The rice RING E3 ligase, OsCTR1, inhibits trafficking to the chloroplasts of OsCP12 and OsRP1, and its overexpression confers drought tolerance in Arabidopsis.
Plant growth under low water availability adversely affects many key processes with morphological, physiological, biochemical and molecular consequences. Here, we found that a rice gene, OsCTR1, encoding the RING Ub E3 ligase plays an important role in drought tolerance. OsCTR1 was highly expressed in response to dehydration treatment and defense-related phytohormones, and its encoded protein was localized in both the chloroplasts and the cytosol. Intriguingly, the OsCTR1 protein was found predominantly targeted to the cytosol when rice protoplasts transfected with OsCTR1 were treated with abscisic acid (ABA). Several interacting partners were identified, which were mainly targeted to the chloroplasts, and interactions with OsCTR1 were confirmed by using biomolecular fluorescence complementation (BiFC). Interestingly, two chloroplast-localized proteins (OsCP12 and OsRP1) interacted with OsCTR1 in the cytosol, and ubiquitination by OsCTR1 led to protein degradation via the Ub 26S proteasome. Heterogeneous overexpression of OsCTR1 in Arabidopsis exhibited hypersensitive phenotypes with respect to ABA-responsive seed germination, seedling growth and stomatal closure. The ABA-sensitive transgenic plants also showed improvement in their tolerance against severe water deficits. Taken together, our findings lend support to the hypothesis that the molecular functions of OsCTR1 are related to tolerance to water-deficit stress via ABA-dependent regulation and related systems.
Department of Applied Plant Sciences, Kangwon National University, Chuncheon, 200-713, Korea.
Sung Don
SD
Lim
Chanhui
C
Lee
Cheol Seong
CS
Jang
D000040:Abscisic Acid / Q000494:pharmacology; D000222:Adaptation, Physiological / Q000187:drug effects / Q000235:genetics; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism*; D055864:Droughts; D005453:Fluorescence; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D008969:Molecular Sequence Data; D012275:Oryza / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D010641:Phenotype; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D030821:Plants, Genetically Modified; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D014867:Water
D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D025801:Ubiquitin; D014867:Water; D000040:Abscisic Acid; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex
ABA-dependent regulation; chloroplast protein; protein trafficking; ubiquitination