Arabidopsis replication factor C4 is critical for DNA replication during the mitotic cell cycle

Abstract

Replication factor C (RFC) is a conserved eukaryotic complex consisting of RFC1/2/3/4/5. It plays important roles in DNA replication and the cell cycle in yeast and fruit fly. However, it is not very clear how RFC subunits function in higher plants, except for the Arabidopsis (At) subunits AtRFC1 and AtRFC3. In this study, we investigated the functions of AtRFC4 and found that loss of function of AtRFC4 led to an early sporophyte lethality that initiated as early as the elongated zygote stage, all defective embryos arrested at the two- to four-cell embryo proper stage, and the endosperm possessed six to eight free nuclei. Complementation of rfc4-1/+ with AtRFC4 expression driven through the embryo-specific DD45pro and ABI3pro or the endosperm-specific FIS2pro could not completely restore the defective embryo or endosperm, whereas a combination of these three promoters in rfc4-1/+ enabled the aborted ovules to develop into viable seeds. This suggests that AtRFC4 functions simultaneously in endosperm and embryo and that the proliferation of endosperm is critical for embryo maturation. Assays of DNA content in rfc4-1/+ verified that DNA replication was disrupted in endosperm and embryo, resulting in blocked mitosis. Moreover, we observed a decreased proportion of late S-phase and M-phase cells in the rfc4-1/- seedlings, suggesting that incomplete DNA replication triggered cell cycle arrest in cells of the root apical meristem. Therefore, we conclude that AtRFC4 is a crucial gene for DNA replication.

Subunit Interaction Differences Between the Replication Factor C Complexes in Arabidopsis and Rice

“…Though no developmental defects were observed in heterozygous plants of the mutants during vegetative growth, their mature siliques contained white abnormal ovules at a frequency of about 25% (Figure 2B ; Table 1 ). All of these results showed that the mutations in AtRFC2/3/5 were lethal in homozygous progenies, similar to the mutant rfc4 (Qian et al, 2018 ).…”

“…In Arabidopsis , the expression and function of RFC1 and RFC4 have been reported (Liu et al, 2013 ; Qian et al, 2018 ). To assess the functions of AtRFC2/3/5 , we first detected their expressions in various Arabidopsis tissues using quantitative real-time PCR (qRT-PCR) assays.…”

“…AtRFC3 plays a crucial role in systemic acquired resistance, cell proliferation and DNA replication (Xia et al, 2009 , 2010 ). AtRFC4 is crucial for DNA replication (Qian et al, 2018 ). In this study, we found that the rfc2-1, rfc3-2 , and rfc5-1 of the T-DNA insertion lines caused seed lethality (Figure 2A ).…”

“…Noco2, suggesting that AtRFC3 negatively regulates systemic acquired resistance and has crucial functions in cell proliferation and DNA replication (Xia et al, 2009 , 2010 ). Mutation of AtRFC4 had severe defects in DNA replication and led to seed abortion and seedling lethality, indicating that AtRFC4 is crucial for DNA replication (Qian et al, 2018 ).…”

Interactional similarities and differences in the protein complex of PCNA and DNA replication factor C between rice and Arabidopsis

“…Other studies have shown that AtRFC1 also participates in meiotic homologous recombination [18, 19]. AtRFC3 is involved in negative regulation of systemic acquired resistance, and AtRFC4 is critical for DNA replication during the mitotic cell cycle [20, 21].…”