WSL5, a pentatricopeptide repeat protein, is essential for chloroplast biogenesis in rice under cold stress

Abstract

Abstact 23Chloroplasts play an essential role in plant growth and development, and cold has a great effect 24 on chloroplast development. Although many genes or regulators involved in chloroplast 25 biogenesis and development have been isolated and characterized, identification of novel 26 components associated with cold is still lacking. In this study, we reported the functional 27 characterization of white stripe leaf 5 (wsl5) mutant in rice. The mutant developed white-striped 28 leaves during early leaf development and was albinic when planted under cold stress. Genetic and 29 molecular analysis revealed that WSL5 encodes a novel chloroplast-targeted pentatricopeptide 30 repeat protein. RNA-seq analysis showed that expression of nuclear-encoded photosynthetic 31 genes in the mutant was significantly repressed, and expression of many chloroplast-encoded 32 genes was also significantly changed. Notably, the WSL5 mutation caused defects in editing of 33 rpl2 and atpA, and in splicing of rpl2 and rps12. Chloroplast ribosome biogenesis was impaired 34 under cold stress. We propose that WSL5 is required for normal chloroplast development in rice 35 under cold stress. 36 37Key words: chloroplast biogenesis, cold stress, Oryza sativa, RNA-seq, RNA splicing, WSL5. 38 39 All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/239905 doi: bioRxiv preprint first posted online Dec. 26, 2017; Introduction 40Cold is an important environmental factor affecting chloroplast development and growth in juvenile 41 plants and sudden low-temperature periods that often occur during early seedling development in 42 spring can directly affect production (Kusumi and Iba, 2014). Rice seedlings are susceptible to cold 43 stress with an impact that ultimately affects grain yield (Liu et al. 2013). Therefore, cold stress is a 44 common problem that affects grain production, and rice varieties with increased cold tolerance are 45 preferred (Zhao et al. 2017). Many studies have suggested that plants can regulate early chloroplast 46 development under cold stress. In certain virescent mutants the chlorophyll content in young leaves is 47 low, but gradually increases to normal levels as they develop (Yoo et al. 2009). Temperature-sensitive 48 virescent mutants were used to study mechanisms regulating chloroplast development in seedlings 49 under cold stress conditions, and many genes were identified, such as V3, St1, OsV4, TCD9 and TSV 50 (Yoo et al. 2009; Gong et al. 2014; Jiang et al. 2014; Sun et al. 2017). However, the mechanisms of 51 chloroplast development in rice seedlings under cold stress remain poorly understood. 52Chloroplasts are essential for photosynthesis and have crucial roles in plant development and growth 53 by fixation of CO 2 and biosynthesis of carbon skeletons as well as other physiological processes (Jarvis 54and López-Juez...