Underexpression of the plant NOTCHLESS gene, encoding a WD-repeat protein, causes pleitropic phenotype during plant development

Abstract

WD-repeat proteins are involved in a breadth of cellular processes. While the WD-repeat protein encoding gene NOTCHLESS has been involved in the regulation of the Notch signaling pathway in Drosophila, its yeast homolog Rsa4p was shown to participate in 60S ribosomal subunit biogenesis. The plant homolog ScNLE was previously characterized in Solanum chacoense (ScNLE) as being involved in seed development. However, expression data and reduced size of ScNLE underexpressing plants suggested in addition a role during shoot development. We here report the detailed phenotypic characterization of ScNLE underexpressing plants during shoot development. ScNLE was shown to be expressed in actively dividing cells of the shoot apex. Consistent with this, ScNLE underexpression caused pleiotropic defects such as a reduction in aerial organ size, a reduction in some organ numbers, delayed flowering, and an increase in stomatal index. Analysis of adaxial epidermal cells revealed that both cell number and cell size were reduced in mature leaves of ScNLE underexpressing lines. Two-hybrid screens with the Nle domain and the WD-repeat domain of ScNLE allowed the isolation of homologs of yeast MIDASIN and NSA2 genes, the products of which are involved in 60S ribosomal subunit biogenesis in yeast. A ScNLE-GFP chimeric protein was localized in both the cytoplasm and nucleus. These data altogether suggest that ScNLE likely plays a role in 60S ribosomal subunit biogenesis, which is essential for proper cellular growth and proliferation during plant development.

The MIDASIN and NOTCHLESS genes are essential for female gametophyte development in Arabidopsis thaliana

“…Ribosome biogenesis was mostly characterized in yeast but most of the trans-acting factors identified, including MDN1/ REA1 and NLE/RSA4 (Chantha et al, 2006), are well conserved in higher eukaryotes and ribosome biogenesis pathway is therefore expected to be similar in plants, animals and fungi (Fatica and Tollervey, 2002;FromontRacine et al, 2003;Tschochner and Hurt, 2003). The Solanum chacoense MDN1 and NLE proteins were shown to interact together in two-hybrid assays, which brings support to the conservation of 60S subunit biogenesis process in plants (Chantha and Matton, 2007). In yeast, REA1 is associated with an intermediate pre-60S particle termed the Rix1-particle in the nucleoplasm.…”

“…Overall sequence identities (similarities in parenthesis) with AtMDN1 were as follows: Vitis vinifera 51 % (65 %), Populus trichocarpa 49 % (65 %), Ricinus communis 47 % (64 %), and Oryza sativa 39 % (54 %). Comparison with the 816 aa C-terminal sequence of the Solanum chacoense ScMDN1 that was shown to interact with ScNLE (Chantha and Matton 2007), revealed a similar sequence identity range, from 57 to 40 % identity (71 to 55 % similarity) with the corresponding MDN1 C-terminal region from V. vinifera, P. trichocarpa, R. communis, A. thaliana, and O. sativa. The MDN1 protein comprises two highly conserved domains: an AAA ATPase domain in its N-terminal region and a MIDAS domain at its C-terminus ( Figure 1B) (Garbarino and Gibbons, 2002).…”

“…In Saccharomyces cerevisiae, MDN1/REA1 was identified with NLE/RSA4 in the same protein complexes as non-ribosomal factors participating in 60S ribosomal subunit maturation (Bassler et al, 2001;Gavin et al, 2002;Nissan et al, 2002). The wild potato Solanum chacoense ScMDN1 ortholog was recently shown to interact with ScNLE in yeast two-hybrid assays (Chantha and Matton, 2007). Consistent with an involvement in a common cellular process, we also show that the introduction of an AtNLE-RNA interference construct in Arabidopsis also leads to a semisterility phenotype caused by defects in female gametophyte development.…”

“…Previous yeast two-hybrid screens have shown that the S. chacoense MDN1 (ScMDN1) ortholog interacts with the WD-repeat NOTCHLESS (ScNLE) protein (Chantha and Matton, 2007) and tandem affinity purification assays in yeast have isolated both proteins as components of the same pre-60S ribosomal protein complexes (Bassler et al, 2001;Gavin et al, 2002;Nissan et al, 2002). We therefore wanted to determine if the AtNLE gene acts in the same developmental pathway as the AtMDN1 gene in Arabidopsis.…”

Ribosome biogenesis dysfunction leads to p53-mediated apoptosis and goblet cell differentiation of mouse intestinal stem/progenitor cells

“…Nle acts in large ribosomal subunit in yeasts, 20,21 fungi, 36 plants 37 and mammals. 23 Contrary to Drosophila, 38 Nle loss of function does not seem to interfere with the Notch pathway in the mouse hematopoietic 23 and intestinal (this study) lineages.…”