Yang Lei, Cheng Tian-Yin, Zhao Fei-Yan
Laboratory of Molecular Physiology, College of Veterinary Medicine, Hunan Agricultural University, Changsha, Hunan Province, 410128, People's Republic of China.
Laboratory of Molecular Pathology, College of Veterinary Medicine, Hunan Agricultural University, Changsha, 410128, People's Republic of China.
BMC Genet. 2017 Feb 22;18(1):18. doi: 10.1186/s12863-017-0485-7.
Although Pomacea canaliculata is native to South and Central America, it has become one of the most abundant invasive species worldwide and causes extensive damage to agriculture and horticulture. Conventional physical and chemical techniques have been used to eliminate P. canaliculata, but the effects are not ideal. Therefore, it is important to devise a new method based on a greater understanding of the biology of P. canaliculata. However, the molecular mechanisms underlying digestion and absorption in P. canaliculata are not well understood due to the lack of available genomic information for this species, particularly for digestive enzyme genes.
In the present study, hepatopancreas transcriptome sequencing produced over 223 million high-quality reads, and a global de novo assembly generated a total of 87,766 unique transcripts (unigenes), of which 19,942 (22.7%) had significant similarities to proteins in the UniProt database. In addition, 296,675 annotated sequences were associated with Gene Ontology (GO) terms. A Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment was performed for the unique unigenes, and 262 pathways (p-value < 10) in P. canaliculata were found to be predominantly related to plant consumption and coarse fiber digestion and absorption. These transcripts were classified into four large categories: hydrolase, transferase, isomerase and cytochrome P450. The Reads Per Kilobase of transcript per Million mapped reads (RPKM) analysis showed that there were 523 down-regulated unigenes and 406 up-regulated unigenes in the starving apple snails compared with the satiated apple snails. Several important genes are associated with digestion and absorption in plants: endo-beta-1, 4-glucanase, xylanase, cellulase, cellulase EGX1, cellulase EGX3 and G-type lysozyme genes were identified. The qRT-PCR results confirmed that the expression patterns of these genes (except for the longipain gene) were consistent with the RNA-Seq results.
Our results provide a more comprehensive understanding of the molecular genes associated with hepatopancreas functioning. Differentially expressed genes corresponding to critical metabolic pathways were detected in the transcriptome of starving apple snails compared with satiated apple snails. In addition to the cellulase gene, other genes were identified that may be important factors in plant matter metabolism in P. canaliculata, and this information has the potential to expedite the study of digestive physiology in apple snails.
尽管福寿螺原产于南美洲和中美洲，但它已成为全球分布最广泛的入侵物种之一，对农业和园艺造成了广泛破坏。传统的物理和化学技术已被用于消灭福寿螺，但效果并不理想。因此，在更深入了解福寿螺生物学特性的基础上设计一种新方法很重要。然而，由于缺乏该物种的可用基因组信息，特别是消化酶基因的信息，福寿螺消化和吸收的分子机制尚未得到充分了解。
在本研究中，肝胰腺转录组测序产生了超过2.23亿条高质量 reads，通过从头组装共生成了87,766个独特转录本（单基因），其中19,942个（22.7%）与UniProt数据库中的蛋白质具有显著相似性。此外，296,675个注释序列与基因本体论（GO）术语相关联。对独特单基因进行了京都基因与基因组百科全书（KEGG）通路富集分析，发现福寿螺中有262条通路（p值<10）主要与植物消耗以及粗纤维消化和吸收有关。这些转录本分为四大类：水解酶、转移酶、异构酶和细胞色素P450。每百万映射reads中每千碱基转录本的reads（RPKM）分析表明，与饱食福寿螺相比，饥饿福寿螺中有523个下调单基因和406个上调单基因。鉴定出了几个与植物消化和吸收相关的重要基因：内切-β-1,4-葡聚糖酶、木聚糖酶、纤维素酶、纤维素酶EGX1、纤维素酶EGX3和G型溶菌酶基因。qRT-PCR结果证实这些基因（除长肽酶基因外）的表达模式与RNA-Seq结果一致。
我们的结果为与肝胰腺功能相关的分子基因提供了更全面的理解。与饱食福寿螺相比，在饥饿福寿螺的转录组中检测到了与关键代谢途径相对应的差异表达基因。除纤维素酶基因外，还鉴定出了其他可能是福寿螺植物物质代谢重要因素的基因，这些信息有可能加快福寿螺消化生理学的研究。
