块茎是油莎豆独特且极其重要的器官, 富含油脂且具有与种子类似的繁殖能力, 研究油莎豆块茎中特异性表达的基因对于解析其块茎特异性生长发育(尤其是油脂积累)的调控机理具有重要意义。通过对油莎豆主要器官(根、叶、分蘖节、匍匐茎和块茎)的转录组测序, 全面地筛选块茎中特异性表达的基因, 并分析相关基因功能。结果表明, 分别以根、叶、分蘖节、匍匐茎为参照, 经过多组比对分析之后共鉴定出155个块茎特异性表达基因; GO富集分析显示, 种子发育、种子油体合成、油脂储存、脱落酸响应、热激响应、非生物刺激响应和蛋白折叠相关的7个GO条目被显著富集, 这些GO条目涉及的基因恰好反映出油莎豆块茎独特的与种子类似的发育特性。其中, CESC_00080和CESC_16572编码油体钙蛋白, CESC_08636、CESC_12549和CESC_17828编码油体蛋白, 均参与植物油体形成, 而油体形成是植物完成油脂储存的关键步骤, 表明这些油体形成相关基因在块茎中特异性的表达可能是油莎豆在块茎中储存大量油脂的关键所在。另外, 本研究还筛选出8个块茎特异性表达转录因子编码基因, 如CESC_00448 (abscisic acid insensitive 5-like protein ABI5)和CESC_03736 (heat stress transcription factor C), 而鉴定的块茎特异性表达基因中存在一些它们潜在的靶基因, 表明这些转录因子编码基因可能调控各自靶基因的特异性表达。综上所述, 本研究结果可为油莎豆块茎发育相关的基因调控网络构建以及块茎特异性基因表达的分子机制解析提供重要的参考。

Tuber is a unique and extremely important organ of Cyperus esculentus, which is rich in oil and has the reproduction ability similar to seed. It is of great significance to study the specific expression genes in the tubers of Cyperus esculentus for analyzing the regulation mechanism of tuber-specific growth and development (especially oil accumulation). Through transcriptome sequencing of the main organs (root, leaf, tillering node, stolon and tuber) of Cyperus esculentus, the genes specifically expressed in tubers were comprehensively screened and the functions of related genes were analyzed. The results showed that a total of 155 tuber-specific expression genes were identified after multiple sets of comparative analysis by taking root, leaf, tillering node and stolon as reference, respectively. GO enrichment analysis showed that 7 GO terms including seed development, seed oilbody biogenesis, oil storage, abscisic acid response, response to heat, response to abiotic stimulus and protein folding were significantly enriched, and some of the genes involved in these GO terms just reflected the unique development characteristics similar to seed of Cyperus esculentus tubers. Among them, CESC_00080 and CESC_16572 encode caleosin, and meanwhile, CESC_08636, CESC_12549 and CESC_17828 encode oleosin, all of which are involved in the formation of plant oil bodies. Since oil body formation is a key step for plants to complete oil storage, it is indicated that the specific expression of these oil body formation-related genes in tubers may be the key to the storage of large amounts of oil in the tubers of Cyperus esculentus. In addition, this study also screened eight tuber-specific expression transcription factor genes, such as CESC_00448 (Abscisic acid insensitive 5-like protein ABI5) and CESC_03736 (Heat stress transcription factor C), some of whose potential target genes were found in identified tuber-specific expression genes, indicating that these transcription factor genes may regulate the specific expression of their respective target genes. In summary, the results of this study can provide an important reference for the construction of gene regulatory networks related to tuber development of Cyperus esculentus and the molecular mechanism analysis of tuber-specific gene expression.