Lecture 9: Megastigmus

Question 1

douglas fir

Answer 1

psuedotsuga menzesii
native to western NA
planted exotically in france 
number 1 lumber tree 
500,000 hectares

Question 2

megastigmus spermatrophus

Answer 2

small chakid wasp, major seed parasite of doug fir
first 11 months are spent in seed
1 month to fly and mate

Question 3

megastigmus cont.

Answer 3

35-50 scales with 2 ovules per scale

70-100 potential seed but in france 0-3 seed per cone b/c megastigmus parasitism

Question 4

3 possibilities for an empty seed

Answer 4

no pollination, therefore no fertilization and no embryo

• pollination occurs, embyo, insect lays eggs and hatches = larvae, but eats plant embryo and megagametophyte
• unpollinated and should lead to empty seed but parastized

Question 5

hormone

Answer 5

hormone metabolism of seed/ovule changes after infestation

-hormone profiles the same in all treatments except unpollinated parsitized ovules which plant hormones differ

Question 6

venom

Answer 6

females have venom gland
look at gene expression b/c too small to dissect
has 20 venom glands, 3 highly expressed and one highly expressed in females
asapartylglucosaminadase (AGA)

Question 7

gene exppression

Answer 7

insect manipulates gene expression of plant

downregulates defence and upregulates storage reserve genes