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Transcriptomic Response of the Diazotrophic Bacteria Gluconacetobacter diazotrophicus Strain PAL5 to Iron Limitation and Characterization of the fur Regulatory Network. Int J Mol Sci 2022; 23:ijms23158533. [PMID: 35955667 PMCID: PMC9368920 DOI: 10.3390/ijms23158533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 07/27/2022] [Accepted: 07/28/2022] [Indexed: 01/25/2023] Open
Abstract
Gluconacetobacter diazotrophicus has been the focus of several studies aiming to understand the mechanisms behind this endophytic diazotrophic bacterium. The present study is the first global analysis of the early transcriptional response of exponentially growing G. diazotrophicus to iron, an essential cofactor for many enzymes involved in various metabolic pathways. RNA-seq, targeted gene mutagenesis and computational motif discovery tools were used to define the G. diazotrophicusfur regulon. The data analysis showed that genes encoding functions related to iron homeostasis were significantly upregulated in response to iron limitations. Certain genes involved in secondary metabolism were overexpressed under iron-limited conditions. In contrast, it was observed that the expression of genes involved in Fe-S cluster biosynthesis, flagellar biosynthesis and type IV secretion systems were downregulated in an iron-depleted culture medium. Our results support a model that controls transcription in G. diazotrophicus by fur function. The G. diazotrophicusfur protein was able to complement an E. colifur mutant. These results provide new insights into the effects of iron on the metabolism of G. diazotrophicus, as well as demonstrate the essentiality of this micronutrient for the main characteristics of plant growth promotion by G. diazotrophicus.
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Tyrosine Kinase Self-Phosphorylation Controls Exopolysaccharide Biosynthesis in Gluconacetobacter diazotrophicus Strain Pal5. Life (Basel) 2021; 11:life11111231. [PMID: 34833106 PMCID: PMC8620434 DOI: 10.3390/life11111231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 10/28/2021] [Accepted: 11/10/2021] [Indexed: 11/16/2022] Open
Abstract
The biosynthesis of exopolysaccharides (EPSs) is essential for endophytic bacterial colonisation in plants bacause this exopolymer both protects bacterial cells against the defence and oxidative systems of plants and acts on the plant colonisation mechanism in Gluconacetobacter diazotrophicus. The pathway involved in the biosynthesis of bacterial EPS has not been fully elucidated, and several areas related to its molecular regulation mechanisms are still lacking. G. diazotrophicus relies heavily on EPS for survival indirectly by protecting plants from pathogen attack as well as for endophytic maintenance and adhesion in plant tissues. Here, we report that EPS from G. diazotrophicus strain Pal5 is a signal polymer that controls its own biosynthesis. EPS production depends on a bacterial tyrosine (BY) kinase (Wzc) that consists of a component that is able to phosphorylate a glycosyltranferase or to self-phosphorylate. EPS interacts with the extracellular domain of Wzc, which regulates kinase activity. In G. diazotrophicus strains that are deficient in EPS production, the Wzc is rendered inoperative by self-phosphorylation. The presence of EPS promotes the phosphorylation of a glycosyltransferase in the pathway, thus producing EPS. Wzc-mediated self-regulation is an attribute for the control of exopolysaccharide biosynthesis in G. diazotrophicus.
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Leandro MR, Vespoli LDS, Andrade LF, Soares FS, Boechat AL, Pimentel VR, Moreira JR, Passamani LZ, Silveira V, de Souza Filho GA. DegP protease is essential for tolerance to salt stress in the plant growth-promoting bacterium Gluconacetobacter diazotrophicus PAL5. Microbiol Res 2020; 243:126654. [PMID: 33285429 DOI: 10.1016/j.micres.2020.126654] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 11/13/2020] [Accepted: 11/18/2020] [Indexed: 11/19/2022]
Abstract
The use of plant growth-promoting bacteria represents an alternative to the massive use of mineral fertilizers in agriculture. However, some abiotic stresses commonly found in the environment, like salinity, can affect the efficiency of this approach. Here, we investigated the key mechanisms involved in the response of the plant growth-promoting bacterium Gluconacetobacter diazotrophicus to salt stress by using morphological and cell viability analyses, comparative proteomics, and reverse genetics. Our results revealed that the bacteria produce filamentous cells in response to salt at 100 mM and 150 mM NaCl. However, such a response was not observed at higher concentrations, where cell viability was severely affected. Proteomic analysis showed that salt stress modulates proteins involved in several pathways, including iron uptake, outer membrane efflux, osmotic adjustment, cell division and elongation, and protein transport and quality control. Proteomic data also revealed the repression of several extracytoplasmic proteins, especially those located at periplasm and outer membrane. The role of such pathways in the tolerance to salt stress was analyzed by the use of mutant defectives for Δtbdr (iron uptake), ΔmtlK and ΔotsA (compatible solutes synthesis), and ΔdegP (quality control of nascent extracytoplasmic proteins). ΔdegP presented the highest sensitivity to salt stress, Δtbdr, andΔmtlK also showed increased sensitivity, but ΔotsA was not affected. This is the first demonstration that DegP protein, a protease with minor chaperone activity, is essential for tolerance to salt stress in G. diazotrophicus. Our data contribute to a better understanding of the molecular bases that control the bacterial response/tolerance to salt stress, shedding light on quality control of nascent extracytoplasmic proteins.
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Affiliation(s)
- Mariana Ramos Leandro
- Laboratório de Biotecnologia (Setor de Biologia Integrativa), Universidade Estadual do Norte, Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, Campos dos Goytacazes, Rio de Janeiro, Brazil
| | - Luciano de Souza Vespoli
- Laboratório de Biotecnologia (Setor de Biologia Integrativa), Universidade Estadual do Norte, Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, Campos dos Goytacazes, Rio de Janeiro, Brazil
| | - Leandro Fernandes Andrade
- Laboratório de Biotecnologia (Setor de Biologia Integrativa), Universidade Estadual do Norte, Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, Campos dos Goytacazes, Rio de Janeiro, Brazil
| | - Fabiano Silva Soares
- Laboratório de Biotecnologia (Setor de Biologia Integrativa), Universidade Estadual do Norte, Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, Campos dos Goytacazes, Rio de Janeiro, Brazil
| | - Ana Laura Boechat
- Instituto de Química (Departamento de Bioquímica), Universidade de São Paulo, Av. Prof. Lineu Prestes, 748, São Paulo, SP, Brazil
| | - Vivian Ribeiro Pimentel
- Laboratório de Biotecnologia (Setor de Biologia Integrativa), Universidade Estadual do Norte, Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, Campos dos Goytacazes, Rio de Janeiro, Brazil
| | - Julia Rosa Moreira
- Laboratório de Biotecnologia (Setor de Biologia Integrativa), Universidade Estadual do Norte, Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, Campos dos Goytacazes, Rio de Janeiro, Brazil
| | - Lucas Zanchetta Passamani
- Laboratório de Biotecnologia (Setor de Biologia Integrativa), Universidade Estadual do Norte, Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, Campos dos Goytacazes, Rio de Janeiro, Brazil
| | - Vanildo Silveira
- Laboratório de Biotecnologia (Setor de Biologia Integrativa), Universidade Estadual do Norte, Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, Campos dos Goytacazes, Rio de Janeiro, Brazil
| | - Gonçalo Apolinário de Souza Filho
- Laboratório de Biotecnologia (Setor de Biologia Integrativa), Universidade Estadual do Norte, Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, Campos dos Goytacazes, Rio de Janeiro, Brazil.
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Schwab S, Pessoa CA, de Lima Bergami AA, de Azevedo Figueiredo NL, Dos Santos Teixeira KR, Baldani JI. Isolation and characterization of active promoters from Gluconacetobacter diazotrophicus strain PAL5 using a promoter-trapping plasmid. Arch Microbiol 2016; 198:445-58. [PMID: 26914247 DOI: 10.1007/s00203-016-1203-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 01/18/2016] [Accepted: 02/07/2016] [Indexed: 12/27/2022]
Abstract
Gluconacetobacter diazotrophicus is a nitrogen-fixing, endophytic bacterium that has the potential to promote plant growth and increase yield. Genetically modified strains might get more benefits to host plants, including through expression of useful proteins, such as Cry toxins from B. thuringiensis, or enzymes involved in phytohormone production, proteins with antagonistic activity for phytopathogens, or that improve nutrient utilization by the plant. For that, expression systems for G. diazotrophicus are needed, which requires active promoters fused to foreign (or innate) genes. This article describes the construction of a G. diazotrophicus PAL5 promoter library using a promoter-less lacZ-bearing vector, and the identification of six active promoters through β-galactosidase activity assays, sequencing and localization in the bacterial genome. The characterized promoters, which are located on distinct regions of the bacterial genome and encoding either sense or antisense transcripts, present variable expression strengths and might be used in the future for expressing useful proteins.
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Affiliation(s)
- Stefan Schwab
- Embrapa Agrobiologia, Rodovia BR 465 km 7, Seropédica, RJ, Brazil.
| | - Cristiane Alves Pessoa
- Embrapa Agrobiologia, Rodovia BR 465 km 7, Seropédica, RJ, Brazil
- Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Cidade Universitária, Rio de Janeiro, RJ, Brazil
| | - Amanda Aparecida de Lima Bergami
- Embrapa Agrobiologia, Rodovia BR 465 km 7, Seropédica, RJ, Brazil
- Instituto de Tecnologia, Universidade Federal Rural do Rio de Janeiro, Rodovia BR 465 km 7, Seropédica, RJ, Brazil
| | - Nathália Lima de Azevedo Figueiredo
- Embrapa Agrobiologia, Rodovia BR 465 km 7, Seropédica, RJ, Brazil
- Instituto de Agronomia, Universidade Federal Rural do Rio de Janeiro, Rodovia BR 465 km 7, Seropédica, RJ, Brazil
| | | | - José Ivo Baldani
- Embrapa Agrobiologia, Rodovia BR 465 km 7, Seropédica, RJ, Brazil
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