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Homogeneous gold catalysis has experienced extraordinary development since the dawn of this millennium. Oxidative gold catalysis is a vibrant and fertile subfield and has over the years delivered a diverse array of versatile synthetic methods of exceptional value to synthetic practices. This review aims to cover this topic in a comprehensive manner. The discussions are organized by the mechanistic aspects of the metal oxidation states and further by the types of oxidants or oxidizing functional groups. Synthetic applications of oxidative gold catalysis are also discussed. CONTENTS 4.5. Oxidation of Sulfides and Other Functional Groups 9029 5. Conclusion and Outlook 9030 Author Information 9030 Corresponding Author 9030 Authors 9030 Author Contributions 9030 Notes 9030 Biographies 9030 Acknowledgments 9031 References 9031

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Aspartic proteases are a class of proteolytic enzymes with conserved aspartate residues, which are implicated in protein processing, maturation, and degradation. Compared with yeast and animals, plants possess a larger aspartic protease family. However, little is known about most of these enzymes. Here, we characterized two Arabidopsis (Arabidopsis thaliana) putative glycosylphosphatidylinositol (GPI)-anchored aspartic protease genes, A36 and A39, which are highly expressed in pollen and pollen tubes. a36 and a36 a39 mutants display significantly reduced pollen activity. Transmission electron microscopy and terminaldeoxynucleotidyl transferase-mediated nick end labeling assays further revealed that the unviable pollen in a36 a39 may undergo unanticipated apoptosis-like programmed cell death. The degeneration of female gametes also occurred in a36 a39. Aniline Blue staining, scanning electron microscopy, and semi in vitro guidance assays indicated that the micropylar guidance of pollen tubes is significantly compromised in a36 a39. A36 and A39 that were fused with green fluorescent protein are localized to the plasma membrane and display punctate cytosolic localization and colocalize with the GPI-anchored protein COBRA-LIKE10. Furthermore, in a36 a39, the abundance of highly methylesterified homogalacturonans and xyloglucans was increased significantly in the apical pollen tube wall. These results indicate that A36 and A39, two putative GPI-anchored aspartic proteases, play important roles in plant reproduction in Arabidopsis.