Key Laboratory of South China Agricultural Plant Molecular Analysis and Gene Improvement, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
BMC Genomics. 2021 Nov 8;22(1):806. doi: 10.1186/s12864-021-08087-y.
Paphiopedilum, commonly known as slipper orchid, is an important genus of orchid family with prominent horticultural value. Compared with conventional methods such as tillers and in vitro shoots multiplication, induction and regeneration of protocorm-like bodies (PLBs) is an effective micropropagation method in Paphiopedilum. The PLB initiation efficiency varies among species, hybrids and varieties, which leads to only a few Paphiopedilum species can be large-scale propagated through PLBs. So far, little is known about the mechanisms behind the initiation and maintenance of PLB in Paphiopedilum.
A protocol to induce PLB development from seed-derived protocorms of Paphiopedilum SCBG Huihuang90 (P. SCBG Prince × P. SCBG Miracle) was established. The morphological characterization of four key PLB developmental stages showed that significant polarity and cell size gradients were observed within each PLB. The endogenous hormone level was evaluated. The increase in the levels of indoleacetic acid (IAA) and jasmonic acid (JA) accompanying the PLBs differentiation, suggesting auxin and JA levels were correlated with PLB development. Gibberellic acid (GA) decreased to a very low level, indicated that GA inactivation may be necessary for shoot apical meristem (SAM) development. Comparative transcriptomic profiles of four different developmental stages of P. SCBG Huihuang90 PLBs explore key genes involved in PLB development. The numbers of differentially expressed genes (DEGs) in three pairwise comparisons (A vs B, B vs C, C vs D) were 1455, 349, and 3529, respectively. KEGG enrichment analysis revealed that DEGs were implicated in secondary metabolite metabolism and photosynthesis. DEGs related to hormone metabolism and signaling, somatic embryogenesis, shoot development and photosynthesis were discussed in detail.
This study is the first report on PLB development in Paphiopedilum using transcriptome sequencing, which provides useful information to understand the mechanisms of PLB development.
兜兰，俗称拖鞋兰，是兰科的一个重要属，具有突出的园艺价值。与分株和体外芽增殖等常规方法相比，原球茎状体（PLB）的诱导和再生是兜兰有效的微繁殖方法。PLB 的诱导效率因物种、杂种和品种而异，这导致只有少数兜兰物种可以通过 PLB 进行大规模繁殖。到目前为止，关于兜兰 PLB 起始和维持的机制知之甚少。
建立了从兜兰 SCBG Huihuang90（P. SCBG Prince × P. SCBG Miracle）种子来源的原球茎中诱导 PLB 发育的方案。对四个关键 PLB 发育阶段的形态特征进行了描述，结果表明每个 PLB 内存在明显的极性和细胞大小梯度。评估了内源激素水平。随着 PLB 分化，生长素（IAA）和茉莉酸（JA）水平的增加表明生长素和 JA 水平与 PLB 发育相关。赤霉素（GA）水平降低到非常低的水平，表明 GA 失活可能是芽顶分生组织（SAM）发育所必需的。对兜兰 SCBG Huihuang90 的四个不同发育阶段的 PLB 进行比较转录组分析，探讨了参与 PLB 发育的关键基因。在三个两两比较（A 与 B、B 与 C、C 与 D）中，差异表达基因（DEGs）的数量分别为 1455、349 和 3529。KEGG 富集分析表明，DEGs 与次生代谢物代谢和光合作用有关。详细讨论了与激素代谢和信号转导、体细胞胚胎发生、芽发育和光合作用相关的 DEGs。
这是首次使用转录组测序研究兜兰 PLB 发育的报告，为理解 PLB 发育机制提供了有用信息。
