Table 3.
Examples of mechanisms of plant growth promotion by PGPB.
| Gene/Product | Function | Species | Reference |
|---|---|---|---|
| 2,3-butanediol dehydrogenase | - synthesis of 2,3-butanediol - growth promotion - induction of ISR |
Bacillus sp., Aerobacter sp., Serratia sp., Enterobacter sp., Klebsiella sp. | [253] |
| acdS/ACC deaminase | - degradation of ethylene precursor and protects against elevated ethylene levels - ameliorates stress effects |
Azospirillum sp. Pseudomonas putida | [254,255] |
| alkaline phosphatase | - increased P availability via phosphates solubilization | Pseudomonas brassicacearum | [253] |
| bud operon | - synthesis of acetoine and 2,3-butanediol - induction of ISR (induced systemic resistance) - increased drought tolerance |
Enterobacter sp638 | [256] |
| chitinase; glucanase | - defense against fungal pathogens |
Pseudomonas aureginosa, Pseudomonas veronii |
[257,258] |
| exoprotease | - N acquisition - protection against pathogens |
Pseudomonas brassicacearum | [253] |
| fur/transcription factor | - modulates gene expression encoding Fe transporter - Fe acquisition |
Pseudomonas brassicacearum | [253] |
| gcd/pyrroloquinoline quinone (PQQ)-dependant dehydrogenase | - production of gluconic acid - P acquisition |
Pseudomonas fluorescens F113, Erwinia herbicola, Enterobacter intermedium | [253] |
| hcnABC/HCN synthase | - protection against pathogens | Pseudomonas fluorescens. Pseudomonas aeruginosa, Pseudomonas chlororaphis | [259] |
| ilvHI; ivlC/acetohydroxyacid synthase; ketol-acid reductoisomerase | - synthesis of secondary metabolites including antibiotics - induction of ISR |
Bacillus subtilis | [253] |
|
ipd; ppd /indole-3-pyruvate decarboxylase; phenylpyruvate fenylopirogronian decarboxylase |
- synthesis of IAA - promotion of root growth |
Azospirllum brasilense Sp245, Enterobacter cloacae UW5, Enterobacteriaceae | [260,261,262] |
| nagA/N-acetylglucosamine-6 phosphate deacetylase | - chitinase-like protein and defense against fungal pathogens | Pseudomonas brassicacearum | [253] |
| nif/nitrogenase | - nitrogen assimilation |
Azospirllum, Burkoholderia, Rhizobium, Bradyrhizobium, Mesorhizobium,
Delftia, Stenotrophomonas, Rhizobium, Brevundimonas, Variovorax, Achromobacter, Novosphingobium, Comamonas |
[263,264,265,266] |
| phl operon | - production of antibiotic 2,4-diacetylphloroglucinol - induction of ISR |
Pseudomonas fluorescens F113, Pseudomonas protegnes CHA0 | [267] |
| phyC/phytase | - increased P availability via solubilization of inositol | Pseudomonas brassicacearum | [253] |
| rhb; rhtA/siderophore synthase; mebrane Fe-regulated receptor | - production of rhziobactin (siderophore) and Fe acquisition - Fe uptake regulation |
Sinorhizobium meliloti | [268] |
| ribC/riboflavin synthase | - growth promotion - defense against pathogens via ISR - upregulation of pathogenesis-related genes |
Pseudomonas yamanorum | [269] |
| yecA; speB/polyamine permease; agmatinase | - synthesis and/or secretion of polyamines - lowers ethylene level in root cells - modulation of expansin genes expression - promotion of root growth - increases tolerance to low pH, oxidative and osmotic stress |
Bacillus subtilis OKB105 | [270] |