Unit 5: Plant and Insect Symbiosis 30

symbiosis

intimate, long-term association between organisms of different species

common arrangement

mulitcellular, eukaryotic host and microbial partner (symbiont)

3 key symbiosis

parasitism, commensalism, mutualism

parasitism

symbiont lower host fitness

commensalism

microbe has no net impact on host fitness

mutualism

symbiont increases host fitness

legumes (seedpods)

plant whose pod can be used in foods

root nodules

small bumps on roots of plants containing microbes

microbes in nodules diazotrophs (N fixation), plants use ammonia for metabolic processes

legume- root nodule symbiosis

microbes on roots fix nitrogen for plant to use, and get hospitable environment, O and C source

mutualism

root nodule formation

1. adhesion

2. secretion/curling

3. invasion

4. threading

5. growth

crown gall disease

plant disease that results in formaiton of tumor on infected plant where bacteria can multiply (parasitism)

Ti (tumor inducing) plasmid

creates T-DNA integrates inot host chromosome

agrobacterium tumefaciens not inherently parasitic...

ability to form tumors and cause disease result of Ti plasmid

T-DNA

encodes expression of plant oncogenes (tumor forming) and expression of noncanonical amino acids (opines)

opines

produced by plant cells via integrated plasmid where serve as source of N and C for bacteria

Vir genes

activated by presence of phenolic compounds released from plant wounds after damage, ensures bacteria targeting susceptible cells

T-DNA transfer

1. nicking of plasmid DNA

2. transfer of T-DNA

3. integration of T-DNA into host cell chromosome

heritable symbionts

some mutually beneficial relationships can be inherited from parent to child

all are obligate symbionts

primary symbionts

required for hsot reproduction or survival

secondary symbionts

not required for host reproduction or survival

bacteriome

organ containing bacteriocytes

bacteriocytes

animal cells containing intracellular bacteria

bacteriocytes are ______

obligate intracellular symbionts and cannot survive outside fo host cell

glassy wing sharpshooter

insect that feeds on xylem of plants

glassy wing nutrient exchange symbiosis

xylem rich in carbs but poor in amino acids, so Baumannia cicadellinicola found in bacterocytes of insects and it synthesizes amino acids for host

endosymbiont genomes

differ substantially from free living bacteria genomes cause of genome reduction

as microbes live inside host, genes are lost, resulting in...

higher AT genome contnet or reduced genome size

higher AT genome content

as spontaneous mutations favor AT over GC

reduced genome size

as non-essential genes lost