Formin protein DRT1 affects gross morphology and chloroplast relocation in rice

Abstract

Plant height and tiller number are two major factors determining plant architecture and yield. However, in rice (Oryza sativa), the regulatory mechanism of plant architecture remains to be elucidated. Here we reported a recessive rice mutant presenting dwarf and reduced tillering phenotypes (drt1). Map-based cloning revealed that the phenotypes are caused by a single point mutation in DRT1, which encodes the class I formin protein Oryza sativa formin homolog 13 (OsFH13), binds with F-actin, and promotes actin polymerization for microfilament organization. DRT1 protein localized on the plasma membrane and chloroplast outer envelope. DRT1 interacted with rice phototropin 2 (OsPHOT2), and the interaction was interrupted in drt1. Upon blue light stimulus, plasma membrane localized DRT1 and OsPHOT2 were translocated onto the chloroplast membrane. Moreover, deficiency of DRT1 reduced OsPHOT2 internalization and OsPHOT2-mediated chloroplast relocation. Our study suggests that rice formin protein DRT1/OsFH13 is necessary for plant morphology and chloroplast relocation by modulating the actin-associated cytoskeleton network.

Transmembrane formins as active cargoes of membrane trafficking

“…While not directly related to membrane trafficking as such, another class I formin, rice OsFH13/DRT, whose mutation causes a pleiotropic cell growth defect resulting in dwarf plant stature and reduced tillering ( Ren et al , 2022 ), also migrates between cellular membranes, relocating from the plasmalemma to the chloroplast envelope in mesophyll cell protoplasts in response to a blue light stimulus. This movement depends on physical interaction between the formin’s FH1 domain and the LOV2 domain of the blue light receptor phototropin, which was documented by yeast two-hybrid assays, as well as by split luciferase assays and co-immunoprecipitation ( Y. Zhang et al , 2023 ).…”

Exploring the Role of the Plant Actin Cytoskeleton: From Signaling to Cellular Functions

“…FH2 regulates PD permeability by anchoring actin filaments to PD, which is crucial for normal intercellular trafficking [144]. In addition, rice formin protein OsFH13 is a putative traffic protein from the PM to the chloroplast membrane and bridges the actin cytoskeleton and light signaling [145]. A central mechanism in plant immune signaling suggests that rapid actin remodeling occurs through the nanoclustering of formin integrated into the PM [146,147].…”

Imaging of Chloroplast Movement Responses to Light Stimulation in Different Intensities in Rice

“…In this protocol, we describe a method to detect chloroplast movement using rice leaf sheath. The method is based on a protocol established for Arabidopsis and rice ( Zhang et al, 2022 ), which we have adapted and optimized for convenient and accurate analysis of rice and other gramineous plants. There is no doubt that the system will be beneficial for further understanding of the molecular mechanisms and evolutionary history of chloroplast movement in green plants.…”