The Developmental Role of Lateral Organ Boundaries and Related Genes

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0318822SpringerLeaves and other lateral organs initiate from the flanks of the shoot apical meristem (SAM), and forming lateral organs develop axes of asymmetry in response to positional cues from the SAM. The LATERAL ORGAN BOUNDARIES (LOB) gene is expressed in a band of cells between the SAM and initiating lateral organs. LOB expression is regulated both by genes that are important for SAM formation, and genes that are important for leaf development, suggesting that LOB may be involved in signaling between the SAM and organ primordia. LOB encodes a novel protein that is unique to plants and defines the conserved LOB domain. Forty-three Arabidopsis genes encode proteins that contain a LOB domain. Among these, ASYMMETRIC LEAVES2 (AS2), LBD10, LBD25, and LBD36 are most closely related to LOB. Of the LOB-domain genes thus far analyzed, only AS2 results in a visible phenotype when mutated. These observations suggest that the members of the LOB-domain gene family exhibit functional redundancy. Ectopic expression of AS2 results in the formation of lateral organs that have abnormal abaxial-adaxial polarity, implicating AS2, and perhaps closely related genes, in the establishment adaxial cell fates. This research focuses on understanding the developmental role of LOB and related genes. LOB and closely related genes will be characterized by genetic analyses. Plants that carry single or multiple mutant combinations will be identified to uncover the developmental roles each gene plays. The role of AS2 in polarity determination will be investigated. LOB cis-acting regulatory sequences will be characterized. Proteins that interact with LOB will be identified. The long-term goals of this research are to understand the mechanisms of lateral organ formation from the shoot apical meristem, and in particular what role LOB-domain genes play in this process. The project will provide training for undergraduate and graduate students and a postdoctoral associate in a high minority-enrollment institution.