Reconstruction of the full-length transcriptome of cigar tobacco without a reference genome and characterization of anion channel/transporter transcripts.

Background: Cigar wrapper leaves are the most important raw material of cigars. Studying the genomic information of cigar tobacco is conducive to improving cigar quality from the perspective of genetic breeding. However, no reference genome or full-length transcripts at the genome-wide scale have been reported for cigar tobacco. In particular, anion channels/transporters are of high interest for their potential application in regulating the chloride content of cigar tobacco growing on coastal lands, which usually results in relatively high Cl accumulation, which is unfavorable. Here, the PacBio platform and NGS technology were combined to generate a full-length transcriptome of cigar tobacco used for cigar wrappers.

Results: High-quality RNA isolated from the roots, leaves and stems of cigar tobacco were subjected to both the PacBio platform and NGS. From PacBio, a total of 11,652,432 subreads (19-Gb) were generated, with an average read length of 1,608 bp. After corrections were performed in conjunction with the NGS reads, we ultimately identified 1,695,064 open reading frames including 21,486 full-length ORFs and 7,342 genes encoding transcription factors from 55 TF families, together with 2,230 genes encoding long non-coding RNAs. Members of gene families related to anion channels/transporters, including members of the SLAC and CLC families, were identified and characterized.

Conclusions: The full-length transcriptome of cigar tobacco was obtained, annotated, and analyzed, providing a valuable genetic resource for future studies in cigar tobacco.