旱垂柳转录组测序及赤霉素在垂枝形成中的作用

Transcriptome Sequencing and the Function of Gibberellin in Weeping Branches of Salix matsudana var. pseudo-matsudana

垂枝作为特殊的林木形态结构,因形态优美在全世界被广泛用于绿化和园林景观而成为研究热点。国内外对垂枝植物的研究表明赤霉素在垂枝形成中起作用,但是垂枝形成的分子背景研究仍比较缺乏。本研究以旱垂柳(Salix matsudana var. pseudo-matsudana)的垂枝为研究对象,通过对旱垂柳在不同生长发育时期的叶片、茎尖和茎基部进行了转录组和数字表达谱测序研究,共获得71 474个Unigenes序列。将Unigenes与COG和KEEG数据库比对,与转录和信号转导机制相关的基因在旱垂柳中高度富集,最终确定8 359个差异表达的基因,其中427个基因与激素相关。进一步分析赤霉素相关基因得出,主要参与2条赤霉素合成途径,具有生物活性的GA4是合成途径中的主要产物,而且GA4在枝条中的含量显著高于GA1和GA3。参与赤霉素信号转导途径中的GID1B在旱垂柳中上调表达,以及在G1和G4生长期的表达量高于其他时期,而DELLA蛋白GAI在G2生长期以后下调表达,GID1B和GAI在旱垂柳的垂枝生长过程中可能起非常重要的作用。这些研究结果将有助于探索赤霉素在旱垂柳垂枝形成中的分子作用,可为林木形态的遗传改良提供基础理论依据。

Being a specific tree archi tecture, weeping species are used worldwide as landscape plant. Weeping trait(pendulous-branched) has received increasing attention during the past years. Based on current analysis of various weeping species, plant hormone of gibberellin was may be r esponsible for weeping trait. However, the molecular mechanism of weeping trait remains poorly defined. In order to study the molecular basis for weeping trait of Salix matsudana var. pseudo-matsudana, leaves and stems collected at different developmental stages were analyzed using RNA-seq coupled with digital gene expression. In total 71 474 unigenes were obtained. Based on BLAST search against COG and KEEG databases, most of unigenes were annotated with transcription and signal transduction. A total of 8 359 genes were differentially expressed in willow development. Among these, 427 genes were related to hormones. Genes related to gibberellin were screened for further comparative analysis. We found that these genes were involved in two main gibberellin biosynthesis pathways and GA4 was the dominant bioactive gibberellin. Meanwhile, the GA4 concentrations in the stems were higher than GA1 and GA3. Differentially expressed genes associated with gibberellin signal transduction pathways were identified. The high expression of GIDB occurred at G1 and G4. GIDB were up-regulated while DELLA protein GAI were down-regulated after G2.The interaction of GID1 B and GAI were highly likely to be responsible for the weeping trait. These results will be helpful to discuss the function of gibberellin in development of weeping trait in willow at the molecular level.Thus, our data provide valuable information for genetic improvement in morphological structure.