein levels through proteomics technique are more essential for deciphering complex molecular mechanisms in plant-bacteria associations, especially as it applies to BGNbacteria interactions. Therefore, identification of other proteins involved in plant beneficial interactions through proteomics analysis of BGNbacteria interaction is an avenue to harness the capacity of these beneficial bacteria on BGN yield.…”