Arabidopsis ABI5 plays a role in regulating ROS homeostasis by activating CATALASE 1 transcription in seed germination

Chao Bi,Kai Lu,Zhen Wu,Yu Ma,Xiao-Fang Wang,Yong-Tao Yu,Shan Liang

doi:10.1007/s11103-017-0603-y

Abstract

It has been known that ABA INSENSITIVE 5 (ABI5) plays a vital role in regulating seed germination. In the present study, we showed that inhibition of the catalase activity with 3-amino-1,2,4-triazole (3-AT) inhibits seed germination of Col-0, abi5 mutants and ABI5-overexpression transgenic lines. Compared with Col-0, the seeds of abi5 mutants showed more sensitive to 3-AT during seed germination, while the seeds of ABI5-overexpression transgenic lines showed more insensitive. H2O2 showed the same effect on seed germination of Col-0, abi5 mutants and ABI5-overexpression transgenic lines as 3-AT. These results suggest that ROS is involved in the seed germination mediated by ABI5. Further, we observed that T-DNA insertion mutants of the three catalase members in Arabidopsis displayed 3-AT-insensitive or -hypersensitive phenotypes during seed germination, suggesting that these catalase members regulate ROS homeostasis in a highly complex way. ABI5 affects reactive oxygen species (ROS) homeostasis by affecting CATALASE expression and catalase activity. Furthermore, we showed that ABI5 directly binds to the CAT1 promoter and activates CAT1 expression. Genetic evidence supports the idea that CAT1 functions downstream of ABI5 in ROS signaling during seed germination. RNA-sequencing analysis indicates that the transcription of the genes involved in ROS metabolic process or genes responsive to ROS stress is impaired in abi5-1 seeds. Additionally, expression changes in some genes correlative to seed germination were showed due to the change in ABI5 expression under 3-AT treatment. Together, all the findings suggest that ABI5 regulates seed germination at least partly by affecting ROS homeostasis.

Highlights

Seeds are important for sustainable agriculture production and landscape biodiversity
In the presence of 3-AT, we found that compared with Col-0, the seed germination of abi5-1 or abi5-7 was much slower, revealing that abi5-1 and abi5-7 were hypersensitive to 3-AT, but the seed germination of ABA INSENSITIVE 5 (ABI5)-overexpression lines, was much faster, revealing that ABI5OE was insensitive to 3-AT (Fig. 1)
Because 3-AT is connected with catalase, we suggested that catalase probably participated in the seed germination mediated by ABI5

Summary

Introduction

Seeds are important for sustainable agriculture production and landscape biodiversity. As the first phase transition in the life cycle of higher plants, seed germination is a complex process affected by many factors. Molecular mechanisms of seed germination are largely unknown. Reactive oxygen species (ROS), including superoxide (O2−), hydrogen peroxide (H2O2), hydroxyl radical (HO), and singlet oxygen (1O2), has been believed to be connected with many biotic and abiotic stress, such as oxidative stress, drought stress, salt stress, and pathogen stress (Dat et al 2000; Apel and Hirt 2004; Laloi et al 2004; Torres and Dangl 2005; Miller et al 2008). New evidence suggests that ROS is a cytotoxic molecule, and emerges as a key regulator in seed physiology where ROS mediates seed germination (Bailly 2004; El-Maarouf-Bouteau et al 2007; Bailly et al 2008; Ye et al 2012). An optimal range of ROS level is required for successful germination

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Results

Conclusion