Arabidopsis CUL3A and CUL3B genes are essential for normal embryogenesis

Abstract

). † These authors contributed equally to this work. SummaryCullin (CUL)-dependent ubiquitin ligases form a class of structurally related multisubunit enzymes that control the rapid and selective degradation of important regulatory proteins involved in cell cycle progression and development, among others. The CUL3-BTB ligases belong to this class of enzymes and despite recent findings on their molecular composition, our knowledge on their functions and substrates remains still very limited. In contrast to budding and fission yeast, CUL3 is an essential gene in metazoans. The model plant Arabidopsis thaliana encodes two related CUL3 genes, called CUL3A and CUL3B. We recently reported that cul3a loss-offunction mutants are viable but exhibit a mild flowering and light sensitivity phenotype. We investigated the spatial and temporal expression of the two CUL3 genes in reproductive tissues and found that their expression patterns are largely overlapping suggesting possible functional redundancy. Thus, we investigated the consequences on plant development of combined Arabidopsis cul3a cul3b loss-of-function mutations. Homozygous cul3b mutant plants developed normally and were fully fertile. However, the disruption of both the CUL3A and CUL3B genes reduced gametophytic transmission and caused embryo lethality. The observed embryo abortion was found to be under maternal control. Arrest of embryogenesis occurred at multiple stages of embryo development, but predominantly at the heart stage. At the cytological level, CUL3 loss-of-function mutations affected both embryo pattern formation and endosperm development.

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.…”

CUL4 forms an E3 ligase with COP1 and SPA to promote light-induced degradation of PIF1

“…The plates were kept at 4°C in the dark for 3 to 4 days to stratify and then exposed to 3 h of white light at room temperature before being placed in the dark for 21 h. The plates were incubated at 21°C for an additional 3 days in the dark or light as indicated. Arabidopsis thaliana wild type and various mutants (pif1, cop1-4, cop1-6, spa1, spa2, spa12, spa123, spa124, spaQ, cul1-6, cul3a, cul3b, cul3ab, cul4-1 and cul4cs) in the Col-0 background were used 6,32,[40][41][42][43][44][45][46][47][48] . For generation of different spaQpif1 mutant, pif1 and spaQ were crossed to obtain the F1 seeds.…”

The E3 Ubiquitin Ligase Gene Family in Plants: Regulation by Degradation

“…CUL3A and CUL3B appear functional redundant, since cul3a and cul3b mutants are viable and, consistently, they have largely overlapping expression patterns. However, the disruption of both the CUL3A and CUL3B genes affected both embryo pattern formation and endosperm development, causing embryo lethality [44,45,78]. Although arrest at the heart stage was predominant, block of embryogenesis occurring at multiple stages of embryo development indicated a general growth inhibition of the embryo.…”