Dmitri A. Nusinow

Dmitri A. Nusinow started at the Danforth Plant Science Center in March 2012 as an Assistant Member and Principle Investigator. Dmitri A. Nusinow received his B.S. in Microbiology and Molecular Genetics from University of California – Los Angeles. He attended graduate school at the University of California – San Francisco where he obtained a Ph.D. in Biochemistry and Molecular Biology. Dmitri studied as a post-doctoral fellow with Steve Kay, first at the Scripps Research Institute, then at the University of California – San Diego, beginning in 2007.

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Research

How do plants know what time it is and what season they are in without a watch or calendar?

Time measurement is critical in biology. Each day the Earth's rotation causes oscillations in light and temperature with a period of approximately 24 hours. Selective pressure has led to the repeated evolution of an entrainable, endogenous timekeeper that permits for the anticipation and measurement of these daily cycles. The circadian clock allows for the resonance of internal and environmental oscillations, providing an adaptive advantage through the coordination of physiology and development with daily and seasonal change. While we monitor our watches to know when to eat, meet, and sleep, plants use their internal clock to anticipate sunrise to prepare to harvest photons, measure day-length for tracking seasonal change and to meter out resources to ensure that energy reserves last throughout the evening.

The Nusinow laboratory is focused on understanding how the circadian clock is integrated with environmental signals to control growth, physiology and development. We use a combination of molecular, biochemical, genetic, genomic, and proteomic tools to uncover the molecular connections between signaling networks, the circadian oscillator, and specific outputs (e.g. growth, photosynthesis, photoperiodism, starch accumulation, and defense). Through combining these methods with a comparative proteomics approach, we aim to leverage the knowledge gained from the model plant Arabidopsis to other plant species. Our increased understanding of the mechanisms underlying growth and development will help improve their use as feed, food, and fuel stocks.

Dissecting the function of the circadian clock in growth, timing and development

We have recently identified a multi-protein complex in Arabidopsis, named the "Evening Complex", that is critical for growth, circadian rhythms, and photoperiodism. This transcriptional regulatory complex, composed of EARLYFLOWERING 3, EARLYFLOWERING 4 and LUX ARRHYTHMO, directly participates in the modulation of core clock components, as well as regulates growth through controlling the temporal expression of growth promoting transcription factors, PHYTOCHROME INTERACTING FACTOR 4 and PHYTOCHROME INTERACTING FACTOR 5. The Evening Complex is regulated by the circadian clock and light, peaking at the transition from light to dark at dusk. The Evening Complex also directly influences input pathways that regulate the circadian clock and other photosensitive networks through interaction with components of light signaling pathways (phytochromes and CONSTITUTIVELY PHOTOMORPHOGENIC 1). By studying how this complex functions, we aim to gain an understanding of how the clock and light interact to regulate plant growth, physiology and development.

The molecular mechanism by which the Evening Complex regulates plant growth and development is poorly understood. We are using biochemical purification techniques in combination with mass spectrometry at the Proteomics and Mass Spectrometry Facility to characterize and quantify the composition of the Evening Complex. Using a novel set of affinity purification reagents, we can generate highly purified complexes from different times of day or under specific light conditions to analyze this dynamic complex. Also, we are exploring the genomic targets of this complex by chromatin immunoprecipitation followed by high-throughput sequencing. These methods have already yielded novel components as well as unexpected connections to previously identified genes with roles in growth, light signaling, circadian, and photoperiodic pathways. We are combining molecular techniques, genetic analysis, and cell biology methods to explore these new findings to gain a deeper understanding of how the Evening Complex regulates plant growth, physiology, and development. Ultimately, we hope to use this knowledge to improve and increase yield in food and biofuel crops.

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