L8: Plant Microbiome Flashcards
what functions are present in the plant microbiome
- boost plant health
- control pathogens
- alleviate abiotic stress
- probiotics
- microbiome manipulation
what are the 4 main microhabitats
- Phyllosphere
- Leaf endosphere
- Rhizosphere
- Root endosphere
main microhabitats - which has the most diverse microbial community
the rhizosphere
what are the beneficial effects of the plant microbiome
- alleviate stress
- growth stimulation
- pathogen defense
- nutrient acquisition
beneficial effects - alleviate stress
- detoxification
- Regulate ACC deaminase
- reducing ethylene production
- ROS scavenging
beneficial effects - growth stimulation
Microbes produce plant hormones (auxins, gibberellins, cytokinins)
beneficial effects - pathogen defense
- Antibiotic production
- lytic enzymes
- siderophores
beneficial effects - nutrient acquisition
- Nitrogen fixation
- unlock nutrients
- enhance plant nutrient uptake
factors shaping plant microbiome - above ground
- Plant genotype (genes, physiology)
- Climate (air, precipitation)
- Predators
- Pathogens
- Soil type
factors shaping plant microbiome - below ground
- Soil microbiomes
- Soil pH, moisture, composition
- Genotype (exudates, immunity)
microbiome colonization
- bulk soil: soil composition/ microbial communties
- rhizosphere: plant metabolites and plant-plant interactions
- rhizosphere and endosphere: plant immunity
- improved plant growth
microbiome colonization - plant immunity
- Pattern-triggered immunity (PTI)
- Effector-triggered immunity (ETI)
- Systemic acquired resistance (SAR)
- Induced systemic resistance (ISR)
- Wound-induced defense
- RNA interference (RNAi)
microbiome colonization: plant immunity - pattern-triggered immunity
- plant’s first line of defense against pathogens
- triggered by the recognition of conserved microbial molecules known as pathogen-associated molecular patterns (PAMPs)
microbiome colonization: plant immunity - effector-triggered immunity (ETI)
a more robust and specialized immune response, activated when the plant detects specific pathogen effectors
microbiome colonization: plant immunity - systemic acquired resistance (SAR)
- After local infection, a signal (i.e., salicylic acid) is sent from the infection site to the rest of the plant, “priming” distant tissues to be more resistant to future infections.
- SAR provides long-lasting protection against a broad spectrum of pathogens.
microbiome colonization: plant immunity - Induced systemic resistance (ISR)
- another whole-plant immune response, similar to SAR but triggered by beneficial microbes (such as rhizobacteria) rather than pathogens
- mediated by signaling pathways involving jasmonic acid (JA) and ethylene rather than salicylic acid.
microbiome colonization: plant immunity - Wound-induced defense
A response triggered by tissue damage, such as from feeding insects
microbiome colonization: plant immunity - RNA interference (RNAi)
A defense mechanism against viral infections.
explain the environment below ground
- rhizosphere
- rhizoplane
- endosphere
below ground environment - rhizosphere
- Area of soil around a plant’s root system.
- Extends few millimeters from the root surface into the surrounding soil
below ground environment - rhizoplane
Thin layer of soil that adheres directly to the root surface, including the root epidermis and mucilage
below ground environment - endosphere
Interior of plant tissues, particularly the root, where microbes can reside
below ground microbiome: alpha-diversity - endosphere vs rhizosphere
- endosphere communities had the lowest α-diversity
- rhizosphere had the highest α-diversity.
below ground microbiome: alpha-diversity - bulk soil vs rhizosphere
difference in α-diversity between bulk soil and rhizosphere was not statistically significant
below ground microbiome - beta-diversity
Microbial composition (beta-diversity) was different across microbial compartments
what is Bacterial nodulation
a symbiotic process that occurs when leguminous plants form root nodules in response to bacterial colonization of Rhizobia bacteria
bacterial nodulation - what is Rhizobia
bacteria that can fix nitrogen (N2 to NH3) originally thought to be only members of the genus Rhizobium
bacterial nodulation - root nodules
formed when nitrogen fixing bacteria called rhizobia enter the cells of a host plant
bacterial nodulation - process
- flavonoids
- nodulation factors (NFs)
- Expression of NF
bacterial nodulation process - flavonoids
- Under low N conditions
- the plant will release flavonoids into the rhizosphere
bacterial nodulation process - nodulation factors (NFs)
Flavonoids induce the expression of genes involved in the synthesis of nodulation factors (NFs) in some bacteria
bacterial nodulation process - expression of NFs
Expression of NF activate the development of nodules in the plant
Phosphate solubilizing bacteria (PSB)
group of beneficial microbes that play a critical role in the phosphorus cycle by making insoluble forms of phosphorus (P) available to plants
phosphate solubilizing bacteria (PSB) - Pseudomonas
- Species in this genus are widely recognized for their ability to solubilize phosphate
- Pseudomonas fluorescens, for example, is often used in biofertilizers
phosphate solubilizing bacteria (PSB) - Bacillus
- This genus includes several PSB, such as Bacillus megaterium and Bacillus subtilis.
- They are frequently studied for their efficiency in releasing phosphate through organic acid production.
phosphate solubilizing bacteria - Rhizobium
- Known primarily for nitrogen fixation in legumes
- many species of Rhizobium also exhibit phosphate solubilization capabilities, providing dual benefits to plants
phosphate solubilizing bacteria - Azotobacter
- fix nitrogen
- solubilize phosphate
- promoting plant growth through multiple pathways.
phosphate solubilizing bacteria - Enterobacter
Species such as Enterobacter cloacae are involved in phosphate solubilization and are found in various soil environments
phosphate solubilizing bacteria - Acinetobacter
Some strains of Acinetobacter have been found to solubilize phosphate effectively, contributing to nutrient cycling in soils.
phyllosphere environment
contains epiphytes and endophytes
phyllosphere - epiphytes
microbiota members residing on the surface
phyllosphere - endophytes
- microbiota members that reside inside phyllosphere tissues
- either intracellular spaces and/or within the plant cell
explain microbiome homeostasis on rice leaves
regulated by a precursor molecule of lignin biosynthesis
microbiome homeostasis on rice leaves - knockout mutant
- knockout mutant of OsPAL02 (KO) results in reduced Pseudomonadales abundance
- creates dysbiosis of the phyllosphere microbiota and consequently higher susceptibility of plants to disease
phyllosphere vs rhizosphere sensitivity
- phyllosphere microbiome is more sensitive to anthropogenic disturbance
- this is because it has a lower functional redundancy than the rhizosphere
phyllosphere vs rhizosphere sensitivity - factors that create sensitivity
- temperature
- precipitation/drought
- elevated CO2 levels
- extreme weather events
- invasive species
