Transcriptional modules and hormonal metabolic pathways reveal the critical role of TgHB12-like in the regulation of flower opening and petal senescence in Tulipa gesneriana

Abstract Tulips (Tulipa gesneriana) are one of the most widely cultivated bulbous plants with substantial ornamental value. However, the lack of well-documented reference genomes has limited the research progress and molecular breeding of tulips. In the present study, a full-length transcriptome of a commercial tulip cultivar was obtained using single-molecule long-read sequencing (PacBio Iso-Seq). In total, 244,357 full-length transcripts were identified, which had an average length of 2,044 bp and an N50 value of 3,861; 67,350 of these were annotated to databases. An inaugural integrated analysis of the transcriptome and phytohormone profiles during flower opening and petal senescence was performed using Illumina RNA-seq, coupled with Mfuzz (an R pakage, http://mfuzz.sysbiolab.eu ) and weighted gene coexpression network analysis (WGCNA). A total of 16 gene coexpression and six transcription factor (TF) modules were constructed. Additionally, 26 hormone analogs were comprehensively profiled. Finally, a prominently novel gene, Tulipa gesneriana Homeobox12-like (TgHB12-like), which encodes an homeodomain–leucine zipper (HD-zip) TF, was identified as a pivotal regulator of petal senescence. Overall, this work facilitates the identification of hormones and TFs in plants related to flower opening and senescence in tulips. It also provides an important and valuable genetic basis for further research in them.