Binding of SEC11 indicates its role in SNARE recycling after vesicle fusion and identifies two pathways for vesicular traffic to the plasma membrane.
SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins drive vesicle fusion in all eukaryotes and contribute to homeostasis, pathogen defense, cell expansion, and growth in plants. Two homologous SNAREs, SYP121 (=SYR1/PEN1) and SYP122, dominate secretory traffic to the Arabidopsis thaliana plasma membrane. Although these proteins overlap functionally, differences between SYP121 and SYP122 have surfaced, suggesting that they mark two discrete pathways for vesicular traffic. The SNAREs share primary cognate partners, which has made separating their respective control mechanisms difficult. Here, we show that the regulatory protein SEC11 (=KEULE) binds selectively with SYP121 to affect secretory traffic mediated by this SNARE. SEC11 rescued traffic block by dominant-negative (inhibitory) fragments of both SNAREs, but only in plants expressing the native SYP121. Traffic and its rescue were sensitive to mutations affecting SEC11 interaction with the N terminus of SYP121. Furthermore, the domain of SEC11 that bound the SYP121 N terminus was itself able to block secretory traffic in the wild type and syp122 but not in syp121 mutant Arabidopsis. Thus, SEC11 binds and selectively regulates secretory traffic mediated by SYP121 and is important for recycling of the SNARE and its cognate partners.
Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Rucha
R
Karnik
Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Ben
B
Zhang
Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Sakharam
S
Waghmare
Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Christin
C
Aderhold
ZMBP Developmental Genetics, D72076 Tübingen, Germany.
Christopher
C
Grefen
Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom michael.blatt@glasgow.ac.uk.
Michael R
MR
Blatt
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002462:Cell Membrane / Q000378:metabolism*; D049109:Cell Proliferation; D048429:Cell Size; D003600:Cytosol / Q000378:metabolism; D005816:Genetic Complementation Test; D056626:Inflorescence / Q000254:growth & development; D008561:Membrane Fusion; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D019441:Plant Epidermis / Q000166:cytology; D011485:Protein Binding; D050765:Qa-SNARE Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D022142:Secretory Vesicles / Q000378:metabolism*
C426230:AT1G12360 protein, Arabidopsis; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C479425:PEN1 protein, Arabidopsis; D010455:Peptides; D050765:Qa-SNARE Proteins; C000606164:SYP122 protein, Arabidopsis