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
What is the role of trichomes in the phyllosphere? (3)
- Trichomes provide physical protection against environmental stresses
- They help deter or attract specific insects (glandular trichomes)
- Trichomes also enrich specific microbes with currently unknown functions
What do plant seeds harbor in terms of microbial communities?
Bacteria, fungi, and archaea on their surface, as well as endophytes inside
- Once the plant germinates, they can improve growth or protect their host against pathogens.
What affects plant seed composition and the seed microbiome? (4)
- Seeds typically harbor tens to hundreds of microbial species
- The plant genotype shapes the seed microbiota
- Environmental factors and agricultural practices strongly influence the seed microbiome
The seed microbiome can be vertically transmitted from one plant generation to the next
