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Schlagwörter:
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Zusammenfassung:
Like pathogens, beneficial endophytic fungi secrete effector proteins to
promote plant colonization, for example, through perturbation of host
immunity. The genome of the root endophyte Serendipita indica encodes a
novel family of highly similar, small alanine- and histidine-rich
proteins, whose functions remain unknown. Members of this protein family
carry an N-terminal signal peptide and a conserved C-terminal DELD
motif.
Here we report on the functional characterization of the
plant-responsive DELD family protein Dld1 using a combination of
structural, biochemical, biophysical and cytological analyses.
The crystal structure of Dld1 shows an unusual, monomeric histidine
zipper consisting of two antiparallel coiled-coil helices. Similar to
other histidine-rich proteins, Dld1 displays varying affinity to
different transition metal ions and undergoes metal ion- and
pH-dependent unfolding. Transient expression of mCherry-tagged Dld1 in
barley leaf and root tissue suggests that Dld1 localizes to the plant
cell wall and accumulates at cell wall appositions during fungal
penetration. Moreover, recombinant Dld1 enhances barley root
colonization by S. indica, and inhibits H2O2-mediated radical
polymerization of 3,3 '-diaminobenzidine.
Our data suggest that Dld1 has the potential to enhance micronutrient
accessibility for the fungus and to interfere with oxidative stress and
reactive oxygen species homeostasis to facilitate host colonization.
