"Metagenomic Identification of Candidate Iron-Acquisition Genes in the Cowpea Rhizosphere: Extension Implications for Sustainable Production"

Nutrient availability is critical to the growth, development, and productivity of cowpea (Vigna unguiculata L. Walp); however, iron — like several other essential elements — is often present in soil in forms poorly available for plant uptake. Farmers consequently rely heavily on synthetic fertilizers and other chemical inputs, whose continuous and inappropriate use may adversely affect soil health and the environment. Microbial-based nutrient mobilization offers a potentially sustainable alternative, while agricultural extension can facilitate farmers’ awareness and adoption of such technologies. This study characterized rhizosphere microorganisms associated with cowpea grown at Iresa-pupa, Surulere Local Government Area, Ogbomoso, Oyo State, Nigeria, across the two local cropping seasons — the rain-fed (“winter”, WS) and dry (“summer”, SS) seasons — with emphasis on genes involved in iron acquisition, using a culture-independent shotgun high-throughput sequencing approach and in-silico functional annotation. Functional characterization identified several genes and open reading frames (ORFs) associated with iron acquisition and metabolism. The fhuA and ORF AHA_1953 encoded putative ferrichrome-iron receptor proteins associated with siderophore uptake and iron homeostasis, while fur (ORFs b0683, JW0669, PA4764, VAA_03429, VP0833) was associated with ferric-uptake regulation, ferrous-iron binding, and siderophore biosynthesis. Iron-acquisition-related functional diversity and gene richness were both higher in the winter (rain-fed) sample than in the summer (dry) or bulk soil samples. The findings point to candidate rhizobacteria — including Pseudomonas, Bacillus and Escherichia-related taxa carrying these iron-acquisition genes — that could be evaluated as bio-inoculants, and they highlight opportunities for agricultural extension to promote microbial-based soil-fertility technologies through farmer education, demonstration plots, and participatory technology dissemination.

Agricultural extension, cowpea rhizosphere, iron acquisition genes, shotgun metagenomics, sustainable agriculture.

1. AHEMAD, M. & KIBRET, M. 2014. Mechanisms and applications of plant growth promoting rhizobacteria: current perspective. Journal of King Saud University – Science, 26, 1–20. [Google Scholar] [Crossref]

2. ALI, A., KHALID, R., SAFDAR, A., AKRAM, Z. & HAYAT, R. 2015. Characterization of plant growth promoting rhizobacteria isolated from chickpea (Cicer arietinum). British Microbiology Research Journal, 6, 32. [Google Scholar] [Crossref]

3. BEJARANO, A., RAMÍREZ-BAHENA, M.-H., VELÁZQUEZ, E. & PEIX, A. 2014. Vigna unguiculata is nodulated in Spain by endosymbionts of Genisteae legumes and by a new symbiovar (vignae) of the genus Bradyrhizobium. Systematic and Applied Microbiology, 37, 533–540. [Google Scholar] [Crossref]

4. CONSORTIUM, U. 2015. UniProt: a hub for protein information. Nucleic Acids Research, 43, D204–D212. [Google Scholar] [Crossref]

5. ENAGBONMA, B. J. & BABALOLA, O. O. 2023. Metagenomics reveals the microbiome multifunctionalities of environmental importance from termite mound soils. Bioinformatics and Biology Insights, 17. [Google Scholar] [Crossref]

6. ESCOBAR-ZEPEDA, A., VERA-PONCE DE LEON, A. & SANCHEZ-FLORES, A. 2015. The road to metagenomics: from microbiology to DNA sequencing technologies and bioinformatics. Frontiers in Genetics, 6, 348. [Google Scholar] [Crossref]

7. FAHAD, S. 2012. Growth promotion by P-solubilizing, siderophore and bacteriocin producing rhizobacteria in Zea mays L. Journal of Medicinal Plants Research, 6, 553–559. [Google Scholar] [Crossref]

8. FAN, K., CARDONA, C., LI, Y., SHI, Y., XIANG, X., SHEN, C., WANG, H., GILBERT, J. A. & CHU, H. 2017. Rhizosphere-associated bacterial network structure and spatial distribution differ significantly from bulk soil in wheat crop fields. Soil Biology and Biochemistry, 113, 275–284. [Google Scholar] [Crossref]

9. FILLAT, M. F. 2014. The FUR (ferric uptake regulator) superfamily: diversity and versatility of key transcriptional regulators. Archives of Biochemistry and Biophysics, 546, 41–52. [Google Scholar] [Crossref]

10. GI, M., LEE, K.-M., KIM, S. C., YOON, J.-H., YOON, S. S. & CHOI, J. Y. 2015. A novel siderophore system is essential for the growth of Pseudomonas aeruginosa in airway mucus. Scientific Reports, 5, 1–15. [Google Scholar] [Crossref]

11. GKOREZIS, P., DAGHIO, M., FRANZETTI, A., VAN HAMME, J. D., SILLEN, W. & VANGRONSVELD, J. 2016. The interaction between plants and bacteria in the remediation of petroleum hydrocarbons: an environmental perspective. Frontiers in Microbiology, 7, 1836. [Google Scholar] [Crossref]

12. GRESOCK, M. G. & POSTLE, K. 2017. Going through the motions: the ExbB/ExbD/TonB system. Journal of Bacteriology, 199. [Google Scholar] [Crossref]

13. KOBYLARZ, M. J., GRIGG, J. C., SHIN-ICHI, J. T., RAI, D. K., HEINRICHS, D. E. & MURPHY, M. E. 2014. Synthesis of L-2,3-diaminopropionic acid, a siderophore and antibiotic precursor. Chemistry & Biology, 21, 379–388. [Google Scholar] [Crossref]

14. KRANZLER, C., RUDOLF, M., KEREN, N. & SCHLEIFF, E. 2013. Iron in cyanobacteria. Advances in Botanical Research. Elsevier. [Google Scholar] [Crossref]

15. ODELADE, K. A., YAHYA, M., SULAIMON, S. O., ONAOLAPO, A. A. & JACOB, P. C. 2025. Molecular profiling of cowpea rhizospheric microbes using metagenomics sequencing. The Bioscientist Journal, 13(1), 113–130. DOI: 10.54117/the_bioscientist.v13i1.187 [Google Scholar] [Crossref]

16. PAL, R. R., MORE, R. P. & PUROHIT, H. J. 2018. Bioinformatics tools for shotgun metagenomic data analysis. Soft Computing for Biological Systems. Springer. [Google Scholar] [Crossref]

17. SAHA, M., SARKAR, S., SARKAR, B., SHARMA, B. K., BHATTACHARJEE, S. & TRIBEDI, P. 2016. Microbial siderophores and their potential applications: a review. Environmental Science and Pollution Research, 23, 3984–3999. [Google Scholar] [Crossref]

18. UZOH, I. M. & BABALOLA, O. O. 2018. Rhizosphere biodiversity as a premise for application in bio-economy. Agriculture, Ecosystems & Environment, 265, 524–534. [Google Scholar] [Crossref]

19. WELLS, R. M., JONES, C. M., XI, Z., SPEER, A., DANILCHANKA, O., DOORNBOS, K. S., SUN, P., WU, F., TIAN, C. & NIEDERWEIS, M. 2013. Discovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis. PLoS Pathogens, 9. [Google Scholar] [Crossref]

20. XIA, F., ZHOU, X., LIU, Y., LI, Y., BAI, X. & ZHOU, X. 2019. Composition and predictive functional analysis of bacterial communities inhabiting Chinese Cordyceps insight into conserved core microbiome. BMC Microbiology, 19, 105. [Google Scholar] [Crossref]

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