Edinburgh, Scotland, United Kingdom - TAIR

Endocytic trafficking: New players in FLS2/
flagellin signaling
Cell surface receptor kinases serve as sensors for internal and external stimuli
that trigger signaling cascades and are evidently important for developmental
regulation and self from non-self discrimination. Active defenses are initiated
upon receptor-mediated perception of so-called pathogen-associated molecular
patterns (PAMPs). One of the best-studied PAMPs is bacterial flagellin (flg22),
which is recognized by the receptor kinase Flagellin Sensing 2 (FLS2). Upon
flg22 sensing, FLS2 elicits an array of defense responses, which enhance plant
immunity to prevent bacterial infection and proliferation. Concomitantly, activated
FLS2 translocates to an endosomal pool reminiscent of receptor-mediated
endocytosis. Although both, PAMP perception and receptor trafficking became
a focus of research in the past years, there is largely nothing known about
downstream molecules of receptor signaling and regulatory components of
receptor endocytosis.
To identify such components we searched for FLS2 Interacting Proteins (FIPs)
by yeast split-ubiquitin screening. FIP1 is a member of a gene family encoding
transmembrane proteins, which potentially regulate cellular Ca2+ levels. Using
chemical interference we showed that flg22-triggered FLS2 endocytosis requires
changes in the Ca2+ distribution. FIP1-GFP was clearly localized to the plasma
membrane and notably, was internalized into endosomes upon flg22 treatment.
We will further discuss in planta interaction and co-localization of FLS2 and FIP1.
Moreover, mutant plants devoid of FIP1 and its close homologue FIP1-like are
impaired in flg22-triggered responses, which was confirmed by chemical
inhibition of FIP1 activity. This suggests that FIP1 is a critical component of
FLS2 signaling. A detailed characterization of fip1/fip1-like phenotypes will be
presented. Unlike FIP1, FIP2 appeared to mostly localize to the cytoplasm. It
codes for a soluble kinase and currently, we are addressing the relevance of
FIP2 in FLS2 signaling and endocytosis.
77
C26
Thursday 15:00 - 15:15
Plant Defence
Nicolas Frei dit Frey
Stephanie Laurent
Denise Altenbach
Silke Robatzek
Max-Planck-Institute for
Plant Breeding Research
Carl-von-Linne-Weg 10
50829 Cologne
Germany