The Arabidopsis APC4 subunit of the anaphase‐promoting complex/cyclosome (APC/C) is critical for both female gametogenesis and embryogenesis

Abstract

SUMMARYThe anaphase-promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase that is involved in regulating cell-cycle progression. It has been widely studied in yeast and animal cells, but the function and regulation of the APC/C in plant cells are largely unknown. The Arabidopsis APC/C comprises at least 11 subunits, only a few of which have been studied in detail. APC4 is proposed to be a connector in the APC/C in yeast and animals. Here, we report the functional characterization of the Arabidopsis APC4 protein. We examined three heterozygous plant lines carrying apc4 alleles. These plants showed pleiotropic developmental defects in reproductive processes, including abnormal nuclear behavior in the developing embryo sac and aberrant cell division in embryos; these phenotypes differ from those reported for mutants of other subunits. Some ovules and embryos of apc4/+ plants also accumulated cyclin B protein, a known substrate of APC/C, suggesting a compromised function of APC/C. Arabidopsis APC4 was expressed in meristematic cells of seedlings, ovules in pistils and embryos in siliques, and was mainly localized in the nucleus. Additionally, the distribution of auxin was distorted in some embryos of apc4/+ plants. Our results indicate that Arabidopsis APC4 plays critical roles in female gametogenesis and embryogenesis, possibly as a connector in APC/C, and that regulation of auxin distribution may be involved in these processes.

SAMBA, a plant-specific anaphase-promoting complex/cyclosome regulator is involved in early development and A-type cyclin stabilization

“…Mutations in most APC/C subunits affect female and/or male gametogenesis (24)(25)(26)(27)(28)(29). Here, we show that samba is defective in mitosis I of pollen development, resulting in pollen without sperm nuclei.…”

“…In all cases, except for APC8, the analysis of the mutants revealed female gametophytic defects, probably as a consequence of the inability to degrade mitotic cyclins (24)(25)(26)(27)(28). APC8 was shown to be involved in male gametogenesis (29).…”

“…APC8 was shown to be involved in male gametogenesis (29). Moreover, reduced expression levels of APC6 (10) or APC10 (10, 28) exhibited several developmental abnormalities, including defects in vascular development, whereas an APC4 loss-of-function mutant was defective in embryogenesis (26). APC3b (CDC27b) has a role in the maintenance of cell division in meristems during postembryonic development (30), and overexpression of APC10 enhances cell division and accelerates the degradation of the mitotic CYCB1;1, leading to increased leaf sizes (28).…”

Interregulation of CDKA/CDK1 and the Plant-Specific Cyclin-Dependent Kinase CDKB in Control of the Chlamydomonas Cell Cycle

“…Because CDKA1 activity was independent of cyclin B (see above), the APC may inactivate CDKA1 at the end of the cell cycle by targeting cyclin A for destruction. Consistently, in Arabidopsis, mutation of APC subunits slows degradation of a destruction box reporter (Kwee and Sundaresan 2003;Wang et al 2012). …”

Arabidopsis Voltage-Dependent Anion Channel 1 (AtVDAC1) Is Required for Female Development and Maintenance of Mitochondrial Functions Related to Energy-Transaction

“…Genetic analyses were then used to investigate the reason of the reduced seed set. Firstly, reciprocal crosses between homozygous atvdac1 and wild type were performed according to the approach described by Motamayor et al (2000) [37] and Wang et al (2012) [38]. When wild-type pistils were pollinated by mutant pollen, the crossed siliques had normal seed set; however, atvdac1 siliques showed the same defective phenotype regardless of the pollen was from wild-type or mutant plants (Figure 2B, 5A; Table 1), indicating that female fertility in atvdac1 plants was affected.…”