Lecture 5c: Oomycota Flashcards
Characteristics
- Watermolds, but they are terrestrial
- Hyphae have no cross-walls
- Sexual and asexual reproduction
- oospores-sexual
- flagellated zoospores- asexual
- saprophytic and pathogenic lifestyle
Diploid dominated hapless phase
Phytophthora
- plant destroyer
- plant pathogens
How do zoospores move?
Plants emit concentration of chemicals that attract the zoospores and aid in targeting optimal infection sites
Pattern swimming/ auto-aggregation
Adapted motion of zoospores. Is a result of bio-convection and chemotaxis
How do zoospores attach to host
- they position themselves with their ventral surface facing the plant
- They detach their flagella and secret adhesive material
- Cellulosic cell wall is formed
Penetration of the host
As soon as encystment takes place a new set of mRNA and protein synthesis is triggered to enable penetration. Germ tube emerges close to plant and grows chemotropically towards a suitable penetration site. Hyphae secrete cell wall degrading enzymes.
Where does germination take place?
At the ventral surface of the cyst
Acquiring nutrients for pathogen growth ad reproduction
- colonisation depends on the specific lifestyle of the pathogen. In compatible interactions , successful colonisation culminates in sporulation on the plant surface
Biographic species
Nutrients are acquired through formation of haustoria in the mesophyll cells or cordial cells
Necrotrophic species
Hyphae grow inter or intracellularly acquiring nutrients from dead and dying cells
Effector proteins
Secreted proteins that can alter the host and thereby advance the infection process
Apoplectic effectors
*extracellular
* Located at the interface between the host and the pathogen and function outside the host cell
Cytoplasmic effectors
- intercellular
- Are able to translocate into the host cells and interfere with the defence responses of the host
