Foliar pathogen-induced assemblage of beneficial rhizosphere consortia increases plant defense against Setosphaeria turcica

doi:10.52586/4966

Pseudomonas fluorescens MZ05 Enhances Resistance against Setosphaeria turcica by Mediating Benzoxazinoid Metabolism in the Maize Inbred Line Anke35

Agriculture ◽

10.3390/agriculture10020032 ◽

2020 ◽

Vol 10 (2) ◽

pp. 32 ◽

Cited By ~ 1

Author(s):

Cheng Zhou ◽

Zhongyou Ma ◽

Xiaoming Lu ◽

Lin Zhu ◽

Congsheng Yan

Keyword(s):

Pseudomonas Fluorescens ◽

Expression Profiles ◽

Gene Expression Profiles ◽

Defense Responses ◽

Setosphaeria Turcica ◽

Disease Occurrence ◽

Induced Disease Resistance ◽

Foliar Pathogen ◽

Maize Plants ◽

Leaf Pathogen

Beneficial rhizobacteria can inhibit foliar pathogen infection by activation of defense responses, yet it the mechanisms of rhizobacteria-induced disease resistance remain largely unknown. Here, inoculation of susceptible maize plants with Pseudomonas fluorescens MZ05 significantly reduced disease occurrence caused by the leaf pathogen Setosphaeria turcica. Gene expression profiles of MZ05-inoculated plants were investigated by RNA-sequencing analyses, showing that several differentially expressed genes were positively associated with the metabolic processes of benzoxazinoids. Accordantly, the inoculation with P. fluorescens MZ05 resulted in a significant increase in the levels of 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) in the maize leaves. Furthermore, pre-inoculation with P. fluorescens MZ05 enhanced the transcription of two defense-related marked genes PAL and PR2a, as well as BX2 and GLU2, which are involved in DIMBOA biosynthesis, in pathogen-infected leaves. Defense responses in the inoculated plants were also greatly stronger and quicker than that in non-inoculated plants after pathogen attacks. However, virus-mediated silencing of BX2 or GLU2 remarkably attenuated the MZ05-induced effects, as evidenced by more disease occurrence and lower transcription of PAL and PR2a. Collectively, these findings indicated that the MZ05-induced increases of DIMBOA levels participated in the mediation of priming, which was the key mechanism in the rhizobacteria-induced host resistance.

Download Full-text

Effects of root-colonizing fluorescent Pseudomonas on Arabidopsis resistance against a pathogen and an herbivore

Applied and Environmental Microbiology ◽

10.1128/aem.02831-20 ◽

2021 ◽

Author(s):

Tobias B. Löser ◽

Mark C. Mescher ◽

Consuelo M. De Moraes ◽

Monika Maurhofer

Keyword(s):

Plant Defense ◽

Pseudomonas Syringae ◽

Plant Resistance ◽

Molecular Mechanisms ◽

Pathogen Resistance ◽

Systemic Resistance ◽

Negative Effects ◽

Foliar Pathogen ◽

Microbial Strains ◽

Defense Chemistry

Rhizobacteria in the genus Pseudomonas can enhance plant resistance to a range of pathogens and herbivores. However, resistance to these different classes of plant antagonists is mediated by different molecular mechanisms, and the extent to which induced systemic resistance by Pseudomonas can simultaneously protect plants against both pathogens and herbivores remains unclear. We screened 12 root-colonizing Pseudomonas strains to assess their ability to induce resistance in Arabidopsis thaliana against a foliar pathogen (Pseudomonas syringae DC3000) and a chewing herbivore (Spodoptera littoralis). None of our 12 strains increased plant resistance against herbivory; however, four strains enhanced pathogen resistance, and one of these (Pseudomonas strain P97-38) also made plants more susceptible to herbivory. Phytohormone analyses revealed stronger SA induction in plants colonized by P97-38 (vs controls) following subsequent pathogen infection but weaker induction of JA-mediated defenses following herbivory. We found no effects of P97-38 inoculation on herbivore-relevant nutrients such as sugars and protein, suggesting that the observed enhancement of susceptibility to S. littoralis is due to effects on plant defense chemistry rather than nutrition. These findings suggest that Pseudomonas strains that enhance plant resistance to pathogens may have neutral or negative effects on resistance to herbivores and provide insight into potential mechanisms associated with effects on different classes of plant antagonists. Improved understanding of these effects has potentially important implications for the use of rhizobacteria inoculation in agriculture. Importance Plant-associated microbes have significant potential to enhance agricultural production, for example by enhancing plant resistance to pathogens and pests. Efforts to identify beneficial microbial strains typically focus on a narrow range of desirable plant traits; however, microbial symbionts can have complex effects on plant phenotypes, including susceptibility and resistance to different classes of plant antagonists. We examined the effects of 12 strains of Pseudomonas rhizobacteria on plant (Arabidopsis) resistance to a Lepidopteran herbivore and a foliar pathogen. None of our strains increased plant resistance against herbivory; however, four strains enhanced pathogen resistance, and one of these made plants more susceptible to herbivory (likely via effects on plant defense chemistry). These findings indicate that microbial strains that enhance plant resistance to pathogens can have neutral or negative effects on resistance to herbivores, highlighting potential pitfalls in the application of beneficial rhizobacteria as biocontrol agents.

Download Full-text