Sun Cheng, Yu Guoliang, Bao Manzhu, Zheng Bo, Ning Guogui
Key laboratory of Horticultural Plant Biology, Ministry of Education, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, P, R, China.
BMC Res Notes. 2014 Jun 27;7:402. doi: 10.1186/1756-0500-7-402.
Odd traits in few of plant species usually implicate potential biology significances in plant evolutions. The genus Helwingia Willd, a dioecious medical shrub in Aquifoliales order, has an odd floral architecture-epiphyllous inflorescence. The potential significances and possible evolutionary origin of this specie are not well understood due to poorly available data of biological and genetic studies. In addition, the advent of genomics-based technologies has widely revolutionized plant species with unknown genomic information.
Morphological and biological pattern were detailed via anatomical and pollination analyses. An RNA sequencing based transcriptomic analysis were undertaken and a high-resolution phylogenetic analysis was conducted based on single-copy genes in more than 80 species of seed plants, including H. japonica. It is verified that a potential fusion of rachis to the leaf midvein facilitates insect pollination. RNA sequencing yielded a total of 111450 unigenes; half of them had significant similarity with proteins in the public database, and 20281 unigenes were mapped to 119 pathways. Deduced from the phylogenetic analysis based on single-copy genes, the group of Helwingia is closer with Euasterids II and rather than Euasterids, congruent with previous reports using plastid sequences.
The odd flower architecture make H. Willd adapt to insect pollination by hosting those insects larger than the flower in size via leave, which has little common character that other insect pollination plants hold. Further the present transcriptome greatly riches genomics information of Helwingia species and nucleus genes based phylogenetic analysis also greatly improve the resolution and robustness of phylogenetic reconstruction in H. japonica.
少数植物物种的奇特特征通常暗示着植物进化中的潜在生物学意义。青荚叶属（Helwingia Willd）是冬青目一种雌雄异株的药用灌木，具有奇特的花结构——叶上花序。由于生物学和遗传学研究数据匮乏，该物种的潜在意义和可能的进化起源尚不清楚。此外，基于基因组学的技术的出现极大地改变了基因组信息未知的植物物种。
通过解剖学和授粉分析详细阐述了形态和生物学模式。进行了基于RNA测序的转录组分析，并基于包括青荚叶（H. japonica）在内的80多种种子植物的单拷贝基因进行了高分辨率系统发育分析。证实了叶轴与叶片中脉的潜在融合有利于昆虫授粉。RNA测序共产生了111450个单基因；其中一半与公共数据库中的蛋白质具有显著相似性，20281个单基因被映射到119条途径。从基于单拷贝基因的系统发育分析推断，青荚叶属与菊亚纲II类更接近，而不是菊亚纲，这与之前使用质体序列的报道一致。
这种奇特的花结构使青荚叶属通过叶片容纳比花大的昆虫来适应昆虫授粉，这与其他昆虫授粉植物几乎没有共同特征。此外，目前的转录组极大地丰富了青荚叶属物种的基因组信息，基于核基因的系统发育分析也大大提高了青荚叶系统发育重建的分辨率和稳健性。
