Molecular cloning, genomic organization and functional analysis of the ribosomal protein L4/L1 (RPL4) gene from Arachis hypogaea

Abstract

Wu, Q., Wang, X. Z., Tang, Y. Y., Yu, H. T., Cui, F. G., Zhang, J. C. and Wang, C. T. 2014. Molecular cloning, genomic organization and functional analysis of the ribosomal protein L4/L1 (RPL4) gene from Arachis hypogaea. Can. J. Plant Sci. 94: 85–97. The ribosomal proteins have been shown to be important in plant polarity establishment, cell proliferation, leaf shape and auxin-related development. The RPL4 protein is crucial for the maintenance of ribosomal translational efficiency and fidelity. This study concerns the RPL4 gene from Arachis hypogaea. The full-length cDNA (1538 bp) of RPL4 consisted of an open-reading frame of 1221 bp encoding 406 amino acids. The genomic DNA sequence of RPL4 gene consisted of 1491 bp containing two exons and one 270-bp intron. The RPL4 mRNA transcript was mainly expressed in roots and leaves, and fewer signals were detected in stems. The sequence data revealed that RPL4 encoded a typical ribosomal protein L4/L1e domain. Phylogenetic analysis for genes encoding proteins showed that RPL4 were conserved within dicotyledonous and monocotyledonous plants. The ratios of nonsynonymous/synonymous substitution rate (ω=d N/d S) were analyzed. No sites were identified under positive selection. In the whole RPL4 sequence, d S greatly exceeded d N in all branches of the tree (d N/d S<< 1.0), indicating that functional constraints (purifying selection) have acted on RPL4 throughout evolution. The differences among plants and animals and Caenorhabditis elegans may indicate functional differentiation during species evolution.