Transporters involved in pH and K+ homeostasis affect pollen wall formation, male fertility, and embryo development.
Flowering plant genomes encode multiple cation/H+ exchangers (CHXs) whose functions are largely unknown. AtCHX17, AtCHX18, and AtCHX19 are membrane transporters that modulate K+ and pH homeostasis and are localized in the dynamic endomembrane system. Loss of function reduced seed set, but the particular phase(s) of reproduction affected was not determined. Pollen tube growth and ovule targeting of chx17chx18chx19 mutant pollen appeared normal, but reciprocal cross experiments indicate a largely male defect. Although triple mutant pollen tubes reach ovules of a wild-type pistil and a synergid cell degenerated, half of those ovules were unfertilized or showed fertilization of the egg or central cell, but not both female gametes. Fertility could be partially compromised by impaired pollen tube and/or sperm function as CHX19 and CHX18 are expressed in the pollen tube and sperm cell, respectively. When fertilization was successful in self-pollinated mutants, early embryo formation was retarded compared with embryos from wild-type ovules receiving mutant pollen. Thus CHX17 and CHX18 proteins may promote embryo development possibly through the endosperm where these genes are expressed. The reticulate pattern of the pollen wall was disorganized in triple mutants, indicating perturbation of wall formation during male gametophyte development. As pH and cation homeostasis mediated by AtCHX17 affect membrane trafficking and cargo delivery, these results suggest that male fertility, sperm function, and embryo development are dependent on proper cargo sorting and secretion that remodel cell walls, plasma membranes, and extracellular factors.
Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
Senthilkumar
S
Padmanaban
Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
Daniel D
DD
Czerny
Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
Kara A
KA
Levin
Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02912, USA.
Alexander R
AR
Leydon
Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
Robert T
RT
Su
Laboratory for Biological Ultrastructure, University of Maryland, College Park, MD 20742, USA.
Timothy K
TK
Maugel
Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003, USA.
Yanjiao
Y
Zou
Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA.|Department of Biotechnology, Burapha University, Chon-Buri 20131, Thailand.
Salil
S
Chanroj
Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003, USA.
Alice Y
AY
Cheung
Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02912, USA.
Mark A
MA
Johnson
Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, MD 20742, USA.|Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD 20742, USA.|Maryland Agricultural Experiment Station, University of Maryland, College Park, MD 20742, USA.
Heven
H
Sze
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D005298:Fertility; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D053205:Pollen Tube / Q000254:growth & development; D011188:Potassium / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism
D029681:Arabidopsis Proteins; C493886:CHX17 protein, Arabidopsis; D017923:Sodium-Hydrogen Exchangers; D011188:Potassium
Cation; endomembrane; male fertility; pollen; proton; transporter; wall formation