THE ROLE OF FLOWERING LOCUS D (FD) AND HISTONE DEACETYLASE 19 (HDA19) IN STEM CELL MAINTENANCE IN ARABIDOPSIS THALIANA

Shoot apical meristems (SAMs) remain active throughout reproductive development in wild-type Arabidopsis plants. The SAM exists as a small amount of undifferentiated cells located in the center of the apex of the floral stem. Transcription factors play an important regulatory role in stem cell maintenance and floral organ differentiation in the SAM. This study implicates FLOWERING LOCUS D (FD) and HISTONE DEACETYLASE19 (HDA19) as key transcription factors involved in the regulation of stem cell activity. Double mutations in FD and HDA19 genes prevent the process of stem cell self-renewal in the SAM in the reproductive stage of Arabidopsis life cycle. Stem cell proliferation is halted in mutant plants after the initiation of an abnormal cluster of floral organs. This defect is time sensitive as stem cell populations in mutant plants self-renew throughout the vegetative stage and cease proliferation midway through the reproductive stage. RNA in situ hybridization confirms that this cessation in stem cell proliferation in the reproductive stage is due to the misexpression of B Class and C Class floral organ identity genes PISTILLATA (PI), APETALA3 (AP3) and AGAMOUS (AG).