2007 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). BSL 1; 7/1/05.
The first objective of our CRIS project is to identify additional components of the CLAVATA (CLV) signal transduction pathway. To accomplish this we screened 45 EMS-mutagenized clv3-3 families for modifier phenotypes, for a total of 3600 M2 progeny analyzed. Unfortunately, we did not recover any modifier alleles within this population, and only a few alleles of previously identified developmental genes. We have discontinued screening this population because it was clearly an ineffective mutagenesis. Instead, we will focus on identifying enhancer and suppressor mutants of ult1-2, which also affects Arabidopsis stem cell accumulation through a pathway that overlaps with that of clv3.
The second objective of our CRIS project is to characterize the role of microRNAs and their target genes in regulating shoot apical meristem activity. To accomplish this we are in the process of determining which HD-ZIP genes contribute to the jba-1D shoot meristem phenotype. The constructs containing the HD-ZIP genes have been made and are currently being transformed into jba-1D plants in preparation for phenotypic analysis.
The third objective of our CRIS project is to determine the function of the BOP1 and BOP2 genes in regulating shoot apical meristem activity and leaf development. To accomplish this we are in the process of determining whether genes required to control leaf polarity, leaf cell fate specification, or leaf cell signaling are direct targets of BOP1.
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. Our milestone for FY2007 was to annotate the ULT1 gene ortholog on the rice genome and determine the chromosomal location of the OsULT1 gene. This was done for us by the public rice gene annotation project, which identified the ULT1 gene ortholog on chromosome 1 as locus Os01g0780800.
BOP1 and BOP2 Regulatory Targets.
Previous work has revealed that the BOP1 and BOP2 plant developmental regulatory proteins act early in a molecular pathway that regulates Arabidopsis leaf formation, but the specific components of this pathway are not fully known. Our accomplished goal was to identify new downstream target genes of BOP1 and BOP2. PGEC, Albany, CA scientists used molecular experiments to show that BOP1 and BOP2 control the expression of genes that regulate leaf cell fate, as well as two genes encoding putative signaling molecules that are closely related to the key stem cell regulator CLV3. Results demonstrate a critical role for the BOP genes in a critical developmental regulatory pathway that affects leaf differentiation. Manipulation of such a pathway in crops 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.
Translate ULT1 Sequences to Maize.
This work addresses the problem of applying the knowledge of plant architectural genes in Arabidopsis to crop plants. Scientists in the PGEC, Albany, CA provided clones and sequences corresponding to the Arabidopsis ULT1 gene to determine its expression pattern in maize tissues and sequence the maize ULT1 gene from their population of uncloned meristem mutants. Manipulation of the ULT1 stem cell regulatory pathway in crops 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.
5.Significant Activities that Support Special Target Populations
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Roxrud, I., Lid, S., Fletcher, J.C., Opsahl-Sorteberg, H.-G., Schmidt, E. 2007. GASA4, One of the 14-Member Arabidopsis GASA Family of Small Polypeptides, Regulates Flowering and Seed Development. Plant And Cell Physiology. 48(3):471-483.
Ha, C., Jun, J., Nam, H., Fletcher, J.C. 2007. BLADE-ON-PETIOLE1 and 2 Control Arabidopsis Lateral Organ Fate through Regulation of LOB Domain and Adaxial-Abaxial Polarity Fenes. The Plant Cell. 19:1809-1825.