Developmental and cell cycle regulation of alfalfa nucMs1, a plant homolog of the yeast Nsr1 and mammalian nucleolin.

Abstract

We report here the isolation and characterization of the nucMs1 alfalfa cDNA, whose predicted amino acid sequence structurally resembles the yeast Nsr1 protein and animal nucleolins. These proteins consist of an N-terminal acidic domain, centrally located RNA recognition motifs (RRMs), and a C-terminal glycine- and arginine-rich domain. In comparison with animal nucleolins that contain four RRMs, NucMs1 more closely resembles the yeast Nsr1 protein, which contains only two RRMs. A NucMs1 C-terminal peptide antibody specifically recognized a 95-kD nucleolar protein in alfalfa cells that changed its localization in a cell cycle-dependent manner. The nucMs1 transcript and p95nucMs1 protein levels correlated with cell proliferation, and nucMs1 gene expression was found to be induced in the G1 phase upon mitogenic stimulation of G0-arrested leaf cells. In situ hybridization analysis of different alfalfa organs during various developmental stages showed that nucMs1 gene expression is highest in root meristematic cells, but it is also found in other meristematic cells of the plant body. nucMs1 expression is tightly linked to cell proliferation but does not depend on a particular cell cycle phase. No nucMs1 expression was observed in cells that had exited the cell cycle and were undergoing differentiation or polar growth, indicating that nucMs1 may not be necessary for processes other than cell proliferation.

The nucleolar structure and the activity of NopA100, a nucleolin-like protein, during the cell cycle in proliferating plant cells

“…In fact, western blotting experiments with homologous antibodies identify one single band for nucleolin in chicken (Maridor et al 1990), fission yeast (Le´ger-Silvestre et al 1997), and peas (Tong et al 1997). Two bands are detected in proliferating alfalfa cells (Bo¨gre et al 1996), and 2-3 bands appear in Xenopus laevis (Caizergues-Ferrer et al 1989). Only in different lines of mammalian cells, as well as in the case reported here for proliferating onion cells, is a ''ladder-shaped'' pattern revealed by western blotting, which is affected by a treatment with a protease inhibitor, and can thus be interpreted as corresponding to a physiological proteolytic process.…”

“…In alfalfa, the nucleolin gene is not expressed in mitotic-arrested cells, but, upon mitogenic stimulation and cell-cycle re-entry, the gene is induced very early, exactly at the same time as a marker cyclin gene, indicating that nucleolin gene expression and cyclin expression could be regulated by the same factors. Apart from this, the expression of nucleolin is restricted to proliferating tissues of the plant (Bo¨gre et al 1996). In peas, the expression of nucleolin is regulated by light, following a close correlation with the effects of light in increasing cell proliferation and mitotic activity (Reichler et al 2001).…”

Nucleolonema as a fundamental substructure of the nucleolus

“…Actually, it has been found to be associated with the RNA precursor (Herrera and Olson 1986;Ghisolfi-Nieto et al 1996;Serin et al 1996). The expression of nucleolin and rRNA seems well coordinated (Bogre et al 1996;Tong et al 1997). Nucleolin first interacts with rRNA and recruits other factors such as U3 snoRNA to form a processing complex (Ginisty et al 1998).…”

A rice (Oryza sativa L.) MAP kinase gene, OsMAPK44, is involved in response to abiotic stresses

“…In plants, a variety of MAPKs have been identified from different plant species (Mizoguchi et al, 1994;Decroocq-Ferrant et al, 1995;Bo¨gre et al, 1996;Ligterink et al, 1997;Zhang et al, 1998). Considering the homologous MAPKs present in many organisms, it is likely that the plant MAPKs play crucial roles in plant growth and development.…”