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Arabidopsis DDB1-CUL4 E3 ligase complexes in det1 salt/osmotic stress resistant germination.

ABSTRACT: A key regulatory mechanism in plant growth, development, and stress signaling utilizes E3 ubiquitin ligases, which target a variety of substrates for degradation. DE-ETIOLATED 1 (DET1) forms a complex with DDB1 (DAMAGED DNA BINDING protein 1) and CUL4 (CULLIN 4), and negatively regulates light signaling. Another DDB1-CUL4 complex containing DWA1 and DWA2 (DWD hypersensitive to ABA 1 and 2) has been shown to negatively regulate abscisic acid (ABA) signaling. Since distinct DDB1-CUL4 complexes have been shown to influence each other, we analyzed genetic interactions between DET1 and components of DDB1-CUL4 complexes during seed germination under salt and osmotic stress conditions. det1 germination was resistant to salt and osmotic stress and dwa1 and dwa2 enhanced this phenotype. In contrast, ddb1a partially suppressed the det1 germination phenotype on both salt and mannitol, while ddb1b had no effect. Mutations in DDB2, a DDB1-CUL4 complex component involved in DNA repair, also partially suppressed the det1 germination phenotype while mutants in COP1, another light signaling component, completely suppressed the det1 resistant germination phenotypes. Taken together these data suggest that components of E3 ubiquitin ligase complexes have variable but significant effects on det1 salt/osmotic stress responses.

SUBMITTER: Fernando VC

PROVIDER: S-EPMC5058461 | biostudies-other | 2016 Sep

REPOSITORIES: biostudies-other

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Project description:BackgroundWater and salt stresses are two important environmental factors that limit the germination of seeds in most ecological environments. Most studies conducted so far to address the genetic basis of the above phenomenon have used stress conditions that are much more extreme than those found in natural environments. Furthermore, although an excess of ions and water restrictions have similar osmotic effects on germination, the common and divergent signalling components mediating the effects of both factors remain unknown.MethodsThe germination of seeds was compared under solutions of NaCl (50 mm) and polyethylene glycol (PEG, -0·6 MPa), that establish mild stress conditions, in 28 Arabidopsis thaliana accessions. Because Bayreuth (Bay) and Shadara (Sha) accessions showed contrasting sensitivity responses to both stresses, a quantitative trait locus (QTL) analysis was carried out using Bay × Sha recombinant inbred lines (RILs) to identify loci involved in the control of germination under mild salt and osmotic stresses.Key resultsTwo loci associated with the salt sensitivity response, named SSR1 and SSR2 QTLs, and four loci for the osmotic sensitivity response, named OSR1-OSR4 QTLs, were mapped. The effects of the SSR1 QTL on toxic salt sensitivity, and the osmotic contribution of OSR1, were confirmed by heterogeneous inbred families (HIFs). Whilst the SSR1 QTL had a significant effect under a wide range of NaCl concentrations, the OSR1 QTL was confirmed only under moderate drought stress. Interestingly the OSR1 QTL also showed pleiotropic effects on biomass accumulation in response to water deficit.ConclusionsThe regulation of germination under moderate salt and osmotic stresses involves the action of independent major loci, revealing the existence of loci specifically associated with the toxic component of salt and not just its osmotic effect. Furthermore, this work demonstrates that novel loci control germination under osmotic stress conditions simulating more realistic ecological environments as found by populations of seeds in nature.

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Arabidopsis DDB1-CUL4 E3 ligase complexes in det1 salt/osmotic stress resistant germination.

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