Generation and classification of transcriptomes in two Croomia species and molecular evolution of CYC/TB1 genes in Stemonaceae

• Published in: Plant diversity Vol. 40; no. 6; pp. 253 - 264
• Main Authors: Lu, Ruisen, Xu, Wuqin, Lu, Qixiang, Li, Pan, Losh, Jocelyn, Hina, Faiza, Li, Enxiang, Qiu, Yingxiong
• Format: Journal Article
• Language: English
• Published: China Elsevier B.V 01.12.2018; Kunming Institute of Botany, Chinese Academy of Sciences; KeAi Communications Co., Ltd
• Subjects: Croomia; CYC/TB1; East Asia; EST-SSRs; expressed sequence tags; Flower symmetry; flowers; genomics; leaves; microsatellite repeats; monophyly; North America; SCNGs; Stemonaceae; Transcriptome; unigenes; East Asia; North America; Flower symmetry; SCNGs; Croomia; EST-SSRs; CYC/TB1; Transcriptome
• ISSN: 2468-2659; 2096-2703; 2468-2659
• DOI: 10.1016/j.pld.2018.11.006

The genus Croomia (Stemonaceae) is an excellent model for studying the evolution of the Eastern Asia (EA)–Eastern North America (ENA) floristic disjunction and the genetic mechanisms of floral zygomorphy formation. In addition to the presence of both actinomorphic and zygomorphic flowers within the genus, species are disjunctively distributed between EA and ENA. However, due to the limited availability of genomic resources, few studies of Croomia have examined these questions. In this study, we sequenced the floral and leaf transcriptomes of the zygomorphic flowered Croomiaheterosepala and the actinomorphic flowered Croomia japonica, and used comparative genomic approaches to investigate the transcriptome evolution of the two closely related species. The sequencing and de novo assembly of transcriptomes from flowers of C. heterosepala (ChFlower), flowers of C. japonica (CjFlower), and leaves of C. japonica (CjLeaf) yielded 57,193, 62,131 and 64,448 unigenes, respectively. In addition, estimation of Ka/Ks ratios for 11,566 potential orthologous groups between ChFlower and CjFlower revealed that only six pairs had Ka/Ks ratios significantly greater than 1 and are likely under positive selection. A total of 429 single copy nuclear genes (SCNGs) and 21,460 expression sequence tags-simple sequence repeats (EST-SSRs) were identified in this study. Specifically, we identified seven CYC/TB1-like genes from Stemonaceae. Phylogenetic and molecular evolution analyses indicated that these CYC/TB1-like genes formed a monophyletic clade (SteTBL1) and were subject to strong purifying selection. The shifts of floral symmetry in Stemonaceae do not appear to be correlated with TBL copy number.