The Role of PENNYWISE and POUND-FOOLISH in the Maintenance of the Shoot Apical Meristem in Arabidopsis

• Published in: Plant physiology (Bethesda) Vol. 156; no. 2; pp. 605 - 614
• Main Authors: Ung, Nolan, Lal, Shruti, Smith, Harley M.S.
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.06.2011
• Subjects: Arabidopsis - cytology; Arabidopsis - genetics; Arabidopsis - physiology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Biological and medical sciences; Body Patterning - genetics; DEVELOPMENT AND HORMONE ACTION; Flowers; Flowers - cytology; Flowers - genetics; Fundamental and applied biological sciences. Psychology; Gene expression regulation; Gene Expression Regulation, Plant; Genes; Genes, Plant - genetics; Homeobox genes; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Inflorescences; Meristem - cytology; Meristem - genetics; Meristem - physiology; Meristems; Mutation - genetics; Plant cells; Plant physiology and development; Plants; Repressor Proteins - metabolism; Reproduction - genetics; Shoot meristems; Stem cells; Transcription, Genetic; Up-Regulation - genetics; Arabidopsis thaliana; Plant physiology; Cruciferae; Dicotyledones; Angiospermae; Spermatophyta; Experimental plant; Apex; Shoot; Meristem
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.110.171462

Growth of the aerial part of the plant is dependent upon the maintenance of the shoot apical meristem (SAM). A balance between the self-renewing stem cells in the central zone (CZ) and organogenesis in the peripheral zone (PZ) is essential for the integrity, function, and maintenance of the SAM. Understanding how the SAM maintains a balance between stem cell perpetuation and organogenesis is a central question in plant biology. Two related BELLl-like homeodomain proteins, PENNYWISE (PNY) and POUND-FOOLISH (PNF), act to specify floral meristems during reproductive development. However, genetic studies also show that PNY and PNF regulate the maintenance of the SAM. To understand the role of PNY and PNF in meristem maintenance, the expression patterns for genes that specifically localize to the peripheral and central regions of the SAM were examined in Arabidopsis (Ambidopsis thaliana). Results from these experiments indicate that the integrity of the CZ is impaired in pny pnf plants, which alters the balance of stem cell renewal and organogenesis. As a result, pools of CZ cells may be allocated into initiating leaf primordia. Consistent with these results, the integrity of the central region of pny pnf SAMs can be partially restored by increasing the size of the CZ. Interestingly, flower specification is also reestablished by augmenting the size of the SAM in pny pnf plants. Taken together, we propose that PNY and PNF act to restrict organogenesis to the PZ by maintaining a boundary between the CZ and PZ.