TC - Plant Microbiome Above Ground I Flashcards
What are the main components of the Phyllosphere Microbiome? (2)
- Mostly consists of bacteria (the prevailing component), fungi, and archaea
- Microbes colonize leaf surfaces but can also occur inside plant tissues (endophytes)
How do Phyllosphere (3) and Rhizosphere (3) environments compare?
Phyllosphere:
- Colonized by 10^4 to 10^7 cells/g plant material
- Nutrient-poor and harsh for microorganisms
- Plants release waste products via stomata
Rhizosphere:
- Colonized by 10^9 to 10^11 cells/g rhizosphere soil
- Nutrient-rich environment
- Plants release >20% of their photosynthetically produced carbon compounds via root exudation
What has been the historical focus of plant-microbe interaction research? (3)
Focused on plant-pathogenic microorganisms
- These microorganisms cause significant agricultural damage
Example: The Great Famine in Ireland led to around 1 million deaths and over 1 million emigrating
What are some key features of Plant Diseases? (3)
- Caused by diverse pathogens
- Chemical pesticides are primarily used for control
- Pesticides can harm the environment and human health (e.g. carcinogens)
What is the role of plant-associated microorganisms? (2)
- Most are neutral or beneficial
- Microbiome research identifies these microorganisms and their roles in the plant holobiont
What are some beneficial functions of the plant microbiome? (6)
- Antagonise pathogens
- Enhance growth and support germination
- Stimulate the native immune system
- Enable growth under harsh conditions
- Provide nutrients and rare elements
- Protect against abiotic stress
Which plant microbiomes are mostly studied? (3)
- Focused on plants important for human consumption (e.g. cereals, fruits, vegetables)
- Cereal crops are among the most studied
- More studies are done on plants with larger global cultivation areas
Which plant compartments are mostly studied? (3)
- Belowground microbiomes are studied the most due to higher microorganism densities.
- Aboveground microbiomes are less studied due to technological limitations.
- The seed microbiome is particularly understudied
What are the current challenges in phyllosphere microbiome research? (3)
- Phyllosphere has lower microbial biomass, making extraction harder
- Extracted material often contains more host plant material than microbes
- Microbial community dynamics are higher in the phyllosphere than in the rhizosphere
What environmental factors make the phyllosphere an extreme habitat? (5)
- Low nutrient availability
- High UV radiation
- Temperature fluctuations
- Fluctuations in humidity
- Competition between microorganisms
What role do stomata play in the phyllosphere? (3)
- Used by plants for gas exchange and to release waste products
- Microbial metabolites can enter the plant and elicit various responses
- Some beneficial bacteria accumulate near stomata (Paraburkholderia dioscoreae Msb3, a phyllosphere symbiont, colonizes the tomato phyllosphere and promotes plant growth by action of its ACC deaminase.)
What is 1-aminocyclopropane-1-carboxylate (ACC) important for in plants? (3)
Functions as a precursor to ethylene, a hormone important for:
- Fruit ripening
- Flowering
- Stress responses
When ACC is converted to ethylene what happens? (6)
Reduces:
- Biomass
- Photosynthesis
- Protein content
- Activation of stress-responsive genes
- Soil adherence
- Yield
When ACC forms the byproducts ammonia and butyrate what happens? (6)
Increases:
- Biomass
- Photosynthesis
- Protein content
- Activation of stress-responsive genes
- Soil adherence
- Yield
How do stomata play a role in plant infections? (4)
- Stomata serve as entry points for various pathogens to infect plants
- Phyllosphere microbiota can prevent infections via stomata
- Prevention is based on niche competition, where beneficial/neutral microbes compete with pathogens for space
- Beneficial microbes may also inhibit pathogens by producing antimicrobial compounds or interfering with virulence signaling needed for infection
