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United States Department of Agriculture

Agricultural Research Service

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Location: Plant Gene Expression Center

2012 Annual Report

1a. Objectives (from AD-416):
1. To identify additional components of the CLAVATA meristem signal transduction pathway. [NP 301, C 4, PS 4A] 2: To characterize the role of microRNAs and their target genes in regulating Arabidopsis shoot meristem activity. [NP 301, C 4, PS 4A] 3: To determine the function of the Arabidopsis BOP1 and BOP2 genes in regulating shoot apical meristem activity and leaf development. [NP 301, C 4, PS 4A] 4: To develop and test hypotheses to determine how knowledge of plant architectural genes in Arabidopsis can be applied to crop plants. [NP 301, C 4, PS 4A]

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.

3. Progress Report:
Progress was made on all four project objectives, which fall under National Program 301, Plant Genetic Resources, Genomics and Genetic Improvement. Progress on this project focuses on addressing Problem 3A – the need for fundamental knowledge of plant biological and molecular processes. Under objective 1, we made progress in identifying additional components of the CLAVATA (CLV) signaling pathway in the model plant Arabidopsis thaliana. Towards this accomplishment, we used genetic and molecular techniques to analyze whether a putative downstream target gene contributes to the fruit patterning defect identified in ult1 kan1 mutant plants. Under objective 2, we made significant progress in characterizing the role of small regulatory microRNAs (miRNAs) and their target genes in regulating shoot stem cell activity. We made progress in characterizing the stem cell defect found in the miRNA pathway mutant JABBA MODIFIER1 (JM1) using genetic and molecular methods. Under objective 3, we made progress in determining the function of the BOP1 and BOP2 genes in leaf development. We progressed in analyzing the expression of two downstream transcription factor genes in the leaves of plants with reduced function of the BOP target genes CLE5 and CLE6. Under objective 4, we progressed in developing and testing hypotheses to determine how knowledge of plant architectural genes in Arabidopsis can be applied to crop plants. Towards accomplishing this we identified in the maize genomic sequence database two loci encoding small proteins that may have similar expression and function characteristics as the Arabidopsis CLE5 and CLE6 signaling molecules.

4. Accomplishments
1. Characterization of CLE signaling gene function in plant embryos. This work addresses the question of what biological processes during plant development are regulated by small signaling molecules. ARS scientists in the Plant Gene Expression Center in Albany, California, reported in the journal The Plant Cell that CLE8, a member of the CLV3-related CLE family of small signaling molecules, controls key intercellular signaling events during Arabidopsis embryo formation in developing seeds. CLE8 gene is specifically expressed in young embryos and the surrounding nutrient endosperm and acts in a signaling module that controls cell patterning and cell division in embryos and endosperm. The results demonstrate that CLE8 functions to promote seed growth and overall seed size. This accomplishment will facilitate the identification of related genes in crop plants that have similar expression patterns and functions, benefiting agriculture by identifying genes that control key traits in embryos which can be manipulated to potentially improve seed yield and/or increase germination efficiency.

Review Publications
Jun, J.H., Fiume, E., Roeder, A.H., Meng, L., Sharma, V.K., Osmont, K.S., Baker, C., Ha, C.M., Meyerowitz, E.M., Feldman, L.J., Fletcher, J.C. 2010. Comprehensive analysis of CLE polypeptide signaling gene expression and over-expression activity in Arabidopsis. Plant Physiology. 154:1721-1736.

Last Modified: 06/28/2017
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