1. List three parasitic plants belonging to three different evolutionary lineages.
Viscum album - European mistletoe
Striga hermonthica - Hexenkraut (
Cassytha filiformis - Schlingfaden
Rafflesia arnoldii - große Stinkeblume
2. What are the differences between holo- and hemiparasitic plants?
Hemiparasites
Holoparasites
Xylem- Xylem connection
Xylem-Xylem and Phloem-Phloem interactions
Usage of water and nutrients of the host plant
Usage of water, nutriens and photosimilarities (are green)
have to conduct photosynthesis
no phototsynthesis is needed
Triphysaria versicolor, striga hermonthica, Viscum album, Cassytha filiformis
Orobanche awgyptiaca, Rafflesia arnoldii
3. Name one parasitic plant that infects host stems and one that infects host roots.
infects stems: Viscum album - European mistletoe
infects roots: striga hermonthica
4. What is the difference between phloem and xylem?
Xylem
Phloem
Transport from root to shoot
Transport from shoot to root
Transport of water and minerals
Transport of photoassimilates
Dead cells
Living cells with no nucleus
Lignified
Not-lignified
Open
Sieve plates
Not connected to symplast
Connected to symplast
5. Propose two experiments to visualize the transport of solutes from host to parasite?
GFP labelled protein : Expression of GFP in phloem companion cells; GFP is transported into the phloem ––> Phloem-mediates transport
CFDA: from host to pariside, for Xylem
6. Which plant hormone induces the germination of Striga seeds and how is it perceived in plants?
Strigolacton (SL)
The receptor hydrolyses Strigolactone (D14)
The stringolactone reception is similar to wich plant hormon signaling pathway? Describe briefly the mechanism.
Similar to COI1 recognition of Jasmonic acid -> ubiquitination of JAZ by E3 ligase.
SL binds to D 14 receptor
2. Binding leads to conformation change and hydrolysis (clevage) of SL.
Recrutment of a Ubiquitine complex (MAX2-SCF)
Ubiquitination of D53- repressor of SL respone
degredation of the D53- repressor is degreded
SL- responsive genes genes de-repressed= activated
-> Leads to germination
7. Propose two control strategies to contain Striga infestations in the field.
“Suicide germination”
Spray field with stringolactone before planting crop plant
-> causes germination and starvation of striga, because of the absence of a host plant
Host plants with a Igs1 low germination stimulant produce diffrent stringolactones and prevent the stringolactones to germine
8. Name one compound that was shown to induce haustoria in parasitic plants.
DMBQ, derives from lignin
Acetosyringone
9. What is HGT?
Horizontal gene transfer: is the non-sexual movement of of genetic information between genomes. Incoming DNA or RNA can replace existing genes, or can introduce new genes into the genome. (nature paper)
Parasitic plants incorporate DNA from the host
10. How do you interpret Horizontal Gene Transfers (HGTs) of genes with shared predicted functions to parasitic plants belonging to different evolutionary lineages?
Since the parasitic plants belong to different evolutionary lineages, it is certain that they both obtained the genes from the hosts ––> convergent evolution
The genes should be beneficial
11. What is a strong indication that a given HGT event occurred by transfer of DNA and not RNA?
Because of the presence of introns in the genome
no reverse transciptase of the RNA and wouldnt be inherited
12. Name one substance produced by a parasitic plant and perceived by the parasitized host?
Cytokinin
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