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. GA, upon binding to its receptor, activates its response pathway by causing rapid degradation of DELLA. DELLA proteins are likely to function as transcriptional regulators and recent studies identified several key regulatory genes that are targets of DELLA in the model plant Arabidopsis. Two of these genes, one encodes transcription regulator (SCL3) and the other encodes an enzyme (RING) that may regulate stability of its downstream target protein(s). Genetic, molecular and biochemical approaches will be taken to investigate functions of SCL3 and RING in GA-regulated plant growth and development. 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 four undergraduate courses (including one lab course) 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.
Phytohormone gibberellin (GA)-induced growth and development is modulated by DELLA proteins, which are master growth regulators in plants. GA and DELLA play pivotal roles in controlling plant height in crops. Genetic mutations that affect either GA production or DELLA function resulted in the semi-dwarf cultivars of rice and wheat that were the major contributors of the so-called "Green Revolution" in the 1960s. Because of the central role of GA in plant growth, the GA signaling pathway has been studied extensively in the past several decades. Recent molecular and structure studies demonstrated that GA, upon binding to its receptor GID1, activates its signaling pathway by targeting rapid degradation of DELLA, via the ubiquitin-proteasome pathway. Although the early events of GA signaling have been elucidated, it is still largely unknown how DELLAs function to modulate plant growth. In this study, we have elucidated the functions of three DELLA target genes. Our work reveals that DELLAs mediate crosstalks among GA and several other pathways to control plant growth and development. These findings not only contribute significantly toward the basic knowledge of plant growth mechanisms, but also provide important clues for developing strategies for modulating crop growth. This project helped to train 3 postdoctoral fellows and 4 undergraduate students.
