2008 Annual Report
1a.Objectives (from AD-416)
Objective 1: To identify additional components of the CLAVATA meristem signal transduction pathway.
Objective 2: To characterize the role of microRNAs and their target genes in regulating Arabidopsis shoot apical meristem activity.
Objective 3: To determine the function of the Arabidopsis BOP1 and BOP2 genes in regulating shoot apical meristem activity and leaf development.
Objective 4: To develop and test hypotheses to determine how knowledge of plant architectural genes in Arabidopsis can be applied to crop plants.
1b.Approach (from AD-416)
Identify, isolate and characterize genes that regulate plant architecture in model systems and agriculturally important crops by.
1)using a sensitized genetic screen to uncover novel components of the Arabidopsis thaliana CLAVATA stem cell signaling pathway;.
2)determining the role of a small regulatory RNA and its five target genes in regulating stem cell maintenance during development;.
3)analyzing the function of the BOP1 and BOP2 genes in regulating stem cell activity and leaf formation; and.
4)developing and testing hypotheses on how knowledge of plant architectural genes in Arabidopsis can be applied to crop plants through the identification and functional analysis of orthologous genes. REPLACES 5335-21000-016-00D (4/06).
The first objective of our CRIS project is to identify additional components of the CLAVATA (CLV) signaling pathway. To accomplish this we screened mutagenized clv3 families for modifier phenotypes, but we discontinued screening this population because it was an ineffective mutagenesis. Instead, we are focusing on identifying enhancers and suppressors of a mutation in ULTRAPETALA1 (ULT1), which affects Arabidopsis stem cell accumulation through a pathway overlapping that of CLV3. We have identified two independent enhancers and one suppressor of the ult1 stem cell phenotype, and have completed backcrosses and performed complementation tests with all three lines.
The second objective of our CRIS project is to characterize the role of microRNAs (miRNAs) and their target genes in regulating shoot apical meristem activity. To accomplish this we are have used genetic and molecular techniques to determine which of the five HD-ZIP target genes contribute to the jabba-1D shoot meristem phenotype caused by up-regulation of the miR166g gene. The expression patterns of several of the seven miR166 genes have been recently reported in the literature, and we are in the process of analyzing the expression patterns of the remaining family members.
The third objective of our CRIS project is to determine the function of the BLADE-ON-PETIOLE1 (BOP1) and BOP2 genes in regulating shoot apical meristem activity and leaf formation. To accomplish this we have analyzed the expression patterns of the BOP1 and BOP2 genes throughout wild-type Arabidopsis development, and also in the background of several mutants with reduced shoot apical meristem function. We have also shown that BOP1 acts as a transcriptional activator protein and are in the process of demonstrating direct interaction between BOP1 protein and a key target gene locus.
The fourth objective of our CRIS project is to develop and test hypotheses to determine how knowledge of plant architectural genes in Arabidopsis can be applied to crop plants. To accomplish this we have provided BOP1 and BOP2 clones and sequences to maize researchers, and have identified a putative maize BOP2 insertion line. BOP1 and BOP2 gene orthologs have also been annotated on the rice genome sequence by the public rice gene annotation project.
These relate to NP302, Component 1.
Characterization of EMB1611 Shoot Meristem Regulatory Gene: This work addresses the identification of genetic pathways that control Arabidopsis plant architecture that can be translated to crop species. ARS scientists in the Plant Gene Expression Center in Albany, CA identified a role for the essential gene EMB1611 in shoot stem cell function during development through its maintenance of the CLV stem cell regulatory pathway. We also demonstrated that EMB1611 functions in young plant tissues to sustain the cells in an actively dividing state. Manipulation of pathways such as this in crop plants may lead to increased yields, benefiting domestic farmers as well as export markets. This accomplishment addresses National Program NP302 Component 1, problem statement 1A – Advancing From Model Plants to Crop Plants.
Analysis of ULT1 Regulatory Mechanism: This work addresses the question of how the key stem cell regulatory gene ULT1 functions in Arabidopsis for future application to crop plants. ARS scientists in the Plant Gene Expression Center in Albany, CA determined that ULT1 acts genetically as a trithorax Group factor, part of a chromatin remodeling complex that maintains target gene expression in an active state. We also showed that ULT1 maintains an active chromatin state at a target gene locus that is critical for regulating stem cell accumulation for fruit formation. Understanding the mechanism of the ULT1 activity in stem cell regulation may lead to novel ways to control plant architecture in crop plants, and also sheds light on the activities of ULT1-related proteins that play important roles in human disease. This accomplishment addresses National Program NP302 Component 1, problem statement 1A – Advancing From Model Plants to Crop Plants.
5.Significant Activities that Support Special Target Populations
|Number of Non-Peer Reviewed Presentations and Proceedings||4|
Jun, J., Fiume, E., Fletcher, J.C. 2007. The CLE family of plant polypeptide signaling molecules. Cellular and Molecular Life Sciences. 64(11):1420-9071 (Online)