Faculty
Harley M.S. Smith
Assistant Professor and Assistant Plant Cell Biologist (Ph.D., 1998, Michigan State University)
Office: 4202B Genomics Building
Phone: (951) 827-2643
Fax: (951) 827-5155
Email: harleys@ucr.edu
Areas of Expertise
- Cell and Developmental Biology
- Genetics
Background
Regulation of Inflorescene Architecture in Arabidopsis
Selected Publications (Bibliography page)
Background
My college education began at Cabrillo Community College in Aptos, CA (www.cabrillo.edu) after leaving the construction business to pursue my interests in biology. I transferred to the University of California, San Diego (www.ucsd.edu), where I received a B.S. in Biochemistry and Cellular Biology. I received a Ph.D. in Genetics at Michigan State University in the Department of Energy-Plant Research Laboratory (www.prl.msu.edu). I worked on my thesis project in Dr. Natasha Raikhel’s Laboratory (www.cepceb.ucr.edu/members/raikhel.htm) where I studied the function of a nuclear localization signal receptor, AT-IMPORTIN ALPHA.
After receiving my Ph.D., I pursued post-doctoral studies in plant development in Dr. Sarah Hake’s Laboratory (www.pgec.usda.gov/Hake/SHresearch1.html) at the University of California, Berkeley-USDA Plant Gene Expression Center (www.pgec.usda.gov). My background in cell biology allowed me to bring new approaches to basic problems in plant developmental biology that complemented the genetic approaches used in Dr. Hake’s laboratory. I was awarded a three year Post-doctoral Fellowship from the National Institute of Health (NIH) that involved developing a project to gain insight into the function of the KNOTTED1-like homeobox (KNOX) transcription factors in maize and Arabidopsis. During the first phase of my project, we showed that KNOX proteins form complexes with the BEL1-like ( BELL) family of homeodomain proteins. Studies from our laboratory at the CEPCEB indicate that inflorescence development requires the activities of specific KNOX-BELL heterodimers during reproductive development in Arabidopsis.
Regulation of Inflorescence Architecture in Arabidopsis
Formation of the plant body is dependent upon the activity of self-organizing groups of cells called meristems located at the shoot and root apices. Shoot architecture The focus of my laboratory is to understand the biochemical and developmental functions of these KNOX-BELL heterodimers during inflorescence development. We are utilizing biochemical and proteomic approaches to purify PNY-transcriptional complexes from inflorescence meristems. We are also performing yeast two-hybrid studies to identify proteins that associate with PNY/PNF and STM during inflorescence development. To understand the role of PNY/PNF-STM in floral and internode specification, we are identifying target genes that are regulated by these homeodomain heterodimers. A better understanding of PNY and PNF function could provide the necessary framework to modify plant architecture as well as uncover the molecular mechanisms that regulate morphological diversity during reproductive development in higher plants.
| Figure 1. Distinct patterns of growth are observed during (A) vegetative and (B) inflorescence development. During inflorescence development, the SAM initiates flowers and internodes. The inflorescence also initiates branches that mimic the same pattern as the central shoot. |  |
| Figure 2. This figure displays a cladogram of the 13 Arabidopsis BELL proteins. A maize BELL protein, KIP, is used as the outlying sequence. The Arabidopsis BELL cladogram shows that PNY and PNF are paralogous proteins that may share redundant functions during inflorescence development. |  |
| Figure 3. Inflorescence architecture requires the function of PNY and PNF in Arabidopsis. (A) During inflorescence development, mutations in PNY disrupt early internode patterning events in which shortened internodes are randomly dispersed along the reproductive shoot. (B) Although inflorescence development is normal in pnf plants, (C) pny pnf double mutants display a dramatic phenotype after floral induction in which flowers are not produced and internode development is severely impaired. Unlike flowering time mutants, which prolong the vegetative phase, pny pnf plants initiate axillary branches and produce cauline like-leaves after the floral transition. |  |
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| Figure 5. Inflorescence architecture requires the activities of PNY/PNF-BP and PNY/PNF-STM heterodimers. In this model, all four homeodomain complexes regulate early internode patterning events in the inflorescence meristem. Unlike PNY/PNF-BP heterodimers, PNY/PNF-STM complexes also regulate developmental programs required for floral specification and maintaining boundaries between initiating floral primordia and the inflorescence meristem. Thus, PNY/PNF-BP and PNY/PNF-STM heterodimers regulate early patterning events in the SAM that are essential for inflorescence architecture. |  |