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Cover -- Half Title -- Title Page -- Copyright Page -- Contents -- Introduction to the Transaction Edition -- Foreword -- Preface -- Acknowledgments -- PART ONE: The Problem of Regulatory Unreasonableness -- Chapter One: The Growth of Protective Regulation -- Chapter Two: Toward Toughness: The Changing Legal Structure of Enforcement -- Chapter Three: Unreasonableness -- Chapter Four: The Perverse Effects of Legalism -- PART TWO: Flexible Enforcement and Its Limits -- Chapter Five: The Good Inspector -- Chapter Six: Managing the Regulatory Agency -- Chapter Seven: The Regulatory Ratchet -- PART THREE: Indirect Regulation -- Chapter Eight: Private Regulation -- Chapter Nine: Mandatory Disclosure -- Chapter Ten: Liability -- Chapter Eleven: The Social Responsibility of Government -- Notes -- Index

Cell and tissue polarization is fundamental for plant growth and morphogenesis. The polar, cellular localization ofArabidopsisPIN-FORMED (PIN) proteins is crucial for their function in directional auxin transport. The clustering of PIN polar cargoes within the plasma membrane has been proposed to be important for the maintenance of their polar distribution. However, the more detailed features of PIN clusters and the cellular requirements of cargo clustering remain unclear. Here, we characterized PIN clusters in detail by means of multiple advanced microscopy and quantification methods, such as 3D quantitative imaging or freeze-fracture replica labeling. The size and aggregation types of PIN clusters were determined by electron microscopy at the nanometer level at different polar domains and at different developmental stages, revealing a strong preference for clustering at the polar domains. Pharmacological and genetic studies revealed that PIN clusters depend on phosphoinositol pathways, cytoskeletal structures and specific cell-wall components as well as connections between the cell wall and the plasma membrane. This study identifies the role of different cellular processes and structures in polar cargo clustering and provides initial mechanistic insight into the maintenance of polarity in plants and other systems. ; European Research Council (ERC) 742985 Comision Nacional de Investigacion Cientifica y Tecnologica CONICYT-PAI 82130047 European Union (EU) 291734