Baoxiu Qi

A Golgi and tonoplast localized S-acyl transferase is involved in cell expansion, cell division, vascular patterning and fertility in Arabidopsis.

S-acylation of eukaryotic proteins is the reversible attachment of palmitic or stearic acid to cysteine residues, catalysed by protein S-acyl transferases that share an Asp-His-His-Cys (DHHC) motif. Previous evidence suggests that in Arabidopsis S-acylation is involved in the control of cell size, polarity and the growth of pollen tubes and root hairs. Using a combination of yeast genetics, biochemistry, cell biology and loss of function genetics the roles of a member of the protein S-acyl transferase PAT family, AtPAT10 (At3g51390), have been explored. In keeping with its role as a PAT, AtPAT10 auto-S-acylates, and partially complements the yeast akr1 PAT mutant, and this requires Cys192 of the DHHC motif. In Arabidopsis AtPAT10 is localized in the Golgi stack, trans-Golgi network/early endosome and tonoplast. Loss-of-function mutants have a pleiotropic phenotype involving cell expansion and division, vascular patterning, and fertility that is rescued by wild-type AtPAT10 but not by catalytically inactive AtPAT10C192A. This supports the hypothesis that AtPAT10 is functionally independent of the other Arabidopsis PATs. Our findings demonstrate a growing importance of protein S-acylation in plants, and reveal a Golgi and tonoplast located S-acylation mechanism that affects a range of events during growth and development in Arabidopsis.

PCP-B class pollen coat proteins are key regulators of the hydration checkpoint in Arabidopsis thaliana pollen–stigma interactions

Summary 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 At PCP‐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.