2 research outputs found
The SERK1 receptor-like kinase regulates organ separation in Arabidopsis flowers
Through a sensitized screen for novel components of pathways regulating organ separation in Arabidopsis flowers, we have found that the leucine-rich repeat receptor-like kinase SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE1 (SERK1) acts as a negative regulator of abscission. Mutations in SERK1 dominantly rescue abscission in flowers without functional NEVERSHED (NEV), an ADP-ribosylation factor GTPase-activating protein required for floral organ shedding. We previously reported that the organization of the Golgi apparatus and location of the trans-Golgi network (TGN) are altered in nev mutant flowers. Disruption of SERK1 restores Golgi structure and the close association of the TGN in nev flowers, suggesting that defects in these organelles may be responsible for the block in abscission. We have also found that the abscission zones of nev serk1 flowers are enlarged compared to wild-type. A similar phenotype was previously observed in plants constitutively expressing a putative ligand required for organ separation, INFLORESCENCE DEFICIENT IN ABSCISSION (IDA), suggesting that signaling through IDA and its proposed receptors, HAESA and HAESA-LIKE2, may be deregulated in nev serk1 abscission zone cells. Our studies indicate that in addition to its previously characterized roles in stamen development and brassinosteroid perception, SERK1 plays a unique role in modulating the loss of cell adhesion that occurs during organ abscission
Regulation of membrane trafficking and organ separation by the NEVERSHED ARF-GAP protein
Cell separation, or abscission, is a highly specialized process in plants
that facilitates remodeling of their architecture and reproductive success.
Because few genes are known to be essential for organ abscission, we conducted
a screen for mutations that alter floral organ shedding in
Arabidopsis. Nine recessive mutations that block shedding were found
to disrupt the function of an ADP-ribosylation factor-GTPase-activating
protein (ARF-GAP) we have named NEVERSHED (NEV). As predicted by its homology
to the yeast Age2 ARF-GAP and transcriptional profile, NEV influences other
aspects of plant development, including fruit growth. Co-localization
experiments carried out with NEV-specific antiserum and a set of plant
endomembrane markers revealed that NEV localizes to the trans-Golgi
network and endosomes in Arabidopsis root epidermal cells.
Interestingly, transmission electron micrographs of abscission zone regions
from wild-type and nev flowers reveal defects in the structure of the
Golgi apparatus and extensive accumulation of vesicles adjacent to the cell
walls. Our results suggest that NEV ARF-GAP activity at the trans-Golgi
network and distinct endosomal compartments is required for the proper
trafficking of cargo molecules required for cell separation