Flower transcriptome dynamics during nectary development in pepper (Capsicum annuum L.)

Abstract The measurement of gene expression can provide important information about gene function and the molecular basis for developmental processes. We analyzed the transcriptomes at three different developmental stages of pepper flower [sporogenous cell division, stage (B1); pollen mother cell meiosis, stage (B2); and open flower (B3)]. In the cDNA libraries for B1, B2, and B3: 82718, 77061, and 91491 unigenes were assembled, respectively. A total of 34,445 unigene sequences and 128 pathways were annotated by KEGG pathway analysis. Several genes associated with nectar biosynthesis and nectary development were identified, and 8,955, 12,182, and 23,667 DEGs were identified in the B2 vs B1, B3 vs B1, and B3 vs. B2 comparisons. DEGs were involved in various metabolic processes, including flower development, nectar biosynthesis, and nectary development. According to the RNA-seq data, all 13 selected DEGs showed similar expression patterns after q-PCR analysis. Sucrose-phosphatase, galactinol-sucrose galactosyltransferase, and sucrose synthase played very important roles in nectar biosynthesis, and CRABS CLAW could potentially be involved in mediating nectary development. A significant number of simple sequence repeat and single nucleotide polymorphism markers were predicted in the Capsicum annuum sequences. The new results provide valuable genetic information about flower development in pepper.

摘要 基因表达检测可为解析基因功能及发育进程的分子基础提供关键信息。本研究针对辣椒花的三个不同发育阶段开展转录组分析：造孢细胞分裂期（B1阶段）、花粉母细胞减数分裂期（B2阶段）以及盛开花朵期（B3阶段）。针对B1、B2、B3的cDNA文库，分别组装得到82718、77061及91491个单基因（unigene）。通过京都基因与基因组百科全书（KEGG）通路分析，共注释到34445条单基因序列及128条代谢通路。本研究鉴定出多个与花蜜生物合成及蜜腺发育相关的基因；在B2与B1、B3与B1及B3与B2的组间比较中，分别鉴定出8955、12182及23667个差异表达基因（Differentially Expressed Genes, DEGs）。这些差异表达基因参与多种代谢过程，包括花发育、花蜜生物合成及蜜腺发育。基于RNA-seq测序数据，随机选取的13个差异表达基因经实时定量PCR（quantitative real-time PCR, q-PCR）验证后，其表达模式与测序结果高度一致。其中，蔗糖磷酸酶、半乳糖肌醇蔗糖半乳糖基转移酶及蔗糖合酶在花蜜生物合成中发挥至关重要的作用，而CRABS CLAW基因可能参与调控蜜腺发育。本研究在辣椒（Capsicum annuum）序列中预测得到大量简单序列重复（simple sequence repeat, SSR）及单核苷酸多态性（single nucleotide polymorphism, SNP）分子标记。上述研究结果为解析辣椒花发育的遗传机制提供了极具价值的遗传数据资源。