Signal Transduction and the Regulation of Organ Abscission in Arabidopsis

植物的脱落是一种普遍公认的自然现象。它是一个发育过程的产物，这个过程被编程为从植物体内主动脱落器官。最近的研究结果支持了从假定的配体到受体再到下游效应子的信号通路在拟南芥中控制转录的作用。花序脱落缺陷（IDA）表达的改变，其编码预测的分泌小蛋白，受体样蛋白激酶HAESA（HAE）和HAESA样2（HSL 2）、促分裂原活化蛋白激酶激酶4（MKK 4）和MKK 5的基因都显示出类似的功能丧失型脱落缺陷表型。相反，组成型活性MKKs的表达挽救了hae hs 12和ida的表达缺陷表型。此外，MAP激酶活性在经历分裂的花的区域中降低。对在hae hsl 2背景下过表达IDA的植物的分析表明，HAE和HSL 2对IDA是上位性的。总之，这些结果表明IDA、HAE、HSL 2和MAP激酶级联功能在共同的途径中调节解离。该研究的目的是检验IDA、HAE、HSL 2和MAP激酶级联之间存在直接顺序相互作用以调节释放区中细胞的分离的假设。第一个目的是确定IDA是否与植物中的HAE和HSL 2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激酶以确定它们是否在解离信号级联中起作用。第三个目的是研究在细胞分离之前触发的细胞变化，以开始理解IDA-HAE-MAP激酶级联靶向的过程。更广泛的影响该项目结合遗传，分子，细胞和基因组的方法来了解自然现象的基础，拟南芥，并剖析信号网络。这项研究将为学生和博士后科学家提供良好的培训环境。培养学生和博士后研究员，使他们能够综合使用各种方法研究生物过程，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，并让代表性不足的群体参与研究。PI将与高中教师合作，促进拟南芥在课堂上的使用，以促进科学教育和基于探究的学习。研究活动将使少数民族服务机构的学生融入其中。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.