In a potato plant, photosynthesis in the leaves fixes carbon from CO 2 into hexose
sugars, and starch synthesis in the below-ground, non-photosynthetic tubers
store sugars. Explain the ultimate sources and the biochemical or biophysical
forms of free energy (potential) that drive the energy-requiring steps from and
including formation of hexoses in leaves, to and including starch synthesis in
tubers. In particular, explain the direct or indirect way that ATP is involved in the
energetics of each step. Be sure to discuss both the metabolic (biochemical) and
mechanical (physical movement) processes that are involved. You are not
required to draw complete biochemical pathways, but you need to name the
pathways and cycles involved, and briefly describe how they use or yield free
energy. You may use diagrams to help in your explanations, provided that the
diagrams and associated text make specific, clear points.
Answer any three questions from among those listed below. If you wish, you may
use diagrams to clarify your written answers. Be sure to indicate which questions
you are answering, and be sure to write your name on every sheet of your exam.
1. Discuss how glycolysis, pentose phosphate pathway and citric acid cycle
pathways contribute precursors for the formation of secondary metabolites or
chemical signals that participate in plant defense.
2. (A) Briefly discuss the relationships among precursors of gibberellic acid,
auxin, cytokinin and brassinosteroid. (B) Indicate the roles of any two of these
plant hormones in plant defense and their interactions with typical plant defense
pathways.
3. Compare and contrast biotrophs, necrotrophs, and hemibiotrophs. Include in
your answer aspects of their morphology, pathogenicity, and nutritional
requirements.
4. What is the minimal set of genes coded by a plus-stranded RNA virus
necessary for infecting the entire plant (explain the functions of genes) and what
kind of cis-acting RNA elements facilitate virus infections?
5. Provide a list of specific plant pathogens (i.e., taxonomically relevant names)
and state which part of the plant (host cell) endomembrane system they
utilize/hijack. You must list a different pathogen for each endomembrane target.).
6. (A) Describe cell division in FULLY expanded leaves (hint: be brief, this might
be a trick question). (B) Describe a group of pathogens that alters the plant cell
cycle. Why must these pathogens do so?
7. Describe two different mechanisms whereby type III effectors contribute to
disease symptoms in plants.
8. (A) What are the major differences in the ontogeny (i.e., developmental
pathways) of root knot galls versus cyst nematode syncytia? (B) List and
describe the three main types of experiments that have been performed to
address the role of auxin in syncytium/gall development?