Arabidopsis RIC1 Severs Actin Filaments at the Apex to Regulate Pollen Tube Growth. Issue 4 (24th March 2015)

• Record Type: Journal Article
• Authors: Zhou, Zhenzhen; Shi, Haifan; Chen, Binqing; Zhang, Ruihui; Huang, Shanjin; Fu, Ying
• Is Part Of: The Plant Cell. Volume 27:Issue 4(2015)
• Page Start: 1140
• Page End: 1161
• Publication Date: 2015-03-24
• DOI: 10.1105/tpc.114.135400
• Languages: English
• ISSNs: 1040-4651

Abstract

Abstract : RIC1 regulates pollen tube growth through its F-actin severing and capping activities, which contributes to the dynamics and abundance of F-actin in the tip of pollen tubes. Abstract: Pollen tubes deliver sperms to the ovule for fertilization via tip growth. The rapid turnover of F-actin in pollen tube tips plays an important role in this process. In this study, we demonstrate that Arabidopsis thaliana RIC1, a member of the ROP-interactive CRIB motif-containing protein family, regulates pollen tube growth via its F-actin severing activity. Knockout of RIC1 enhanced pollen tube elongation, while overexpression of RIC1 dramatically reduced tube growth. Pharmacological analysis indicated that RIC1 affected F-actin dynamics in pollen tubes. In vitro biochemical assays revealed that RIC1 directly bound and severed F-actin in the presence of Ca 2+ in addition to interfering with F-actin turnover by capping F-actin at the barbed ends. In vivo, RIC1 localized primarily to the apical plasma membrane (PM ) of pollen tubes. The level of RIC1 at the apical PM oscillated during pollen tube growth. The frequency of F-actin severing at the apex was notably decreased in ric1-1 pollen tubes but was increased in pollen tubes overexpressing RIC1. We propose that RIC1 regulates F-actin dynamics at the apical PM as well as the cytosol by severing F-actin and capping the barbed ends in the cytoplasm, establishing a novel mechanism that underlies the regulation of pollen tube growth.