Arabidopsis paralogous genes RPL23aA and RPL23aB encode functionally equivalent proteins

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RESEARCH ARTICLE

Open Access

Arabidopsis paralogous genes RPL23aA and RPL23aB encode functionally equivalent proteins Wei Xiong1,2, Xiangze Chen1, Chengxin Zhu1, Jiancong Zhang1, Ting Lan1,2, Lin Liu1, Beixin Mo1* Xuemei Chen3*

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Abstract Background: In plants, each ribosomal protein (RP) is encoded by a small gene family but it is largely unknown whether the family members are functionally diversified. There are two RPL23a paralogous genes (RPL23aA and RPL23aB) encoding cytoplasmic ribosomal proteins in Arabidopsis thaliana. Knock-down of RPL23aA using RNAi impeded growth and led to morphological abnormalities, whereas knock-out of RPL23aB had no observable phenotype, thus these two RPL23a paralogous proteins have been used as examples of ribosomal protein paralogues with functional divergence in many published papers. Results: In this study, we characterized T-DNA insertion mutants of RPL23aA and RPL23aB. A rare non-allelic noncomplementation phenomenon was found in the F1 progeny of the rpl23aa X rpl23ab cross, which revealed a dosage effect of these two genes. Both RPL23aA and RPL23aB were found to be expressed almost in all examined tissues as revealed by GUS reporter analysis. Expression of RPL23aB driven by the RPL23aA promoter can rescue the phenotype of rpl23aa, indicating these two proteins are actually equivalent in function. Interestingly, based on the publicly available RNA-seq data, we found that these two RPL23a paralogues were expressed in a concerted manner and the expression level of RPL23aA was much higher than that of RPL23aB at different developmental stages and in different tissues. Conclusions: Our findings suggest that the two RPL23a paralogous proteins are functionally equivalent but the two genes are not. RPL23aA plays a predominant role due to its higher expression levels. RPL23aB plays a lesser role due to its lower expression. The presence of paralogous genes for the RPL23a protein in plants might be necessary to maintain its adequate dosage. Keywords: Ribosome, Ribosomal protein, RPL23a, Gene dosage, Paralogue, Functional specialization

* Correspondence: [email protected]; [email protected] 1 Guangdong Provincial Key Laboratory for Plant Epigenetics, Longhua Bioindustry and Innovation Research Institute, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, Guangdong, China 3 Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons