The role of the transcription factor JAGGED in early floral organogenesis

Initiation of organ primordia from pools of undifferentiated cells requires coordinated cytoplasmic growth, oriented cell wall extension, and cell cycle progression. It is debated which of these processes are primary drivers for organ morphogenesis and directly targeted by developmental regulators. The single zinc finger transcription factor JAGGED (JAG) is a direct target of several floral organ identity genes and is expressed in early organ primordia (Dinneny et al., 2004; Ohno et al., 2004; Gomez et al., 2005; Kaufmann et al., 2009). Loss of function jag mutants have narrow floral organs with reduced distal growth. Quantitative 3D imaging has revealed that JAG is required for the transition from meristematic to organ primordium cell behaviour. The transition involves an increase in the rates of cell division and cell growth, a shift from isotropic to anisotropic growth, and modifications in cell size homeostasis in primordia (Schiessl et al., 2012). In this project, ChIP-Seq was combined with transcriptome analysis to identify global direct target genes of JAG. Consistent with the roles of JAG during organ initiation and organ growth, I found that JAG directly repressed genes involved in meristem development, such as the TALE PROTEIN BELL1 and genes involved in organ boundaries specification such as PETAL LOSS. In addition, JAG directly regulated genes involved in growth regulatory pathways, tissue polarity, cell wall modification, and cell cycle progression. For example, JAG directly repressed the cell cycle inhibitors KIP RELATED PROTEIN 2 and 4 (KRP2/4). The krp2 and krp4 mutations suppressed jag loss of function defects in organ growth and cell type patterning. In particular, loss of KRP4 rescued the defects of cell size homeostasis in the primordia of the jag loss of function mutant. In summary, this work revealed that JAG directly coordinates organ patterning with cellular processes required for tissue growth.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2014

Author dc:creator

• Schiessl, Katharina

Language dc:language

en