Date of Award
Doctor of Philosophy
Genetics, Development and Cell Biology
Philip W. Becraft
In grass species, the endosperm is a major source of food, feed and industrial raw materials. In maize, the aleurone is the peripheral cell layer of the endosperm that functions primarily as a digestive tissue. The aluerone layer of the endosperm is an excellent system to study cell differentiation and fate specification. Aleurone identity is not fixed and positional cues are continuously required during development to specify and maintain aleurone cell fate in the peripheral layer. A putative genetic hierarchy is proposed based on the collections of aleurone mutants. Cell fate mutants define early factors and aluerone differentiation mutants define factors late in the aleurone development. CRINKLY4 (CR4), a plant receptor-kinase defines an early step in aleurone cell fate and VIVIPAROUS1 (VP1), a B3 domain -containing transcription factor that regulates seed maturation in maize. The intermediate steps between CR4 mediated cell fate specification and Vp1 transcriptions are unknown.CSN5 subunit of the COP9Siganalosome (CSN) interacts with the cytoplasmic domain of Arabidopsis CR4 (ACR4).The kinase domain of ACR4 was shown to bind and phosphorylate the CSN5 subunits in-vitro. In-vivo FRET experiments confirmed that ACR4 was in close proximity to CSN5 within the context of a plant cell. Curcumin treatment (COP9 signalosome inhibitor) of transgenic plants resulted in the accumulation of ACR4-GFP. ACR4-GFP accumulated in a csn5 double mutant suggesting the role of the CSN complex in the turnover of ACR4 receptor. To better understand the transcriptional regulation of the Vp1 and identify upstream candidates in the seed maturation and dormancy process, transfactors that bind to the CE1L element of Vp1 was identified. CE1LBP1, a novel zinc binding protein present in all angiosperms appears to be single copy in maize. Electrophoretic mobility shift assays (EMSAs) with recombinant CE1LBP1 protein and supershift EMSAs using maize embryos nuclear proteins with CE1LBP1 specific antibodies confirmed binding. This study enhances our understanding of cell fate specification and maturation processes that operate in the aleurone cells during cereal grain development.
Antony Mathai Chettoor
Chettoor, Antony Mathai, "Regulation of aleurone cell fate determinants in Zea mays" (2009). Graduate Theses and Dissertations. 10706.