Fig. 8

LTR retrotransposons regulate heat stress tolerance in moso bamboo. When transgenic moso bamboo seedling treated with heat stress, heat-dependent transcription factors, such as TCP20, DOF2, and GATA, bind to the LTR promoter of PHRE1/PHRE2 to initiate transcription of mRNA from the PHRE1/PHRE2. In the cytoplasm, the mRNA encodes GAG and POL proteins which make virus-like particles (VLP) with reverse transcriptase to produce cDNA of PHRE1/PHRE2. Then, this cDNA is imported into the nucleus and integrated into the genome. LTR retrotransposons are also involved in epigenetic TE repression. The hairpin structure double-stranded RNA is produced from the mRNA of PHRE1/PHRE2. The dicer enzyme cleaves the double-stranded RNA into 21–25 nucleotide long siRNAs. Then, the siRNA was loaded onto the RISC complex where one strand is degraded and the other strand works as a template (antisense to the TE mRNA or gene mRNA) to post-transcriptionally silence the mRNA expression or this complex is transported to the nucleus, to initiate the RNA-directed DNA methylation (RdDM), to epigenetically induce transcriptional gene silencing or transposable elements