Overexpression of 18S rRNA methyltransferase CrBUD23 enhances biomass and lutein content in Chlamydomonas reinhardtii

Chenglong Liu; Haoze Guo; Xinmei Zhao; Bingxi Zou; Ting Sun; Jinwei Feng; Zhiyong Zeng; Xueer Wen; Jun Chen; Zhangli Hu; Sulin Lou; Hui Li

doi:10.3389/fbioe.2023.1102098

Overexpression of 18S rRNA methyltransferase CrBUD23 enhances biomass and lutein content in Chlamydomonas reinhardtii

Front Bioeng Biotechnol. 2023 Feb 3:11:1102098. doi: 10.3389/fbioe.2023.1102098. eCollection 2023.

Authors

Chenglong Liu^{1

2}, Haoze Guo¹, Xinmei Zhao¹, Bingxi Zou¹, Ting Sun¹, Jinwei Feng¹, Zhiyong Zeng¹, Xueer Wen¹, Jun Chen¹, Zhangli Hu¹, Sulin Lou¹, Hui Li¹

Affiliations

¹ Guangdong Engineering Research Center for Marine Algal Biotechnology, Guangdong Provincial Key Laboratory for Plant Epigenetics, Shenzhen Key Laboratory of Marine Bioresource and Eco-Environmental Science, Longhua Innovation Institute for Biotechnology, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, China.
² College of Optoelectronic Engineering, Shenzhen University, Shenzhen, China.

Abstract

Post-transcriptional modification of nucleic acids including transfer RNA (tRNA), ribosomal RNA (rRNA) and messenger RNA (mRNA) is vital for fine-tunning of mRNA translation. Methylation is one of the most widespread post-transcriptional modifications in both eukaryotes and prokaryotes. HsWBSCR22 and ScBUD23 encodes a 18S rRNA methyltransferase that positively regulates cell growth by mediating ribosome maturation in human and yeast, respectively. However, presence and function of 18S rRNA methyltransferase in green algae are still elusive. Here, through bioinformatic analysis, we identified CrBUD23 as the human WBSCR22 homolog in genome of the green algae model organism Chlamydonomas reinhardtii. CrBUD23 was a conserved putative 18S rRNA methyltransferase widely exited in algae, plants, insects and mammalians. Transcription of CrBUD23 was upregulated by high light and down-regulated by low light, indicating its role in photosynthesis and energy metabolism. To characterize its biological function, coding sequence of CrBUD23 fused with a green fluorescence protein (GFP) tag was derived by 35S promoter and stably integrated into Chlamydomonas genome by glass bead-mediated transformation. Compared to C. reinhardtii wild type CC-5325, transgenic strains overexpressing CrBUD23 resulted in accelerated cell growth, thereby leading to elevated biomass, dry weight and protein content. Moreover, overexpression of CrBUD23 increased content of photosynthetic pigments but not elicit the activation of antioxidative enzymes, suggesting CrBUD23 favors growth and proliferation in the trade-off with stress responses. Bioinformatic analysis revealed the G1177 was the putative methylation site in 18S rRNA of C. reinhardtii CC-849. G1177 was conserved in other Chlamydonomas isolates, indicating the conserved methyltransferase activity of BUD23 proteins. In addition, CrTrm122, the homolog of BUD23 interactor Trm112, was found involved in responses to high light as same as CrBUD23. Taken together, our study revealed that cell growth, protein content and lutein accumulation of Chlamydomonas were positively regulated by the 18S rRNA methyltransferase CrBUD23, which could serve as a promising candidate for microalgae genetic engineering.

Keywords: 18S rRNA methyltransferase; Chlamydomonas reinhardtii; CrBUD23; CrTrm112; biomass; lutein; overexpression.

Grants and funding

This research was supported by the China National Key Research and Development Project (No. 2018YFA0902500), National Natural Science Foundation of China (No. 31970366) and Guangdong Natural Science Foundation (No. 2021A1515011590) and Guangdong Province Key Research and Development Project (No. 2022B1111070005) and Innovation-Driven Development Special Fund Project of Guangxi (Guike AA18242047). The funding bodies had no role in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript.