Fujian Engineering Research Center for Characteristic Floriculture,Institute of Crop Sciences(Fujian Germplasm Resources Center),Fujian Academy of Agricultural Sciences,Fuzhou,Fujian 350013,China
Objective Analyze the molecular mechanism of leaf color variation in C.ensifolium,to establish a theoretical foundation for molecular breeding of its leaf variegation. Method In this study,the green leaf margins of C.ensifolium ‘Xiaotaohong’ and the white leaf margins of its mutant ‘JQ’ were used as materials,and photosynthetic pigment content measurement,chloroplast ultrastructure observation,as well as comparative proteomic and transcriptomic analyses were conducted. Result ①The contents of chlorophyll a,chlorophyll b,and carotenoids,as well as the chlorophyll a/b ratio in ‘JQ’ were significantly lower than those in ‘Xiaotaohong’.② The mesophyll cells of ‘JQ’ contained few or no chloroplasts.The few existing chloroplasts were swollen,with nearly vanished internal structures,numerous unstacked single thylakoids,and abundant osmiophilic granules.③A total of 1 962 differentially expressed genes (DEGs) were detected,including 717 upregulated and 1 245 downregulated.In addition,895 differentially abundant proteins (DAPs) were identified,comprising 523 in low abundance and 372 in high abundance.④ The enrichment analysis of the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway revealed that the identified DEGs and DAPs were mainly related to photosynthesis antennas and photosynthesis.A comparative analysis between ‘Xiaotaohong’and ‘JQ’ identified eight DEGs/DAPs involved in photosynthesis antennas and photosynthesis. Conclusion Transcriptional alterations,post-transcriptional regulation,and translational changes of key enzymes involved in photosynthesis and photosynthetic pigment metabolism may play crucial roles in leaf color muttion of C.ensifolium.
原始读数(raw reads)最初通过Illumina测序产生。通过删除低质量序列(reads),获得过滤后高质量序列(reads)。将高质量序列(reads)扩展到具有重叠区域的较长重叠群(contigs)中,然后进一步组装成转录本(transcripts),最后聚集成单基因(unigenes)。基于序列相似性,将所有组装的单基因与公共数据库进行比较(E-value cut-off at 10-5)。装配及功能注释参照Ye等[25]的方法。
用Bowtie 2将修剪后的序列(reads)与组装的转录组进行比较[27],用RSEM(RNA-seq by expectation maximization) 评估表达水平[28]。应用FPKM (fragments per kilobase of transcript per million mapped reads)计算单基因(unigenes)的表达丰度[29]。用DESeq分析不同文库中的差异表达基因(DEGs)[30],将P<0.01和log2(FC(fold change))>2作为筛选DEGs的阈值。
为了验证转录组和蛋白质组分析结果,对几个关键基因进行了RT-qPCR。结果(图8)显示,Lhca2、Lhca1、Lhcb1-1、Lhcb3、Lhcb2、PsbO、PsbS和PsbA等8个基因的RT-qPCR表达趋势与转录组和蛋白质组表达趋势相似;在转录组和蛋白质组中表达趋势不同的9个基因中,有6个基因(Lhcb4、Lhcb5、Lhcb1-2、Lhca3、PsaD、F-type ATP ase b)的RT-qPCR表达趋势与蛋白质组表达趋势相似,有3个基因(Lhca4、Lhcb6、CCD)的RT-qPCR表达趋势与转录组相同。
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