Lon Kaufman, PhD
Light-regulated gene expression and light-regulated signal transduction mechanisms in plants
We use modern molecular, biochemical, and genetic methods coupled with classic photobiological techniques to identify the components of blue light signaling mechanisms that alter gene expression. Blue light is an ancient and ubiquitous regulator of growth and development and examples of blue-light-regulated development are found in all kingdoms. We use the plant model genetic system Arabidopsis thaliana . We currently have two major projects in the lab: 1) Identification of the components of all the pathways that comprise the blue low fluence system - a set of G-protein mediated pathways that have many effects including altered nuclear transcription and increased phenylalanine production, and 2) Identification of the components of the blue high fluence system - a totally separate pathway that leads to the specific destabilization of certain nuclear coded transcripts.
The Blue Low Fluence (BLF) System
Irradiation of seedlings with a single pulse of blue light equivalent to 1 sec of moonlight activates a classic seven trans-membrane segment spanning receptor and G-Protein that make up the first two steps in the BLF-System. The G-protein in turn interacts with at least three effector systems. The first is a Raf-like kinase about which we know very little other than it has a role in early development. The second is prephenate dehydratase, an enzyme responsible for the specific production of phenylalanine. It turns out that the BLF System plays a major role in the synthesis of many plant compounds that derive from Phenylalanine. Last, it interacts with Pirin, a protein that translocates to the nucleus, and in turn effects NF-Y (also known as CCAAT-box binding protein)-mediated gene expression. We are actively studying the role of the BLF-System in gene expression and have identified several of the NF-Y components and DNA sequences that have a role in BLF-System-mediated transcription.;
The Blue High Fluence (BHF) System
Excitation of seedlings with a single pulse of blue light equivalent to two seconds of full sunlight results in the specific degradation of certain nuclear coded transcripts. The receptor for this response is PHOT1 (also responsible for plant bending towards blue light). The RNA destabilization sequence is unique in that it resides in the 5'-UTR of the affected transcripts. The RNA degradation is rapid, occurs on the polysomes, and involves an F-box protein.
Plant cellular stress
Another project started by Dr. K. Warpeha in the lab is to examine some of the features of cellular stress as mediated by G-proteins. This NSF-funded work is focused on abiotic stress and the signaling that occurs in higher plants. In particular, we study phenylalanine and how it affects acclimation and protection from abiotic stressors in Arabidopsis . We have also expanded some features of the work to soybean ( Glycine max L.) and other crop plants. Prephenate dehydratase1 (PD1, a.k.a. ADT3) catalyzes the penultimate step of phenylalanine synthesis in etiolated seedlings of Arabidopsis . A G-protein, GPA1, mediates BL, ABA and UV-A stimulated phenylalanine production which allows for synthesis of protective compounds, epidermal and epicuticular structures. If phenylalanine cannot be synthesized via the PD1 pathway, UV-B and UV-C radiation can cause damage, and can be lethal to the plant, as demonstrated by extensive photobiological characterization of the mutant pd1 . UV-B radiation experienced early in development has statistically significant long-term effects on yield (pods per plant, seed quality), and biomass is also adversely affected.
Warpeha KM and Kaufman LS (2009) UV-effects on young seedlings of soybean: Effects in early development and long-term effects. In: UV Radiation in Global Change: Measurements, Modeling and Effects on Ecosystems . Springer-Verlag and Tsinghua University Press.
Yu XH, Sayegh R, Maymon M, Warpeha K, Klejnot J, Yang HY, Huang J, Lee J, Kaufman L and Lin CT (2008) Light-inducing formation of nuclear bodies of Arabidopsis CRY2 is associated with its degradation in blue light. Plant Cell 21: 118-130.
Warpeha KM, Gibbons J, Carol A, Slusser J, Tree R, Durham W and Kaufman LS (2008) Presence of adequate phenylalanine mediated by G-protein is critical for protection from UV radiation damage in young etiolated Arabidopsis thalianaseedlings. Plant Cell & Environment 31: 1756-1770.
Warpeha KM, Upadhyay S, Yeh J, Adamiak J, Hawkins SI, Lapik YR, Anderson MB and Kaufman LS (2007) The GCR1, GPA1, PRN1, NF-Y signal chain mediates both blue light and ABA responses in Arabidopsis . Plant Physiol 143:1590-1600.
Warpeha KM, Lateef SS , Lapik Y R, Anderson M B, Lee BS and Kaufman LS (2006) G-protein-coupled receptor 1, G-protein G a -subunit 1, and prephenate dehydratase 1 are required for blue light-induced production of phenylalanine in etiolated Arabidopsis . Plant Physiol 140:844-855.
Lapik Y and Kaufman LS (2003) The Arabidopsis cupin domain protein AtPirin1 and AtGPA1, the Arabidopsis Ga subunit interact with each other and regulate seed germination and early seedling development. Plant Cell 15: 1578-1590.
PhD, State University of New York at Stony Brook