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Apple S ‐ RN ase interacts with an actin‐binding protein, Md MVG , to reduce pollen tube growth by inhibiting its actin‐severing activity at the early stage of self‐pollination induction
Author(s) -
Yang Qing,
Meng Dong,
Gu Zhaoyu,
Li Wei,
Chen Qiuju,
Li Yang,
Yuan Hui,
Yu Jie,
Liu Chunsheng,
Li Tianzhong
Publication year - 2018
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.13929
Subject(s) - actin , rnase p , actin binding protein , biology , pollen tube , microbiology and biotechnology , microfilament , mutant , actin cytoskeleton , cytoskeleton , biochemistry , rna , pollen , gene , botany , pollination , cell
Summary In S ‐ RN ase‐mediated self‐incompatibility, S ‐ RN ase secreted from the style destroys the actin cytoskeleton of the self‐pollen tubes, eventually halting their growth, but the mechanism of this process remains unclear. In vitro biochemical assays revealed that S ‐ RN ase does not bind or sever filamentous actin (F‐actin). In apple ( Malus domestica ), we identified an actin‐binding protein containing myosin, villin and GRAM (Md MVG ), that physically interacts with S‐ RN ase and directly binds and severs F‐actin. Immunofluorescence assays and total internal reflection fluorescence microscopy indicated that S ‐ RN ase inhibits the F‐actin‐severing activity of Md MVG in vitro . In vivo , the addition of S ‐ RN ase to self‐pollen tubes increased the fluorescence intensity of actin microfilaments and reduced the severing frequency of microfilaments and the rate of pollen tube growth in self‐pollination induction in the presence of Md MVG overexpression. By generating 25 single‐, double‐ and triple‐point mutations in the amino acid motif E‐E‐K‐E‐K of Md MVG via mutagenesis and testing the resulting mutants with immunofluorescence, we identified a triple‐point mutant, Md MVG (E167A/E171A/K185A) , that no longer has F‐actin‐severing activity or interacts with any of the four S ‐haplotype S ‐ RN ases, indicating that all three amino acids (E167, E171 and K185) are essential for the severing activity of Md MVG and its interaction with S ‐ RN ases. We conclude that apple S ‐ RN ase interacts with Md MVG to reduce self‐pollen tube growth by inhibiting its F‐actin‐severing activity.