Department of Crop Sciences University of Illinois at Urbana-Champaign

Agronomy Day 2006

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Uncoupling FUSCA 3 from other seed developmental factors reveals its critical function in oil deposition

Hongyun Wang, Young Sun Jung, Jinhua Guo, and Yun Lin1

Department of Crop Sciences, University of Illinois, Urbana, IL 61801
1Yun Lin, assistant professor, yunlin@illinois.edu, 2443543

Plants accumulate large amounts of oil, protein, and starch into their seeds. These compounds are not only essential nutrients for human and livestock, but also raw materials for many manufactured products such as fibers, inks, lubricants, plastics, and biofuel. The process of storage reserve deposition is an integrated part of seed development. Therefore, understanding how plants control the storage process partly lies in understanding how they control seed differentiation. The development of Arabidopsis seed is likely determined by a few master transcription factors, LEAFY COTYLEDON 1 (LEC1), LEAFY COTYLEDON 2 (LEC2), FUSCA 3 (FUS3), ABSCISIC ACID INSENSITIVE 3 (ABI3), and ABSCISIC ACID INSENSITIVE 5 (ABI5), which are expressed sequentially and together cover the entire seed filling period. To understand how these factors interact to define the timing patterns of each other, and to differentiate their direct and indirect (through a later factor) outputs, we perturbed their expression time course to observe causal relationships. These experiments indicate that the deposition of oil is under the positive control of the master seed transcription factor FUS3. Using transgenic Arabidopsis expressing dexamethasone inducible FUS3, we show further that FUS3 can induce oil biosynthesis gene transcripts ectopically. Our results together with previous observations by others suggest that important seed traits are partitioned among major transcription factors, which opens up new opportunities for crop seed improvement through genetic engineering.