CCS52A2/FZR1, a cell cycle regulator, is an essential factor for shoot apical meristem maintenance in <it>Arabidopsis thaliana</it>

<p>Abstract</p> <p>Background</p> <p>Cell division and cell fate decisions regulate organ formation and function in plant growth and development. It is still unclear how specific meristematic regulatory networks operate with the cell cycle machinery to translate stem cell identity and maintenance into cellular behavior. In this study, we address these questions by analysis of a shoot apex defective mutant, namely <it>xcm9.</it></p> <p>Results</p> <p>Phenotypic analysis of the <it>xcm9</it> mutant reveals concomitant premature termination of floral shoots with frequent bifurcation of the shoot apices, stems, and flowers. Microscopic observations show irregular cell organization in shoot apical meristems of <it>xcm9</it>. Positional cloning revealed that <it>xcm9</it> is a loss of function allele of the <it>CCS52A2/FZR1</it> gene, which has previously been implicated in root development. Expression analysis demonstrated that <it>CCS52A2</it> maintains a higher transcriptional expression level in actively dividing tissue. Genetic studies indicated that the <it>CCS52A</it>2 gene functions together with <it>WUSCHEL</it> (<it>WUS</it>) and <it>CLAVATA3</it> (<it>CLV3</it>) in regulating the development of the shoot meristem, and also contributes to this regulation together with the chromatin remodeling pathway. In addition, fewer <it>xcm9</it> cells express <it>CYCLIN B1:1</it>, showing that cell cycle progression is disrupted in the mutant.</p> <p>Conclusion</p> <p>We propose that the <it>CCS52A2</it> gene is a mediator that functions together with meristematic genes to regulate meristem organization, and cross-functions with chromatin regulators in cell cycle progression during shoot apical meristem development.</p>