Mutations in the Rice OsCHR4 Gene, Encoding a CHD3 Family Chromatin Remodeler, Induce Narrow and Rolled Leaves with Increased Cuticular Wax.

Tingting Guo,Daofeng Wang,Xueyong Li,Jingjing Fang,Jinfeng Zhao,Langtao Xiao,Shoujiang Yuan

doi:10.3390/ijms20102567

Abstract

Leaf blade width, curvature, and cuticular wax are important agronomic traits of rice. Here, we report the rice Oschr4-5 mutant characterized by pleiotropic phenotypes, including narrow and rolled leaves, enhanced cuticular wax deposition and reduced plant height and tiller number. The reduced leaf width is caused by a reduced number of longitudinal veins and increased auxin content. The cuticular wax content was significantly higher in the Oschr4-5 mutant, resulting in reduced water loss rate and enhanced drought tolerance. Molecular characterization reveals that a single-base deletion results in a frame-shift mutation from the second chromodomain of OsCHR4, a CHD3 (chromodomain helicase DNA-binding) family chromatin remodeler, in the Oschr4-5 mutant. Expressions of seven wax biosynthesis genes (GL1-4, WSL4, OsCER7, LACS2, LACS7, ROC4 and BDG) and four auxin biosynthesis genes (YUC2, YUC3, YUC5 and YUC6) was up-regulated in the Oschr4-5 mutant. Chromatin immunoprecipitation assays revealed that the transcriptionally active histone modification H3K4me3 was increased, whereas the repressive H3K27me3 was reduced in the upregulated genes in the Oschr4-5 mutant. Therefore, OsCHR4 regulates leaf morphogenesis and cuticle wax formation by epigenetic modulation of auxin and wax biosynthetic genes expression.

Highlights

In plants, leaves are the major organ used for photosynthesis and transpiration, and are considered to be the main source of dry matter accumulation in plants
A rice mutant characterized by narrow and rolled leaves was isolated from the gamma ray mutagenized Indica rice cultivar Indica 9, which was named as Oschr4-5 based on the gene identity revealed in the following study
To understand why the content of cuticular wax increased in the Oschr4-5 mutant, we examined the expression levels of 16 genes encoding enzymes involved in wax biosynthesis and three genes (ROC4, WR1, WR2) encoding transcription factors that activate the expression of wax biosynthetic genes [26,27,28,44,45]

Summary

Introduction

Leaves are the major organ used for photosynthesis and transpiration, and are considered to be the main source of dry matter accumulation in plants. Mutations in genes involved in other pathways could produce narrow leaves such as NAL9 (encoding an ATP-dependent Clp protease proteolytic subunit) and NAL11 (encoding a heat shock DNAJ protein) [8,9]. For rolled leave, it could be divided into adaxialized and abaxialized curling. The mutant of SLL1/RL9 (encoding a SHAQKYF class MYB family transcription factor) displayed completely adaxialized leaves [10] This gene mainly functions in the modulation of sclerenchymatous cells formation on the abaxial side during leaf development [11]. The mutants of NRL1 (encoding cellulose synthase-like protein D4), NRL2 and NRL3 (both encoding a novel protein with unknown biochemical function) could induce semi-rolled leaves with reduced blade width [16,17,18,19]

Methods

Results

Conclusion