Retention of OsNMD3 in the cytoplasm disturbs protein synthesis efficiency and affects plant development in rice.

Yanyun Shi,Yihua Zhou,Rui Li,Baocai Zhang,Yaping Gao,Zuopeng Xu,Xiangling Liu

doi:10.1093/jxb/eru150

Abstract

The ribosome is the basic machinery for translation, and biogenesis of ribosomes involves many coordinated events. However, knowledge about ribosomal dynamics in higher plants is very limited. This study chose a highly conserved trans-factor, the 60S ribosomal subunit nuclear export adaptor NMD3, to characterize the mechanism of ribosome biogenesis in the monocot plant Oryza sativa (rice). O. sativa NMD3 (OsNMD3) shares all the common motifs and shuttles between the nucleus and cytoplasm via CRM1/XPO1. A dominant negative form of OsNMD3 with a truncated nuclear localization sequence (OsNMD3(ΔNLS)) was retained in the cytoplasm, consequently interfering with the release of OsNMD3 from pre-60S particles and disturbing the assembly of ribosome subunits. Analyses of the transactivation activity and cellulose biosynthesis level revealed low protein synthesis efficiency in the transgenic plants compared with the wild-type plants. Pharmaceutical treatments demonstrated structural alterations in ribosomes in the transgenic plants. Moreover, global expression profiles of the wild-type and transgenic plants were investigated using the Illumina RNA sequencing approach. These expression profiles suggested that overexpression of OsNMD3(ΔNLS) affected ribosome biogenesis and certain basic pathways, leading to pleiotropic abnormalities in plant growth. Taken together, these results strongly suggest that OsNMD3 is important for ribosome assembly and the maintenance of normal protein synthesis efficiency.

Highlights

The ribosome, an apparatus for translation, is universally composed of one large and one small subunit
Global expression profiles of the wild-type and transgenic plants were investigated using the Illumina RNA sequencing approach. These expression profiles suggested that overexpression of OsNMD3ΔNLS affected ribosome biogenesis and certain basic pathways, leading to pleiotropic abnormalities in plant growth. These results strongly suggest that O. sativa NMD3 (OsNMD3) is important for ribosome assembly and the maintenance of normal protein synthesis efficiency
OsNMD3 was clustered with sorghum NMD3 (SbNMD3) into a monophyletic clade that arose before the divergence of monocot and dicot phyla

Summary

Introduction

The ribosome, an apparatus for translation, is universally composed of one large and one small subunit. The large (50S) and small (30S) subunits contain three rRNAs (23S and 5S in the 50S subunit and 16S in the 30S subunit) and tens of ribosomal proteins (RPs), whereas eukaryotic large (60S) and small (40S) subunits are assembled by rRNAs of different sizes (25S, 5.8S, and 5S for the 60S subunit and 18S rRNA for the 40S subunit) and a different number of RPs (Trapman et al, 1975; Shajani et al, 2011) Both subunits have distinct functions: the small subunit is responsible for decoding genetic information, whereas the large subunit is required for polypeptide synthesis (Steitz, 2008; Schmeing and Ramakrishnan, 2009). In addition to pre-rRNA processing, folding, and interaction with ribosomal proteins, eukaryotic ribosome biogenesis requires the involvement of more than 200 nonribosomal factors The functions of these trans-acting factors include modification, intracellular transport, and energy production (Kressler et al, 2010; Panse and Johnson, 2010), and some of these roles are highly conserved in eukaryotic organisms

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Conclusion