Significance of siderophore-producing cyanobacteria on enhancing iron uptake potentiality of maize plants grown under iron-deficiency

Background: In response to iron deficiency and other environmental stressors, cyanobacteria producing siderophores can help in ameliorating plant stress and enhancing growth physiological and biochemical processes. The objective of this work was to screen the potential of Arthrospira platensis, Pseudanabaena limnetica, Nostoc carneum, and Synechococcus mundulus for siderophore production to select the most promising isolate, then to examine the potentiality of the isolated siderophore in promoting Zea mays seedling growth in an iron-limited environment.

Results: Data of the screening experiment illustrated that Synechococcus mundulus significantly recorded the maximum highest siderophore production (78 ± 2%) while the minimum production was recorded by Nostoc carneum (24.67 ± 0.58%). Therefore, Synechococcus mundulus was chosen for the beneficiary study and the intended agricultural application. Siderophore-type identification tests proved that Synechococcus mundulus produced hydroxamate-type. The response surface approach was successful in optimizing the conditions of siderophore production in Synechococcus mundulus with actual values for maximum biomass (387.11 mg L^{- 1}) and siderophore production (91.84%) higher than the predicted values. The proton nuclear magnetic resonance (¹H NMR) analysis data and the Fourier transformer-infrared spectrum analysis (FT-IR) signify the hydroxamate nature of Synechococcus mundulus isolated siderophore. Zea mays seedlings' growth response in the hydroponic system was significantly stimulated in response to supplementation with Synechococcus mundulus siderophore in the absence of iron compared to plants grown without iron and the positive controls. Additionally, the contents of chlorophyll a, chlorophyll b, carotenoids, total carbohydrates, and total protein were all surpassed in siderophore-treated plants, which is expected due to the increased iron content.

Conclusions: The results introduced in this study highlighted the significant potential of Synechococcus mundulus-derived siderophore in stimulating Zea mays physicochemical growth parameters and iron uptake. Findings of this study present novel visions of cyanobacteria producing siderophores as an ecofriendly alternative candidate to synthetic iron chelators and their role in plant stress management.