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[摘要]
目的 分析遮阴对地黄块根性状和叶片光合特性的影响,并通过转录组测序阐明遮阴抑制地黄块根膨大的分子机制。方法 对地黄进行全光照、60%遮阴、90%遮阴处理,测块根性状及光合特性。利用高通量测序技术对90%遮阴处理和自然光照的地黄块根进行转录组测序,筛选差异表达的基因,同时,利用实时荧光定量PCR对部分基因在根和叶中的表达特性进行分析。结果 遮阴后块根长度、直径和单株块根产量均显著降低,90%遮阴处理块根几乎不膨大。地黄块根中薄壁细胞层数减少,导管比例升高。随遮阴程度增加叶绿素a、b及总叶绿素含量逐渐降低,光合能力下降。转录组分析共获得3 348个差异表达的基因,其中1 396个下调,1 952个上调;通过KEGG代谢通路富集分析,将遮阴后差异表达的1 668个基因(53.4%)富集到117个代谢通路中,其中17个代谢通路富集达到显著水平。植物激素信号传导通路最先得到富集,其次是植物病原菌互作通路,苯乙醇苷生物合成通路、淀粉和蔗糖代谢通路也得到了显著富集。在激素信号通路中,多数基因上调表达。遮阴后差异表达的16个扩展蛋白基因中11个下调表达,仅有5个上调表达,与淀粉降解有关的2个β-淀粉酶基因(Bmy)基因均上调表达,而蔗糖磷酸合成酶基因(SPS)下调表达,参与木质素合成的多数基因下调表达,纤维素合成基因多数上调表达。结论 遮阴后地黄光合能力下降,光合产物减少,地黄通过一系列激素通路基因的差异表达对遮阴作出响应调控,使块根膨大受阻。
[Key word]
[Abstract]
Objective To reveal the effects of shading on tuberous root and photosynthetic characteristics of Rehmannia glutinosa, and analyze the molecular mechanism of shading affecting the expansion of R. glutinosa tuberous root by transcriptome sequencing. Methods R. glutinosa plants were treated with full light, 60% shading and 90% shading. High-throughput sequencing was used to sequence the transcriptome of the R. glutinosa tuberous roots treated with full-light and 90% shading, and the differentially expressed genes were screened out. The expression characteristics of some genes in tuberous roots and leaves were analyzed by real-time fluorescence quantitative PCR. Results After shading, the number of parenchyma cell layers in the tuberous roots was decreased, but the proportion of ducts was increased, the length, diameter and fresh weight of tuberous roots were decreased significantly, and the tuberous roots barely expanded under 90% shading treatment. The number of parenchyma cell was decreased and the proportion of duct was increased in root tubers of R. glutinosa. With the increase of shading degree, the content of chlorophyll a and b and total chlorophyll content were gradually decreased, and photosynthetic capacity was decreased. A total of 3 348 differentially expressed genes were obtained by transcriptome analysis, of which 1 396 were down-regulated and 1 952 were up-regulated. Through enrichment analysis of KEGG metabolic pathway, 1 668 differentially expressed genes (53.4%) were enriched into 117 metabolic pathways, and 17 of them were significantly enriched pathways. The plant hormone signaling pathway was enriched firstly, followed by the plant pathogen interaction pathway, the phenylethanoid glycoside biosynthesis pathway, starch and sucrose metabolic pathways were also enriched significantly. In the hormone signaling pathway, most of different expressed genes were up-regulated. Eleven expansin genes were down-regulated under 90% shading, only five expansin genes were up-regulated. Two of beta-amylase genes (Bmy) related to starch degradation were up-regulated when shading treated, while the sucrose phosphate synthase genes (SPS) were down-regulated. Most of the genes involved in lignin synthesis were down-regulated and most of the genes involved in cellulose synthesis were up-regulated. Conclusion The photosynthetic capacity of R. glutinosa was decreased under shading conditions, and led to the accumulation of photosynthate decreased in its leaf and tuberous root. R. glutinosa plant responded to shading by regulating the differential expression of a series of hormone pathway genes, which prevent the expansion of tuberous roots.
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[基金项目]
国家重点研发计划项目(2017YFC1700705);国家自然科学基金资助项目(81872950);国家自然科学基金资助项目(81473299)