离体百合鳞茎发育及淀粉合成酶基因LohGBSSI的克隆与表达

  目的  淀粉是百合Lilium spp.鳞茎的主要组成成分，淀粉代谢对于百合鳞茎发育至关重要，对其开展深入研究有助于解决鳞茎繁育慢等产业化难题。  方法  以主栽品种东方百合‘索邦’Lilium ‘Sorbonne’离体鳞茎为材料，在观测不同发育时期形态和淀粉积累的基础上，利用cDNA末端快速扩增技术（RACE），克隆淀粉合成代谢关键酶颗粒结合型淀粉合成酶基因LohGBSSI，并对其开展不同组织及发育期基因表达谱分析。  结果  ① 根据形态及源-库转换，离体百合鳞茎形成和发育过程可分为小鳞茎膨大初期（0~15 d），小鳞茎快速膨大期（15~55 d）及小鳞茎膨大后期（55~75 d）。②‘索邦’颗粒结合型淀粉合成酶基因LohGBSSI（GenBank登录号:MF101407.1）全长1 913 bp，开放阅读框（ORF）长为1 665 bp，编码554个氨基酸。氨基酸序列与兰州百合Lilium davidii var.unicolor GBSSI同源性较高（92%），推测该基因可能属于GBSSI基因家族。③LohGBSSI基因在鳞茎和叶中表达显著高于茎段和根，表明直链淀粉合成的最主要部位为源-库关键器官；不同发育时期鳞茎内LohGBSSI的表达在15 d时最高，暗示鳞茎形成初期需淀粉快速合成以便形态建成。  结论  为后续解析淀粉合成关键酶基因GBSS在鳞茎发育中的功能奠定了基础，也为百合进行淀粉相关基因修饰提供了依据。

In vitro bulblet development and analysis of starch synthase gene(LohGBSSI) from Lilium 'Sorbonne'

  Objective  To promote the breeding speed of Lilium spp. bulbs, a study is conducted of the metabolism of starch, a major component of lily bulbs.  Method  Taking the bulbs in vitro of oriental hybrids Lilium 'Sorbonne', the most popular variety as the research subject, observations are made of the morphological changes and starch accumulation during different development stages. Thereafter, the granule bound starch synthase gene LohGBSSI was cloned with RACE employed, and the gene expression profiles of different tissues and development stages were analyzed.  Result  (1) During the formation and development process of lily bulblets cultured in vitro, in terms of the morphological traits and source-sink transition, there are mainly three stages namely the initial swelling stage, the rapid swelling stage and later swelling stage. (2) The total length of LohGBSSI (GenBank accession number:MF101407.1) is 1 913 bp, and the open reading frame is 1 665 bp, encoding 554 amino acids, which was highly homologous to GBSSI of Lilium davidii var. unicolor (92%), suggesting that this gene might belong with the GBSSI gene family. (3) The expression of LohGBSSI gene in bulbs and leaves was significantly higher than that in stem segments and roots, indicating that the most important site for amylose synthesis was the main source-sink organs. Furthermore, the LohGBSSI expression was highest at 15 d in bulblet, suggesting that rapid starch synthesis is a necessity for the early bulblet morphogenesis.  Conclusion  This study has laid a foundation for further functional analysis of GBSS in bulb development and also provided a basis for future lily starch relevant gene modification.