The plant cell cycle: Pre-Replication complex formation and controls

Abstract

The multiplication of cells in all living organisms requires a tight regulation of DNA replication. Several mechanisms take place to ensure that the DNA is replicated faithfully and just once per cell cycle in order to originate through mitoses two new daughter cells that contain exactly the same information from the previous one. A key control mechanism that occurs before cells enter S phase is the formation of a pre-replication complex (pre-RC) that is assembled at replication origins by the sequential association of the origin recognition complex, followed by Cdt1, Cdc6 and finally MCMs, licensing DNA to start replication. The identification of pre-RC members in all animal and plant species shows that this complex is conserved in eukaryotes and, more importantly, the differences between kingdoms might reflect their divergence in strategies on cell cycle regulation, as it must be integrated and adapted to the niche, ecosystem, and the organism peculiarities. Here, we provide an overview of the knowledge generated so far on the formation and the developmental controls of the pre-RC mechanism in plants, analyzing some particular aspects in comparison to other eukaryotes.

Cell type specific transcriptional reprogramming of maize leaves during Ustilago maydis induced tumor formation

“…In the HPT dataset we found exclusively upregulated ORC5, ORC6, CDC6, CDT1 (b), SLD5, POLE1, RFC1 and RPA1; additionally PSF1 and PCNA1, which are downregulated. In HTT we found exclusively upregulated genes including ORC2, MCM3, MCM4, MCM5, MCM7, MCM10, TOPBP1 (MEI1), POLA3, POLA4, POLD1, POLD3, RFC2, RFC3, RFC4, RPA1, RPA2 and RPA3 25,51 . POLA2 lays down a short RNA/DNA primer in the lagging strand synthesis 25 , and is upregulated in both HPT and HTT datasets.…”

“…The pre-RC is a very important part of the cell cycle as it defines the origins to initiate DNA replication, regulates DNA replication and assures that each daughter cell receives identic DNA copies 51 . Pre-RC members are conserved in all eukaryotes and previous studies have shown that plants core DNA replication machinery is more similar to vertebrates than single celled yeasts 25–27 .…”

“…Pre-RC members are conserved in all eukaryotes and previous studies have shown that plants core DNA replication machinery is more similar to vertebrates than single celled yeasts 25–27 . The pre-RC consist of an initiator to establish the site of replication initiation (ORC), a helicase to unwind DNA (MCM complex), and CDC6 and CDT1, which act synergistically to load the MCM complex 25,51 . The formation of a pre-replication complex (pre-RC) is a key control mechanism occurring before cells enter S-phase 51 .…”

“…The pre-RC consist of an initiator to establish the site of replication initiation (ORC), a helicase to unwind DNA (MCM complex), and CDC6 and CDT1, which act synergistically to load the MCM complex 25,51 . The formation of a pre-replication complex (pre-RC) is a key control mechanism occurring before cells enter S-phase 51 .…”

A Tale of Two Cycles

“…Entry into S phase, when DNA is replicated, is one of the most highly regulated events in the cell cycle. A prerequisite for DNA replication is binding of CDC6 to replication origins, which can only occur during G1, when CDK activity is at its lowest (Castellano et al, 2004;Brasil et al, 2017). However, DNA replication cannot begin until CDK levels rise at the G1/S transition, thus preventing rereplication of origins after S has begun.…”