Abstract
Ubiquitination is an important post-translational protein modification that is known to play critical roles in diverse biological processes in eukaryotes. The RING E3 ligases function in ubiquitination pathways, and are involved in a large diversity of physiological processes in higher plants. The RING domain-containing E3 ligase AtRDUF1 was previously identified as a positive regulator of ABA-mediated dehydration stress response in Arabidopsis. In this study, we report that AtRDUF1 is involved in plant responses to salt stress. AtRDUF1 expression is upregulated by salt treatment. Overexpression of AtRDUF1 in Arabidopsis results in an insensitivity to salt and osmotic stresses during germination and seedling growth. A double knock-out mutant of AtRDUF1 and its close homolog AtRDUF2 (atrduf1atrduf2) was hypersensitive to salt treatment. The expression levels of the stress-response genes RD29B, RD22, and KIN1 are more sensitive to salt treatment in AtRDUF1 overexpression plants. In summary, our data show that AtRDUF1 positively regulates responses to salt stress in Arabidopsis.
Highlights
Ubiquitination is a mechanism of post-translational regulation
The RING domain subfamily of E3s is large in Arabidopsis and can be further divided into single subunit RING E3s, such as Constitutive Photomorphogenesis1 (COP1) [4], SEVEN IN ABSENTIA IN ARABIDOPSIS THALIANA 5 (SINAT5) [5], and Arm Repeat-Containing 1 (ARC1) [6], and multisubunit RING E3s including the SCF, CUL3-BTB, and APC complexes [7]
At5g59550 and At3g46620 were previously designated as AtRDUF2 and AtRDUF1, respectively [19]
Summary
Ubiquitination is a mechanism of post-translational regulation. The ubiquitination cascade is catalyzed by ubiquitin-activating enzyme (E1), ubuiquitin-conjugating enzyme (E2) and ubiquitin protein ligase (E3). There are .1300 predicted E3 ligases in the Arabidopsis genome, including .450. The vast majority of E3 uibiquitin ligases in the Arabidopsis genome facilitate the identification of specific substrates and their subsequent ubiquitination [1,3]. The E3 ubiquitin ligases are a huge and varied family of proteins and protein complexes which contain either a HECT domain or a U-box/RING domain. The HECT domain subfamily of E3s is relatively small in Arabidopsis. The RING domain subfamily of E3s is large in Arabidopsis and can be further divided into single subunit RING E3s, such as Constitutive Photomorphogenesis (COP1) [4], SEVEN IN ABSENTIA IN ARABIDOPSIS THALIANA 5 (SINAT5) [5], and Arm Repeat-Containing 1 (ARC1) [6], and multisubunit RING E3s including the SCF, CUL3-BTB, and APC complexes [7]. E3 ligases are involved in various aspects of plant biological processes, including growth, development, and protection from biotic and abiotic stresses [11,12]
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