Ribosomal protein L18aB is required for both male gametophyte function and embryo development in Arabidopsis.

Hailong Yan,Xiongbo Peng,Jing Zhao,Yang Sun,Mengxiang Sun,Yifan Wang,Dan Chen

doi:10.1038/srep31195

Abstract

Ribosomal proteins are involved in numerous essential cell activities in plants. However, the regulatory role in specific plant developmental processes has not yet been fully elucidated. Here we identified the new ribosomal protein L18aB, which is specifically involved in sexual reproduction and plays a critical role in male gametophyte development and embryo pattern formation. In rpl18aB mutant plants, the mature pollen grains can germinate normally, but their competitiveness for growing in the style is significantly reduced. More interestingly, RPL18aB is required in early embryogenesis. rpl18aB embryos displayed irregular cell division orientations in the early pro-embryo and arrested at the globular stage with possible, secondary pattern formation defects. Further investigations revealed that the polar transportation of auxin is disturbed in the rpl18aB mutant embryos, which may explain the observed failure in embryo pattern formation. The cell type-specific complementation of RPL18aB in rpl18aB was not able to recover the phenotype, indicating that RPL18aB may play an essential role in early cell fate determination. This work unravels a novel role in embryo development for a ribosomal protein, and provides insight into regulatory mechanism of early embryogenesis.

Highlights

In plants, ribosomal proteins are encoded by small gene families
To screen genes required for embryo development in Arabidopsis thaliana, we established a T-DNA insertion mutant library that contains one insertion site in the genomic DNA of qrt[1] plant background[16,17]
AS1::AS1-GFP was not expressed in the globular embryo but expressed in heart-shaped embryos, while there was no AS1::AS1-GFP expression in rpl18aB-1/rpl18aB-1 embryos (Fig. 5A–C). These results further indicated that the rpl18aB-1/ rpl18aB-1 embryos were arrested at the globular stage and never underwent the transition stage for apical-basal pattern formation

Summary

Introduction

Ribosomal proteins are encoded by small gene families. The Arabidopsis thaliana genome encodes for approximately 80 cytoplasmic ribosomal proteins, and each protein is encoded by 2–7 family members since different genes within a family share 65–100% amino acid sequence identity[1]. It was recently demonstrated that ribosomal proteins control auxin mediated developmental programs by translational regulation of auxin response factors[10] Together these findings indicate that the specific role of each ribosomal protein in plant development must be studied individually, despite their general function being well known. Mutations in seven cytoplasmic ribosomal proteins, S6, S11, L2, L8, L23, L19 L40 and RPL27a, resulted in embryo developmental defects[14,15] In these mutants, the earliest divisions of the zygote forming a suspensor and a globular stage embryo appear to be unaltered, indicating that early patterning events are unaffected by the loss of these ribosomal proteins. The Loss of function of this gene result in weakened function of male gametophyte and abortion of early embryo development, with a striking alteration in early embryo patterning, indicating the essential role of RPL18aB in these developmental processes

Methods

Results

Conclusion