Control of seed dormancy and germination by DOG1-AHG1 PP2C phosphatase complex via binding to heme

Noriyuki Nishimura,Toshimasa Yamazaki,Yuki Hayashi,Julian I Schroeder,Tomoko Irisa,Takashi Hirayama,John R Yates,Nahomi Kaiwa,Kouji Satoh,Wataru Tsuchiya,Toshinori Kinoshita,James J Moresco

doi:10.1038/s41467-018-04437-9

Abstract

Abscisic acid (ABA) regulates abiotic stress and developmental responses including regulation of seed dormancy to prevent seeds from germinating under unfavorable environmental conditions. ABA HYPERSENSITIVE GERMINATION1 (AHG1) encoding a type 2C protein phosphatase (PP2C) is a central negative regulator of ABA response in germination; however, the molecular function and regulation of AHG1 remain elusive. Here we report that AHG1 interacts with DELAY OF GERMINATION1 (DOG1), which is a pivotal positive regulator in seed dormancy. DOG1 acts upstream of AHG1 and impairs the PP2C activity of AHG1 in vitro. Furthermore, DOG1 has the ability to bind heme. Binding of DOG1 to AHG1 and heme are independent processes, but both are essential for DOG1 function in vivo. Our study demonstrates that AHG1 and DOG1 constitute an important regulatory system for seed dormancy and germination by integrating multiple environmental signals, in parallel with the PYL/RCAR ABA receptor-mediated regulatory system.

Highlights

Abscisic acid (ABA) regulates abiotic stress and developmental responses including regulation of seed dormancy to prevent seeds from germinating under unfavorable environmental conditions
To assess whether Pyrabactin Resistance 1 (PYR1) was able to interact with all nine group A PP2Cs including ABA HYPERSENSITIVE GERMINATION1 (AHG1), which we previously identified as a central negative regulator of ABA signaling in seeds (Supplementary Fig. 1a)[36], we performed yeast two-hybrid assays (Fig. 1a)
With the exception of HAI2/ AIP1, YFP fused to AHG1 subfamily members predominantly localized in the nucleus when transiently expressed in N. benthamiana protoplasts, whereas YFP fused to all the ABI1 subfamily members and HAI2/AIP1 were observed in the cytoplasm and the nucleus, consistent with the results from the previous report (Supplementary Fig. 1b)[19]

Summary

Introduction

Abscisic acid (ABA) regulates abiotic stress and developmental responses including regulation of seed dormancy to prevent seeds from germinating under unfavorable environmental conditions. ABA HYPERSENSITIVE GERMINATION1 (AHG1) encoding a type 2C protein phosphatase (PP2C) is a central negative regulator of ABA response in germination; the molecular function and regulation of AHG1 remain elusive. ABA regulates abiotic stress and developmental responses including seed maturation, regulation of seed dormancy and germination, growth regulation, and stomatal closure[6,7], and has recently been shown to transiently elevate heme levels[8,9]. DELAY OF GERMINATION1 (DOG1) encodes a protein of unknown biochemical function and was first identified in Arabidopsis as a major quantitative trait locus (QTL) for an increase in seed dormancy[12]. The ABI1 subfamily is formed by ABI1, ABI2, HYPERSENSITIVE TO ABA1 (HAB1) and HAB2, while AHG1 subfamily is formed by AHG1, AHG3/PROTEIN

Methods

Results

Conclusion