Null Mutation ofAtCUL1Causes Arrest in Early Embryogenesis inArabidopsis

Abstract

The SCF (for SKP1, Cullin/CDC53, F-box protein) ubiquitin ligase targets a number of cell cycle regulators, transcription factors, and other proteins for degradation in yeast and mammalian cells. Recent genetic studies demonstrate that plant F-box proteins are involved in auxin responses, jasmonate signaling, flower morphogenesis, photocontrol of circadian clocks, and leaf senescence, implying a large spectrum of functions for the SCF pathway in plant development. Here, we present a molecular and functional characterization of plant cullins. The Arabidopsis genome contains 11 cullin-related genes. Complementation assays revealed that AtCUL1 but not AtCUL4 can functionally complement the yeast cdc53 mutant. Arabidopsis mutants containing transfer DNA (T-DNA) insertions in the AtCUL1 gene were shown to display an arrest in early embryogenesis. Consistently, both the transcript and the protein of the AtCUL1 gene were found to accumulate in embryos. The AtCUL1 protein localized mainly in the nucleus but also weakly in the cytoplasm during interphase and colocalized with the mitotic spindle in metaphase. Our results demonstrate a critical role for the SCF ubiquitin ligase in Arabidopsis embryogenesis.

CULLIN 4-RING FINGER-LIGASE plays a key role in the control of endoreplication cycles in Arabidopsis trichomes

“…Neither mutants for CUL1 nor CUL3A displayed trichomes with an altered size or DNA content (Table S3). As null mutants for these genes are not viable (40,41), it is difficult to unambiguously demonstrate whether the depletion of CULLIN activity in the hypomorphic mutants was sufficient to reveal a function during trichome development. However, a knock-down line for CUL4 produced small and dying trichomes (Fig.…”

Stability of plant immune-receptor resistance proteins is controlled by SKP1-CULLIN1-F-box (SCF)-mediated protein degradation

“…Because a mutation in SGT1b also results in increased SNC1 protein level and SGT1 associates with SKP1 and CUL1 (7,11,13), two shared members of the SCF E3 ubiquitin ligase complex, we asked whether the stability of SNC1 could be controlled by SCF-mediated protein degradation. In Arabidopsis, null mutations in CUL1 are lethal (16). A partial loss-of-function allele of CUL1, cul1-7, was found to exhibit a dwarf phenotype similar to snc1 (17) (Fig.…”

Auxin Control of Embryo Patterning

“…3C). In Arabidopsis, TIR1 functions in the SCF TIR1 complex, which consists of the F-Box-protein TIR1, the ring finger protein RBX1, the cullin protein CUL1, and one of the ASK proteins (Gray et al 2002;Shen et al 2002;Liu et al 2004). Related-to-ubiquitin (RUB) modification of the CUL1 subunit of the SCF complex is important for its function (Dharmasiri et al 2003) and involves the activity of a heterodimeric RUB activating enzyme composed of ECR1 and AXR1 or the redundantly acting AXL, a RUB conjugating enzyme RCE1 and the RBX1 protein of the SCF complex, which serves as a RUB ligase (Fig.…”