PCP-B class pollen coat proteins are key regulators of the hydration checkpoint in Arabidopsis thaliana pollen-stigma interactions.
The establishment of pollen-pistil compatibility is strictly regulated by factors derived from both male and female reproductive structures. Highly diverse small cysteine-rich proteins (CRPs) have been found to play multiple roles in plant reproduction, including the earliest stages of the pollen-stigma interaction. Secreted CRPs found in the pollen coat of members of the Brassicaceae, the pollen coat proteins (PCPs), are emerging as important signalling molecules that regulate the pollen-stigma interaction. Using a combination of protein characterization, expression and phylogenetic analyses we identified a novel class of Arabidopsis thaliana pollen-borne CRPs, the PCP-Bs (for pollen coat protein B-class) that are related to embryo surrounding factor (ESF1) developmental regulators. Single and multiple PCP-B mutant lines were utilized in bioassays to assess effects on pollen hydration, adhesion and pollen tube growth. Our results revealed that pollen hydration is severely impaired when multiple PCP-Bs are lost from the pollen coat. The hydration defect also resulted in reduced pollen adhesion and delayed pollen tube growth in all mutants studied. These results demonstrate that AtPCP-Bs are key regulators of the hydration 'checkpoint' in establishment of pollen-stigma compatibility. In addition, we propose that interspecies diversity of PCP-Bs may contribute to reproductive barriers in the Brassicaceae.
Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
Ludi
L
Wang
Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
Lisa A
LA
Clarke
Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
Russell J
RJ
Eason
Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
Christopher C
CC
Parker
Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
Baoxiu
B
Qi
Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
Rod J
RJ
Scott
Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
James
J
Doughty
D000268:Adhesiveness; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D019143:Evolution, Molecular; D035264:Flowers / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D009154:Mutation / Q000235:genetics; D010802:Phylogeny; D011058:Pollen / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D053205:Pollen Tube / Q000254:growth & development / Q000648:ultrastructure; D011110:Polymorphism, Genetic; D017386:Sequence Homology, Amino Acid; D014867:Water / Q000378:metabolism*
D029681:Arabidopsis Proteins; D014867:Water; D003545:Cysteine

Arabidopsis thaliana
; compatibility; pollen coat proteins; pollen hydration; pollen-stigma interaction; reproduction; signalling