Signal Transduction and the Regulation of Organ Abscission in Arabidopsis

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

Abscission in plants is a universally recognized natural phenomenon. It is the product of a developmental process that is programmed to actively shed organs from the body of a plant. Recent results support the role of a signaling pathway from putative ligand to receptor to downstream effectors that control abscission in Arabidopsis thaliana. Alteration in the expression of Inflorescence Deficient in Abscission (IDA), which encodes a predicted secreted small protein, the genes for the receptor-like protein kinases HAESA (HAE) and HAESA-like 2 (HSL2), the Mitogen-Activated Protein Kinase Kinase 4 (MKK4) and MKK5 all show similar loss-of-function abscission-defective phenotypes. Conversely, expression of constitutively active MKKs rescue the abscission defective phenotype of hae hsl2 and ida. Additionally, MAP kinase activity is reduced in the region of the flowers that undergo abscission. Analyses of plants overexpressing IDA in a hae hsl2 background show HAE and HSL2 are epistatic to IDA. Taken together these results suggest IDA, HAE, HSL2, and a MAP kinase cascade function in a common pathway to regulate abscission. The goal of the research is to test the hypothesis there is direct sequential interaction between IDA, HAE, HSL2, and a MAP kinase cascade to regulate the separation of cells in the abscission zone. The first aim is to determine if IDA binds to the HAE and HSL2 receptors in planta and activates these receptors. The second aim is to test candidate MAP kinases and MAP kinase kinase kinases to determine if they function in the abscission signaling cascade. The third aim is to investigate the cellular changes triggered prior to cell separation to begin to understand the processes targeted by the IDA-HAE-MAP kinase cascade. Broader impacts The project combines genetic, molecular, cellular and genomic approaches to understand the basis of a natural phenomenon, abscission, and to dissect a signaling network in Arabidopsis. This research will serve as an excellent training environment for students and postdoctoral scientists. Training of students and post-doctoral fellows who can use a combination of approaches to study biological processes is critical to advancement in the life sciences. The fourth aim of the project includes outreach to high schools and participation of under-represented groups in research. The PI will collaborate with high school teachers to advance the use of Arabidopsis in the classroom to promote science education and inquiry based learning. Research activities will integrate students from minority serving institutions. Thus, the project will also enhance the infrastructure for research and education by promoting the interaction between scientists, K-12 educators, and students from under-represented groups.