OsORC3 is required for lateral root development in rice

Abstract

SUMMARYThe origin recognition complex (ORC) is a pivotal element in DNA replication, heterochromatin assembly, checkpoint regulation and chromosome assembly. Although the functions of the ORC have been determined in yeast and model animals, they remain largely unknown in the plant kingdom. In this study, Oryza sativa Origin Recognition Complex subunit 3 (OsORC3) was cloned using map-based cloning procedures, and functionally characterized using a rice (Oryza sativa) orc3 mutant. The mutant showed a temperaturedependent defect in lateral root (LR) development. Map-based cloning showed that a G?A mutation in the 9th exon of OsORC3 was responsible for the mutant phenotype. OsORC3 was strongly expressed in regions of active cell proliferation, including the primary root tip, stem base, lateral root primordium, emerged lateral root primordium, lateral root tip, young shoot, anther and ovary. OsORC3 knockdown plants lacked lateral roots and had a dwarf phenotype. The root meristematic zone of ORC3 knockdown plants exhibited increased cell death and reduced vital activity compared to the wild-type. CYCB1;1::GUS activity and methylene blue staining showed that lateral root primordia initiated normally in the orc3 mutant, but stopped growing before formation of the stele and ground tissue. Our results indicate that OsORC3 plays a crucial role in the emergence of lateral root primordia.

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

“…Consistent with a role in DNA replication, mRNAs of ORCs from A. thaliana , rice and maize, as well as transcripts of AtCDC6 , AtMCMs and ZmMCMs are abundant in proliferating tissues, such as root tips, lateral root development, seedlings, young leaves and flower buds (Sabelli et al , 1996; Springer et al , 2000; Castellano et al , 2001; Bastida and Puigdomenech, 2002; Masuda et al , 2004; Diaz-Trivino et al , 2005; Schreiber et al , 2006; Dang et al , 2011; Chen et al , 2013). In rice, OsORC1 and OsORC2 are strongly expressed in roots and inflorescence meristems, respectively, but there is a reduction of expression of OsORCs in tissues with low proliferative rates, leading to complete absence in mature leaves (Kimura et al , 2000; Li et al , 2005).…”

“…Complete knockout plants for ORC genes cannot survive, indicating that these genes are vital for the plant to complete its life cycle (Collinge et al , 2004; Sanchez and Gutierrez, 2009; Chen et al , 2013). Constitutive expression of a specific mutation in the PHD domain of ORC1b in A. thaliana leads to the loss of the ORC1b overexpression phenotype characterized by increased cell proliferation (Sanchez and Gutierrez, 2009), revealing that PHD is essential for ORC function in DNA replication.…”

“…In a developmental context, OsORC3 knockdown rice plants lack lateral roots and have a dwarf phenotype (Chen et al , 2013). A very fast differentiation of lateral root cells requires rapid cycles of cell division for tissue maintenance and development.…”

“…A very fast differentiation of lateral root cells requires rapid cycles of cell division for tissue maintenance and development. However, in cells with lower OsORC3 availability, the G1/S phase is compromised, leading to lower proliferation levels and tissue defects (Chen et al , 2013). …”

OsSPL3, an SBP-Domain Protein, Regulates Crown Root Development in Rice

“…The arl1 mutant line S2409 (named according to its original line number) was identified from a screen of an EMS-mutated mutant library in the japonica rice cv Shi Shou Bai Mao background. The phenotypic characterization of the wild-type and mutant plants was performed in a growth chamber at 30°C/22°C (day/night) and 60% to 70% humidity, bulb type light with a photon density of ;300 mmol m -2 s -1 , and a photoperiod of 14 h. For the hydroponically grown plants, the seedlings were grown in fullstrength Kimura nutrient solution as described previously (Chen et al, 2013). Nicotiana benthamiana plants were cultivated in growth chambers, as described previously (Lv et al, 2014).…”