LncRNAs in polyploid cotton interspecific hybrids are derived from transposon neofunctionalization

Interspecific hybridization and whole genome duplication are driving forces of genomic and organism diversification. But the effect of interspecific hybridization and whole genome duplication on the non-coding portion of the genome in particular remains largely unknown. In this study, we examine the profile of long non-coding RNAs (lncRNAs), comparing them with that of coding genes in allotetraploid cotton (Gossypium hirsutum), its putative diploid ancestors (G. arboreum; G. raimondii), and an F₁ hybrid (G. arboreum × G. raimondii, AD).

We find that most lncRNAs (80%) that were allelic expressed in the allotetraploid genome. Moreover, the genome shock of hybridization reprograms the non-coding transcriptome in the F₁ hybrid. Interestingly, the activated lncRNAs are predominantly transcribed from demethylated TE regions, especially from long interspersed nuclear elements (LINEs). The DNA methylation dynamics in the interspecies hybridization are predominantly associated with the drastic expression variation of lncRNAs. Similar trends of lncRNA bursting are also observed in the progress of polyploidization. Additionally, we find that a representative novel lncRNA XLOC_409583 activated after polyploidization from a LINE in the A subgenome of allotetraploid cotton was involved in control of cotton seedling height.

Our results reveal that the processes of hybridization and polyploidization enable the neofunctionalization of lncRNA transcripts, acting as important sources of increased plasticity for plants.