PP875 - Plant Virology
Course Instructors
Tom German and Amy Charkowski
Course Objectives
Students will gain an understanding of plant virus replication and movement, vectors that spread plant viruses, and how plants resist virus infection. Control and detection methods for plant viruses and how plant viruses are used as tools to examine plant biology will also be discussed.
Class Format
This will be a lecture/discussion/hands-on course that is schedule to meet for two hours once per week. Additional out of class time will be required to complete lab projects.
Assignments and Grading
Students are expected to attend each class and participate in discussion during lecture and laboratory portions of the class (15%).
Students will keep a laboratory notebook to describe lab exercises (20%). This lab notebook is expected to clearly describe the purpose of the exercise, the methods used, the results, and a discussion of the results. The majority of lab exercises will take place during class time. However, as part of this course, students will purify a plant virus and must set up laboratory time with Dr. German for virus purification.
Students will prepare a two page (single spaced, 12 point font) extension article describing an agriculturally important plant virus (20%). This assignment will be anonymously critiqued by the class. After the critique, students will then re-write the article and include a paragraph assessing how their statement has improved.
Questions based on the lecture or reading will be assigned at the end of lecture each week. Students will prepare a one paragraph answer and email it to the instructors prior to the next class meeting (15%).
Students will be divided into four groups and will prepare 30 minute presentations on the life cycle, epidemiology, vectors, and control measures for an important plant virus (30%).
Virus Purification Groups
TMV = Fanhong and Ismail
TSWV = Chakradhur, Emily, and Michelle
CMV = Trisha and Jon
PVY = Shahideh and Ken
Virus Presentation Groups
CEVd = Fanhong and Ismail
CTV = Chakradhur and Emily
WSSMV = Trisha and Jon
PPV = Shahideh and Ken
CYVV = Michelle
Lecture: Signs and symptoms of plant diseases caused by viruses, Economic losses caused by viruses, Examples of significant plant virus epidemics No Lab Reading assignment: Harrison and Adkins and Kamenova Other suggested reading: Fargette and Scholthof and Zaitlin Lecture Question: (answer one of the two) 1. Define these terms used to describe virus symptoms: mosaic, chlorosis, necrosis, rugousity, vein-clearing, calico, stunting, variegation, local lesion 2. Define and explain how the following types of hosts are used by virologists: maintenance host, purification host, local lesion host, diagnostic host Jan 31 Lecture: Virus structure, replication, genome organization, gene expression strategies; plus strand viruses Lab: Purposes: 1. Mechanical transmission of TMV to Nicotiana tabacum nn and N. tabacum NN plants. 2. Mechanical transmission of TSWV to Nicotiana glutinosa plants. 3. Test four potato viruses (PVY, PVS, PVX, and PLRV) for mechanical transmission to potato. 4. Determine if PVY and PVX or PVY and PVS have synergistic interactions in potato. Methods: Buffers used with each virus? Dilutions made with inoculum? Viruses inoculated onto which plants? Viruses were inoculated with which method? Reading assignment: Noueiry and Ahlquist Other suggested reading: Culver Lecture Question: In our laboratory exercise on Jan 31, we worked with several different viruses, including TMV, TSWV, PVY, PVX, PVS, and PLRV. Descriptions of these viruses can be found in reserved books in the Plant Pathology library or at this site: Plant Viruses Online Describe the following attributes of each of these viruses (an example is given for PVY): Full Name: Potato virus Y Family: Potyviridae Shape: flexuous rods; helical Genome size and type: plus-sense linear ssRNA; unipartite; 10.4 kb in size Transmission: aphid transmitted and mechanically transmitted Lecture: Virus structure, genome organization, gene expression strategies; minus strand viruses Lecture Question: Positive-strand RNA viruses that do not have the 5’cap and 3’poly(A) tail structure characteristic of eukaryotic mRNAs have evolved various mechanisms to ensure that translational initiation can proceed in a manner analogous to that of the normal cellular mRNA. Describe, in your own words, an example of how a viral RNA without a poly a tail can form the translational initiation complex in spite of this difference from “typical” host RNA. Lab: Examine plants for local lesions and symptoms and record results. Reading assignment: Rojas et al. and Dreher and Miller Other suggested reading: Harper et al. and MacDiarmid Lecture: DNA viruses and negative strand viruses Lecture question: In the last several classes periods we have discussed examples of some of the various strategies used by positive-sense RNA plant viruses to express the genes encoded in their genomic RNAs. Choose two viruses in different taxonomic groups and compare and contrast their genomic expression strategies. Lab: Examine inoculated plants for symptoms, concept of phloem-limited viruses and concept of synergy. Discuss inoculation of plants for virus purifications. Reading assignment: Rao Other suggested reading: Bol and Callaway et al. Lecture: Viral movement Lecture question:In this class we discussed examples of some of the various strategies used by negative-sense RNA plant viruses and DNA plant viruses to replicate and express the genes encoded in their genomic RNAs. Describe one aspect of virus replication or gene expression that is unique to negative-sense RNA plant viruses and one aspect unique to DNA plant viruses in comparison to positive-sense RNA plant viruses. Lab: Examine virus-transmitting nematodes Reading assignment: Other suggested reading: Culver and Padmanabhan Lecture: Viral movement Lab: Observe nematodes that are virus vectors. Reading assignment: Ng and Falk SLIDES - Negative Sense Viruses SLIDES - Geminiviruses Mar 6 Lecture: Plant resistance, R-genes, silencing, recessive resistance genes, transgenic strategies Lab: ELISAs of inoculated plants SLIDES - Virus resistance mechanisms Lecture:Guest lecture - Doug Maxwell speaking on control of geminiviruses No Lab Reading assignment: Fuchs and Gonsalves and Kang et al. Other suggested reading: Tepfer Lecture: Vector transmission of plant viruses Lab: Vector transmission experiment Reading assignment: Boonham et al. Lecture: Virus detection methods Lab: Discussion of virus purification methods Be prepared with a virus talk outline for this week. Lecture: Viroids, Satellites, and DI RNAs No lab Reading assignment: Flores et al. and Simon et al. Apr 17 Lecture: Control of plant viral diseases, cultural practices No lab Chakradhar and Emily - Citrus tristeza virus Shahideh and Ken - Plum plox virus Fanhong Meng and Ismail Badillo - CEVd presentation Jon and Trisha - Wheat Spindle Streak Mosaic Virus Lecture: Viruses as tools in plant biology No lab Reading assignment: Lindbo and Dougherty
Jan 24
Feb 7
Feb 14
Feb 21
Feb 28
Mar 13
Mar 20
Spring Break
Mar 27
Apr 3
Apr 10
Apr 24
May 1
May 8
Virology Lingo
A short description of how epifluorescence microscopy works: Epifluorescence
Some descriptions of how confocal microscopy works: confocal
Other Links