title: A Kunitz-type protease inhibitor regulates programmed cell death during flower development in Arabidopsis thaliana.
abstract: Flower development and fertilization are tightly controlled in Arabidopsis thaliana. In order to permit the fertilization of a maximum amount of ovules as well as proper embryo and seed development, a subtle balance between pollen tube growth inside the transmitting tract and pollen tube exit from the septum is needed. Both processes depend on a type of programmed cell death that is still poorly understood. Here, it is shown that a Kunitz protease inhibitor related to water-soluble chlorophyll proteins of Brassicaceae (AtWSCP, encoded by At1g72290) is involved in controlling cell death during flower development in A. thaliana. Genetic, biochemical, and cell biology approaches revealed that WSCP physically interacts with RD21 (RESPONSIVE TO DESICCATION) and that this interaction in turn inhibits the activity of RD21 as a pro-death protein. The regulatory circuit identified depends on the restricted expression of WSCP in the transmitting tract and the septum epidermis. In a respective Atwscp knock-out mutant, flowers exhibited precocious cell death in the transmitting tract and unnatural death of septum epidermis cells. As a consequence, apical-basal pollen tube growth, fertilization of ovules, as well as embryo development and seed formation were perturbed. Together, the data identify a unique mechanism of cell death regulation that fine-tunes pollen tube growth.
authors.affiliation: Laboratoire de Génétique Moléculaire des Plantes and Biologie Environnementale et Systémique (BEeSy), Université Joseph Fourier, LBFA, BP53F, 38041 Grenoble cedex 9, France.
authors.forename: Edouard
authors.initials: E
authors.lastname: Boex-Fontvieille
authors.affiliation: Molecular Plant Sciences, Department of Crop and Soil Sciences, Washington State University, Pullman WA 99164-6420, USA.
authors.forename: Sachin
authors.initials: S
authors.lastname: Rustgi
authors.affiliation: Laboratoire de Génétique Moléculaire des Plantes and Biologie Environnementale et Systémique (BEeSy), Université Joseph Fourier, LBFA, BP53F, 38041 Grenoble cedex 9, France sreinbot@ujf-grenoble.fr.
authors.forename: Steffen
authors.initials: S
authors.lastname: Reinbothe
authors.affiliation: University of Bayreuth, Universitätsstraße 30, D-95440 Bayreuth, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Reinbothe
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D016923:Cell Death; D061146:Chlorophyll Binding Proteins / Q000235:genetics* / Q000378:metabolism; D057056:Cysteine Proteases / Q000235:genetics* / Q000378:metabolism; D035264:Flowers / Q000254:growth & development / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D012639:Seeds / Q000254:growth & development; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C586527:At3g57670 protein, Arabidopsis; D061146:Chlorophyll Binding Proteins; C587998:HECATE1 protein, Arabidopsis; D014157:Transcription Factors; C576738:WSCP protein, Arabidopsis; D057056:Cysteine Proteases; C549570:RD21 protein, Arabidopsis
keywords: Cell death; RD21 (RESPONSIVE TO DESICCATION 21); WSCP (water-soluble chlorophyll-binding protein).; flower development; protease inhibitors; transmitting tract