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Title: The Essential Gene EMB1611 Maintains Shoot Apical Meristem Function During Arabidopsis Development

Author
item LEASURE, COLIN - University Of California
item FIUME, ELISA - University Of California
item Fletcher, Jennifer

Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2009
Publication Date: 2/1/2009
Citation: Leasure, C.D., Fiume, E., Fletcher, J.C. 2009. The Essential Gene EMB1611 Maintains Shoot Apical Meristem Function During Arabidopsis Development. Plant Journal. 57(4):579-92. Epub 2008 Nov 11.

Interpretive Summary: This article reports the expression pattern and molecular functions of an essential gene that is required for sustaining proper shoot growth during Arabidopsis development. We show that the EMB1611 gene encodes a probable membrane-bound protein that is expressed in proliferating cells from early in embryogenesis throughout the plant life cycle. We demonstrate that EMB1611 is required for a number of developmental processes, including shoot and root growth promotion, correctly organizing the cells in the shoot apex, sustaining the shoot stem cell reservoir, and limiting trichome branching. Our findings show that EMB1611 plays a role in maintaining many Arabidopsis cell types in a proliferative, dividing state.

Technical Abstract: The Arabidopsis thaliana genome contains hundreds of genes essential for seed development. Because null mutations in these genes cause embryo lethality, their specific molecular and developmental functions are largely unknown. Here, we identify a role for EMB1611/MEE22, an essential gene in Arabidopsis, in shoot apical meristem maintenance. EMB1611 encodes a large, novel protein with N-terminal coiled-coil regions and two putative transmembrane domains. We show that the partial loss-of-function emb1611-2 mutation causes a range of pleiotropic developmental phenotypes, most dramatically a progressive loss of shoot apical meristem function that causes premature meristem termination. emb1611-2 plants display disorganization of the shoot meristem cell layers early in development, and an associated stem cell fate change to an organogenic identity. Genetic and molecular analysis indicates that EMB1611 is required for maintenance of the CLV-WUS stem cell regulatory pathway in the shoot meristem, but also has WUS-independent activity. In addition, emb1611-2 plants have reduced shoot and root growth, and their rosette leaves form trichomes with extra branches, a defect we associate with an increase in endoreduplication. Our data indicate that EMB1611 functions to maintain cells, particularly those in the shoot meristem, roots and developing rosette leaves, in a proliferative or uncommitted state.