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"Molecular mechanisms driving plant cell morphogenesis"

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Thursday 26 October 2017, 11:00 - 12:30


The timing and orientation of cell divisions in plants is of utmost importance for cell shape and morphology due to the cell-wall-imposed fixation of plant cells (Müller et al., 2009; Müller, 2012). During cytokinesis, cell plate formation is initiated in the division plane and its expansion progresses laterally towards the parental wall aided by the cytoskeletal phragmoplast. Intriguingly, the site of cell plate fusion, designated the cortical division zone is already selected at the G2/M transition and delineated at the cell cortex by the preprophase band (PPB). Recently, research in my lab advanced the understanding of this process. Using life cell imaging and fluorescence recovery after photo-bleaching analysis, we revealed the subcellular localization and dynamic behavior of kinesin-12 PHRAGMPOLAST ORIENTING KINESIN (POK) 1 at the cortical division zone throughout mitosis (Lipka et al., 2014). Simultaneous mutation of the functionally redundant POK1 and POK2 pair lead to oblique cell wall insertions due to the mismatch of PPB and phragmoplast position. cortical division zone markers TANGLED and RanGAP1, which both interact with the carboxy (C)-terminal of POK1 are not retained at the cortical division zone in pok1pok2 mutants (Xu et al., 2008; Lipka et al., 2014) suggesting that POKs act as a molecular framework to preserve the cortical division zone. Despite the recent progress, the molecular pathways that enable maintenance of the cortical division zone and its recognition by the approaching phragmoplast are poorly defined.

To gain further insight, we pursue cell biological characterization of POK dependent pathways using the pok1pok2 double mutant as a genetic tool and dissect POK functions by characterizing POK protein domains. Furthermore, we are using reverse genetics combined with life cell imaging to characterize recently identified POK inter-actors PHGAPs, which are recruited to the cortical division zone. Mutant analysis suggest that they act upstream of POK1 in prophase, but their maintenance is POK-dependent (Stöckle et al., 2016). Our findings suggests that Rop GTPase dependent cell polarity signaling and symmetric division plane establishment share similar signaling pathways.

Location Jozef Schell Seminar Room
Contact Dr Sabine Mueller
University of Tübingen
Center for Plant Molecular Biology - ZMBP
Developmental Genetics