Regulation of DELLA Activity by Post-Translational Modifications and Complex Formation in Arabidopsis

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Gibberellin (GA) is an important plant growth hormone, which promotes seed germination, leaf expansion, stem elongation and flower development in higher plants. The dwarf cultivars of wheat and rice developed during the Green Revolution in the 60s remarkably increased the grain yields. Recent studies revealed that these cultivars are modified in their GA production or responses to GA, illustrating the important role of this hormone in regulating plant development and in agriculture. GA-promoted growth and development is modulated by DELLA proteins, which are major negative regulators (repressors) of GA responses. Recent work in the PI's laboratory (funded by NSF) has made transforming findings that the GA receptor directly targets DELLA for degradation. There is also evidence suggesting multiple layers of regulation on the DELLA protein activity. DELLA is a master growth repressor, which integrates not only the GA signal, but also other hormone signals as well as biotic and abiotic signals (such as light conditions, pathogens, cold and drought stresses). Although DELLA plays such a pivotal role in regulating plant growth, very little is known about how DELLA activity is regulated. Preliminary data support that protein modifications play important roles in modulating DELLA function. Future research in this project will elucidate the molecular mechanisms involved. Broader Impacts:DELLA proteins are functionally highly conserved in Arabidopsis and in many crop plants. For example, the semi-dwarf wheat cultivars, an essential component of the Green Revolution, contain mutations in the Rht loci that encode DELLA proteins. This study will likely to have a broader impact in improving quality of agricultural crops. In addition, a postdoctoral fellow and four undergraduate students will gain research experience in this project. The findings of this study will be incorporated into three undergraduate courses at Duke University. Students will learn to appreciate how the information gained from studies in a model plant system can be used to improve agriculture practice and benefit society.