Arabidopsis FIM5 decorates apical actin filaments and regulates their organization in the pollen tube.
The actin cytoskeleton is increasingly recognized as a major regulator of pollen tube growth. Actin filaments have distinct distribution patterns and dynamic properties within different regions of the pollen tube. Apical actin filaments are highly dynamic and crucial for pollen tube growth. However, how apical actin filaments are generated and properly constructed remains an open question. Here we showed that Arabidopsis fimbrin5 (FIM5) decorates filamentous structures throughout the entire tube but is apically concentrated. Apical actin structures are disorganized to different degrees in the pollen tubes of fim5 loss-of-function mutants. Further observations suggest that apical actin structures are not constructed properly because apical actin filaments cannot be maintained at the cortex of fim5 pollen tubes. Actin filaments appeared to be more curved in fim5 pollen tubes and this was confirmed by measurements showing that the convolutedness and the rate of change of convolutedness of actin filaments was significantly increased in fim5 pollen tubes. This suggests that the rigidity of the actin filaments may be compromised in fim5 pollen tubes. Further, the apical cell wall composition is altered, implying that tip-directed vesicle trafficking events are impaired in fim5 pollen tubes. Thus, we found that FIM5 decorates apical actin filaments and regulates their organization in order to drive polarized pollen tube growth.
Key Laboratory of Plant Molecular Physiology, Institute of Botany Chinese Academy of Sciences, Beijing 100093 China University of Chinese Academy of Sciences, Beijing 100049 China.
Meng
M
Zhang
Key Laboratory of Plant Molecular Physiology, Institute of Botany Chinese Academy of Sciences, Beijing 100093 China University of Chinese Academy of Sciences, Beijing 100049 China.
Ruihui
R
Zhang
Center for Plant Biology, School of Life Sciences, Tsinghua University Beijing 100084, China Tsinghua-Peking Joint Center for Life Sciences, Beijing 100084 China.
Xiaolu
X
Qu
Key Laboratory of Plant Molecular Physiology, Institute of Botany Chinese Academy of Sciences, Beijing 100093 China Center for Plant Biology, School of Life Sciences, Tsinghua University Beijing 100084, China National Center for Plant Gene Research, Beijing 100101 China sjhuang@ibcas.ac.cn.
Shanjin
0000-0001-9517-2515
S
Huang
D008841:Actin Cytoskeleton / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism; D053205:Pollen Tube / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
D029681:Arabidopsis Proteins; C000625597:FIM5 protein, Arabidopsis; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins
Actin-binding protein; Arabidopsis thaliana; actin bundles; actin dynamics; fimbrin; pollen tube.