Arabidopsis Histone Methyltransferase SUVH5 Is a Positive Regulator of Light-Mediated Seed Germination.

Dachuan Gu,Chunmei He,Mingyong Zhang,Tao Peng,Jun Duan,Rujun Ji,Changyun Xiong,Xuncheng Liu

doi:10.3389/fpls.2019.00841

Abstract

Plant lifecycle starts from seed germination, which is regulated by various environmental cues and endogenous hormones. Light promotes seed germination mainly by phytochrome B (PHYB) during the initial phase of imbibition, which involves genome-wide light-responsive transcription changes. Recent studies indicated an involvement of multiple epigenetic factors in the control of seed germination. However, few studies have been reported about the role of a histone methyltransferase in light-mediated seed germination process. Here, we identified SUVH5, a histone H3 lysine 9 methyltransferase, as a positive regulator in light-mediated seed germination in Arabidopsis. Loss of function of SUVH5 leads to decreased PHYB-dependent seed germination. RNA-sequencing analysis displayed that SUVH5 regulates 24.6% of light-responsive transcriptome in imbibed seeds, which mainly related to hormonal signaling pathways and developmental processes. Furthermore, SUVH5 represses the transcription of ABA biosynthesis and signal transduction-related genes, as well as a family of DELAY OF GERMINATION (DOG) genes via dimethylation of histone H3 at lysine 9 (H3K9me2) in imbibed seeds. Taken together, our findings revealed that SUVH5 is a novel positive regulator of light-mediated seed germination in Arabidopsis.

Highlights

Plant life cycle initiates from seed germination, which is of both economic and ecologic importance (Rajjou et al, 2012)
To investigate whether histone methyltransferase SUVH5 plays a role in light-regulated seed germination, we examined the germination trait of a previously reported loss of function of SUVH5 mutant suvh5-2 (Ebbs and Bender, 2006) by PHYBdependent germination protocol (Oh et al, 2004; Oh et al, 2006). 1 h after white light (WL) irradiation and surface sterilization, the seeds were exposed to 5 min far-red (FR) light (PHYB inactive, referred as far-red light (FR) or dark conditions) or followed by illumination with 5 min red light (PHYB activation, indicated as R or light conditions), and subsequently kept in the dark for 2 days (Figure 1A)
We present evidence indicating that SUVH5 is a positive component of light-mediated seed germination process

Summary

Introduction

Plant life cycle initiates from seed germination, which is of both economic and ecologic importance (Rajjou et al, 2012). Arabidopsis seeds consist of embryo, single cell endosperm and testa from inside to outside (Finch-Savage and Leubner-Metzger, 2006). Arabidopsis seed germination includes two-step process, which is testa rupture followed by endosperm rupture (Yamaguchi, 2008; Weitbrecht et al, 2011). It is well known that seed germination is regulated by endogenous and exogenous factors, such as light, temperature, moisture, oxygen, nutrients, and multiple plant hormones (Finch-Savage and Leubner-Metzger, 2006; De Wit et al, 2016; Shu et al, 2016). Phytochromes are red and farred light photoreceptors that play critical role in regulating seed germination in various plants species (Borthwick et al, 1952; Shinomura et al, 1994, 1996). PHYB plays a fundamental role in the promotion of seed germination during the initiate phase of seed imbibition (Shinomura et al, 1994; Seo et al, 2008)

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Conclusion