Abstract
BackgroundChloroplasts are essential for photosynthesis and play key roles in plant development. High temperature affects structure of chloroplasts and metabolism in plants. The seryl-tRNA synthetase plays an important role in translation of proteins. Although seryl-tRNA synthetase has been widely studied in microbes and animals, few studies have reported about its role in chloroplast development under high temperature in rice.ResultsIn this study, we isolated a novel temperature-sensitive chlorophyll-deficient 11 (tscd11) mutant by ethyl methane sulfonate (EMS) mutagenesis of japonica variety Wuyujing7. The tscd11 mutant developed albino leaves at the 3-leaf stage under high temperature (35 °C), but had normal green leaves under low temperature (25 °C). Consistent with the albino phenotype, impaired chloroplasts, decreased chlorophyll content and increased ROS accumulation were found in the tscd11 mutant at 35 °C. Fine mapping and DNA sequencing of tscd11 revealed a missense mutation (G to A) in the eighth exon of LOC_Os11g39670 resulted in amino acid change (Glu374 to Lys374). The TSCD11 gene encodes a seryl-tRNA synthetase localized to chloroplast. Complementation test confirmed that the point mutation in TSCD11 is responsible for the phenotype of tscd11. TSCD11 is highly expressed in leaves. Compared with the wild type (WT), mutation in TSCD11 led to significant alteration in expression levels of genes associated with chlorophyll biosynthesis, photosynthesis and chloroplast development under high temperature.ConclusionsTSCD11, encoding a seryl-tRNA synthetase localized to chloroplast, is vital to early chloroplast development at high temperature in rice, which help to further study on the molecular mechanism of chloroplast development under high temperature.
Highlights
ResultsPhenotypes of the tscd11 Mutant in Different Environmental Temperatures At the seedling stage, the tscd11 mutant plants exhibited different phenotypes with different sowing date in the paddy field
Some genes have been cloned in rice so far including Mg-chelatase H subunit (OsCHLH), Virescent 1 (V1), Chlorophyll a Oxygenase (OsCAO1), Yellow Leaf and Early Flowering (YE1), Heat-stress Sensitive Albino 1 (HSA1), Virescent 2 (V2), Yellow-green Leaf 1 (YGL1), Virescent 3 (V3), Stripe1 (ST1) and Thermo-sensitive Chlorophyll-deficient Mutant 5 (TCM5) (Jung et al 2003; Kusumi et al 2011; Lee et al 2005; Peng et al 2019; Qiu et al 2017; Sugimoto et al 2007; Wu et al 2007; Yoo et al 2009; Zheng et al 2016)
When the tscd11 mutant plants were sown in May, they developed white-striped leaves, and their contents of chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoid (Car) were decreased by 23.2%, 34.6% and 14.8% compared to the wild-type plants, respectively (Fig. 1a, c)
Summary
ResultsPhenotypes of the tscd Mutant in Different Environmental Temperatures At the seedling stage, the tscd mutant plants exhibited different phenotypes with different sowing date in the paddy field. When the tscd mutant plants were sown in May, they developed white-striped leaves, and their contents of chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoid (Car) were decreased by 23.2%, 34.6% and 14.8% compared to the wild-type plants, respectively (Fig. 1a, c). The new third leaf of the tscd mutant showed albino phenotype when shifted from 25 °C to 35 °C at the 3-leaf stage, and the contents of Chl a, Chl b and Car in tscd were only 9.5%, 16.9% and 20.6% that of the WT, respectively (Additional file 1: Fig. S1f, j). Differences in pigment contents became smaller in the paddy field as climate temperature decreased from summer till fall (Additional file 1: Fig. S2) in Hangzhou of China These results illustrate that the tscd mutant is sensitive to high temperature. Minority of them are high temperature sensitive, including HSA1 and TCM5, which are considered to be ideal materials for studying the mechanisms underlie the response to heat stress during chloroplast development
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