Beneficial Effect and Potential Risk of Pantoea on Rice Production

Abstract

Bacteria from the genus Pantoea have been reported to be widely distributed in rice paddy environments with contradictory roles. Some strains promoted rice growth and protected rice from pathogen infection or abiotic stress, but other strain exhibited virulence to rice, even causing severe rice disease. In order to effectively utilize Pantoea in rice production, this paper analyzed the mechanisms underlying beneficial and harmful effects of Pantoea on rice growth. The beneficial effect of Pantoea on rice plants includes growth promotion, abiotic alleviation and disease inhibition. The growth promotion may be mainly attributed to nitrogen-fixation, phosphate solubilization, plant physiological change, the biosynthesis of siderophores, exopolysaccharides, 1-aminocyclopropane-1-carboxylic acid deaminase and phytohormones, including cytokinin, indole-3-acetic acid (IAA), auxins, abscisic acid and gibberellic acid, while the disease inhibition may be mainly due to the induced resistance, nutrient and spatial competition, as well as the production of a variety of antibiotics. The pathogenic mechanism of Pantoea can be mainly attributed to bacterial motility, production of phytohormones such as IAA, quorum sensing-related signal molecules and a series of cell wall-degrading enzymes, while the pathogenicity-related genes of Pantoea include genes encoding plasmids, such as the pPATH plasmid, the hypersensitive response and pathogenicity system, as well as various types of secretion systems, such as T3SS and T6SS. In addition, the existing scientific problems in this field were discussed and future research prospects were proposed.

Keywords: PGPR; Pantoea; disease; rice; stress resilience.

Figure 1

Neighbor-joining phylogeny of Pantoea type strains, based on a concatenated dataset composed of partial atpD, gyrB, infB and rpoB genes using maximum composite likelihood. Nodes show the result of 1000 bootstrap replicates.

Figure 2

Phylogenetic tree of 18 species of Pantoea, based on 120 core genes using maximum composite likelihood. Nodes show the result of 1000 bootstrap replicates by IQ-TREE. Trees and dendrograms were visualized using ggtree and iTOL. Genomes from another strain were selected due to lacking the genomic information of the type strain of P. intestinalis and P. dispersa, while no genome information was available for P. coffeiphila.

Figure 3

Phylogeny tree of P. ananatis strains associated with rice plants based on 120 core genes using maximum composite likelihood. Nodes show the result of 1000 bootstrap replicates by IQ-TREE. Trees and dendrograms were visualized using ggtree and iTOL. PGP: Plant growth promotion.