Signal Transduction and the Regulation of Organ Abscission in Arabidopsis

植物的脱落是一种公认的自然现象。它是一个发育过程的产物，这个过程被设定为主动从植物体内脱落器官。最近的研究结果支持了拟南芥中从配体到受体再到下游效应物的信号通路在控制脱落中的作用。编码预测分泌小蛋白的脱落花序缺陷基因（IDA）、受体样蛋白激酶HAESA （HAE）和HAESA样2 （HSL2）、丝裂原活化蛋白激酶激酶4 （MKK4）和MKK5的基因表达的改变都显示出类似的脱落功能缺失表型。相反，组成型活性MKKs的表达挽救了hsl2和ida的脱落缺陷表型。此外，MAP激酶活性在花发生脱落的区域降低。对具有hsl2背景的IDA过表达植物的分析表明，hae和hsl2对IDA具有上位性。综上所述，这些结果表明IDA、HAE、HSL2和MAP激酶级联在调节脱落的共同途径中起作用。本研究的目的是验证IDA、HAE、HSL2和MAP激酶级联之间存在直接顺序相互作用以调节脱落区细胞分离的假设。第一个目的是确定IDA是否与植物HAE和HSL2受体结合并激活这些受体。第二个目的是测试候选MAP激酶和MAP激酶激酶，以确定它们是否在脱落信号级联中起作用。第三个目的是研究细胞分离前触发的细胞变化，以开始了解IDA-HAE-MAP激酶级联的靶过程。该项目结合了遗传、分子、细胞和基因组的方法来理解自然现象——脱落的基础，并剖析拟南芥的信号网络。本研究将为学生和博士后提供良好的培养环境。培养能够使用多种方法研究生物过程的学生和博士后对生命科学的进步至关重要。该项目的第四个目标包括向高中推广和让代表性不足的群体参与研究。该项目将与高中教师合作，在课堂上推广拟南芥的使用，以促进科学教育和基于探究的学习。研究活动将整合来自少数民族服务机构的学生。因此，该项目还将通过促进科学家、K-12教育工作者和来自代表性不足群体的学生之间的互动，加强研究和教育的基础设施。

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.