The F-box protein ZEITLUPE controls stability and nucleocytoplasmic partitioning of GIGANTEA

Wang

Proc. Natl. Acad. Sci. U.S.A.

et al. 2013

Self Cite

Significance Plants rely on many different types of photoreceptors to control light responses, but the molecular mechanisms underlying the coaction of different photoreceptors that regulate the same light response remains unclear. This study demonstrates a mechanism of the photoreceptor coaction. In Arabidopsis , the blue-light receptor cryptochrome 2 interacts with and activates the transcription factor CRYPTOCHROME-INTERACTING basic helix–loop–helix 1 (CIB1). It was found that CIB1 protein is degraded in the absence of blue light and that the light–oxygen–voltage-domain F-box blue-light receptor ZEITLUPE mediates blue-light suppression of CIB1 degradation.

Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 89%

Arabidopsis CRY2 and ZTL mediate blue-light regulation of the transcription factor CIB1 by distinct mechanisms

Wang

Proc. Natl. Acad. Sci. U.S.A.

et al. 2013

Self Cite

“…This interaction is blue-light dependent and stabilizes ZTL protein (Kim et al 2007). Production of ZTL LOV in transgenic Arabidopsis causes period lengthening under red-or blue-light conditions, similar to ztl loss-of-function mutations, and a decreased level of endogenous ZTL protein compared to that in the control (Kim et al 2013;Somers et al 2000). These results suggest that production of ZTL LOV reduces endogenous ZTL protein stability by interfering with the interaction between endogenous ZTL and GI, and that the reduction in ZTL levels leads to period lengthening.…”

mentioning

confidence: 72%

“…Furthermore, production of ZTL LOV results in elongated hypocotyls under red-or bluelight conditions and in delayed flowering under LD conditions, similar to overproduction of ZTL (Kiyosue and Wada 2000;Somers et al 2004). These phenotypes are postulated to be caused by the inhibition of GI functions in nuclei due to enhancement of cytosolic GI distribution caused by the ZTL LOV-GI complex (Kim et al 2013).…”

mentioning

confidence: 99%

Pleiotropic phenotype of transgenic <i>Arabidopsis</i> plants that produce the LOV domain of LOV KELCH PROTEIN2 (LKP2)

Takase

Miyazaki

Yasuhara

et al. 2015

Plant Biotechnology

LOV KELCH PROTEIN2 (LKP2) is a blue-light receptor protein composed of three functional domains: a light, oxygen, or voltage (LOV) domain, an F-box motif (F), and Kelch repeats. LKP2 is postulated to be a component of an SCF complex and function in ubiquitination of proteins that control the circadian clock and photoperiodic flowering. Transgenic Arabidopsis plants that produce LOV, F, or a combination of LOV and F fused to green fluorescent protein (named GL, GF, and GLF, respectively) were produced using constructs containing the Cauliflower mosaic virus 35S promoter. Under continuous white light, the circadian rhythms of control and GF plants were similar, whereas those of GL and GLF plants were shorter. Under continuous red light, the hypocotyl lengths of control and GF seedlings were similar, whereas that of GL seedlings was longer. Late flowering and down-regulation of CONSTANS and FLOWERING LOCUS T were observed in GL and GLF plants compared to GF and control plants under long-day conditions. These results suggest that the previously reported pleiotropic phenotype of LKP2-overproducing plants, which show altered circadian rhythm, hypocotyl elongation, and photoperiodic flowering, is not only due to the promotion of ubiquitination and subsequent degradation of substrate proteins of the SCF LKP2 complex but may also be due to the functional disruption of regulatory proteins that interact with LKP2 LOV.

Proc. Natl. Acad. Sci. U.S.A.

“…The conformational shift in ZTL that follows the cessation of blue light signaling after dusk releases GI, freeing ZTL to interact with and thereby target critical clock transcriptional repressors, TOC1 and PRR5, for ubiquitylation and proteasomal degradation (40,41). Because ZTL is a cytoplasmic protein, the ZTL-GI interaction also retains GI in the cytosol, thereby limiting the nuclear accumulation of GI and antagonizing its roles in flowering timing and regulation of hypocotyl length (42).…”

Section: Gi Was First Identified As a Supervital Mutant Of Arabidopsismentioning

confidence: 99%

Allelic polymorphism of GIGANTEA is responsible for naturally occurring variation in circadian period in Brassica rapa

Xie

Lou

Hermand

et al. 2015

GIGANTEA (GI) was originally identified by a late-flowering mutant in Arabidopsis, but subsequently has been shown to act in circadian period determination, light inhibition of hypocotyl elongation, and responses to multiple abiotic stresses, including tolerance to high salt and cold (freezing) temperature. Genetic mapping and analysis of families of heterogeneous inbred lines showed that natural variation in GI is responsible for a major quantitative trait locus in circadian period in Brassica rapa. We confirmed this conclusion by transgenic rescue of an Arabidopsis gi-201 loss of function mutant. The two B. rapa GI alleles each fully rescued the delayed flowering of Arabidopsis gi-201 but showed differential rescue of perturbations in red light inhibition of hypocotyl elongation and altered cold and salt tolerance. The B. rapa R500 GI allele, which failed to rescue the hypocotyl and abiotic stress phenotypes, disrupted circadian period determination in Arabidopsis. Analysis of chimeric B. rapa GI alleles identified the causal nucleotide polymorphism, which results in an amino acid substitution (S264A) between the two GI proteins. This polymorphism underlies variation in circadian period, cold and salt tolerance, and red light inhibition of hypocotyl elongation. Loss-of-function mutations of B. rapa GI confer delayed flowering, perturbed circadian rhythms in leaf movement, and increased freezing and increased salt tolerance, consistent with effects of similar mutations in Arabidopsis. Collectively, these data suggest that allelic variation of GI-and possibly of clock genes in general-offers an attractive target for molecular breeding for enhanced stress tolerance and potentially for improved crop yield.abiotic stress tolerance | circadian clock | hypocotyl elongation | flowering time | natural variation T he last half-century has seen dramatic increases in agricultural productivity. Despite the approximate doubling in world population since 1964, the proportion with insufficient food has dropped by ∼75%, although ∼1 billion remain underfed, and twice that many suffer from micronutrient deficiencies (1). Predicted growth in population and in per capita consumption will require an estimated doubling of crop production by 2050 (2). However, yield trends for maize, rice, wheat, and soybean-four major crops that currently produce nearly two-thirds of global agricultural calories-are insufficient to achieve this doubling (3). Therefore, there is a pressing need not simply to sustain, but actually to accelerate yield improvement.One strategy to increase yield is to identify genetic variation in plant regulatory networks that limit yield to define targets for programs of marker-assisted (molecular) breeding. The circadian clock has been implicated as a target for increasing yield (4-6). Plant circadian clocks comprise multiple interlocked feedback loops (7-9). There is natural variation in clock function in both weedy and cultivated species (10-15), although few of the genes responsible for these quantitative trait loc...