1. MYB Family Transcription Factors Jonathan Russell Rena Schweizer Mike Douglas

2. What is a Transcription Factor? Transcription factor – any protein other than RNA Polymerase that is required for transcription

3. MYB Family Myeloblast ---> MYB (came from first identified MYB which was in an avian oncogene) 203 identified MYB-family transcription factors Found in Eukaryotes

4. Our Genes Within the Myb Family Mike Jonathan Mike Rena

5. MYB FAMILY PHYLOGENY What is the Structure and Function of MYBs? Jonathan’s Gene Emily’s Gene

6. What is the Structure of MYB Proteins? All share a conserved MYB DNA- Binding Domain –Up to three imperfect repeats (Helix-Turn-Helix structure) of ~53 AA each –Three regularly spaced tryptophan residues –R1, R2, R3 repeats –Subfamilies are classified by number of adjacent repeats (MYBR1, R2R3- type MYB, MYB3)

7. What Motifs Do Mybs Employ? Helix-turn-Helix structures are crucial to sequence specificity HTH intercalates in major groove Recognition by C- terminal helix

8. MYB Structure: R2R3 Sub Family Largest family characterized in plants Both R2 and R3 required for sequence- specific binding Some redundancy of amino acid sequence, but flexibility in recognition

9. What are the functions of Plant MYB Proteins? Wide diversity of functions By no means fully characterized In general: regulate many aspects of plant metabolism and development But… –Some bind telomeric sequences, structural –Some are clearly transcription factors (from circadian clock to root hair formation)

10. Proposed Plant MYB Functions Vertebrates Cellular proliferation Expressed in actively dividing cells before differentiation Plants Control of secondary metabolism Regulation of cell morphogenesis Serving in signal transduction pathways responding to plant growth regulators

11. Specific MYB Functions Controlling Secondary Metabolism Phenylpropanoid metabolism (modifications of compounds derrived from phenylalinine) One branch resposible for the production of anthocyanins (major group of plant pigments) Regulating Cellular Morphogenesis In petunia, essential for developing the conical form of petal epidermal cells In Arabidopsis, essential for differentiation of hair cells in leaf and stem Signal Transduction Pathways Hormonal responses during seed development and germination In Arabidopsis and maize, activate genes to respond to dehydration and salt stress For all categories, variations across plant species

12. The Future of MYB Experiments In order to characterize each MYB gene, mutation studies need to be performed This involves: knocking out specific genes and looking for resulting phenotypes…