Plant-Microbe Interactions

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  1. *infection of plant wound by Agrobacterium and attachment
    • *plant wound releases phenolic compounds- induces vir gene expression using two component system
    • agrobacterium cell motility is reduced, cellulose fibrils formed to attach to plant and richadhesion protein produced
  2. structure of the Ti plasmid of Agrobacterium tumefaciens
    • T-DNA is the only region actually transferred to the plant
    • vir genes encode proteins essential for T-DNA transfer
  3. processing of T-DNA from Ti plasmid
    • vir expression activated
    • endonuclease nicks Ti plasmid next to T-DNA at T-DNA borders
    • single stranded DNA binding protein binds the single strand of T-DNA and transports it into the plant cell
  4. transfer of T-DNA
    • T4SS required for translocation of T-DNA complex into plant cell
    • thought that the T-DNA travels through the T-pilus
    • autoinducers promote T-DNA transfer
  5. integration of T-DNA into plant genome
    • typically integrates into the host genome as full length T-DNA, one copy
    • fairly random, higher frequency of integration into intergenic regions
    • microsimilarities at insertion sites
  6. *tumorigenesis and production of opines
    • T-DNA carries genes for tumor formation some of which synthesize or alter plant growth hormones auxin and cytokinin and production of modified amino acids called opines
    • *opines are produced by the transformed plant cells and are a source of C and N for the agrobacterium
  7. disarmed Ti plasmid as tool
    • remove genes involved in tumor formation
    • have your gene of interested flanked by T-DNA borders
    • ability to stably express genes of interest in plants - GMOs
  8. *flavonoids
    • plant flavonoids induce expression of nod genes
    • *component of the specificity of the Rhizobia- legume symbiosis
    • activates positive transcriptional regulatory of nod genes
  9. *expression of nod genes
    • nod genes encode proteins that produce nod factors
    • nod factors:
    • induce root hair curling
    • trigger plant cell division
    • another component of specificity
  10. *bacteroid
    • differentiated bacteria
    • nitrogen fixation occurs within it only when genes are expressed
  11. *leghemoglobin
    • binds oxygen to keep it away from nitrogenase
    • expression induced as symbiosis forms
Card Set
Plant-Microbe Interactions
general microbiology midterm 3
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