Heritability and Reversibility of DNA Methylation Induced by in vitro Grafting between Brassica juncea and B. oleracea

Abstract

Grafting between tuber mustard and red cabbage produced a chimeric shoot apical meristem (SAM) of TTC, consisting of Layers I and II from Tuber mustard and Layer III from red Cabbage. Phenotypic variations, which mainly showed in leaf shape and SAM, were observed in selfed progenies GSn (GS = grafting-selfing, n = generations) of TTC. Here the heritability of phenotypic variation and its association with DNA methylation changes in GSn were investigated. Variation in leaf shape was found to be stably inherited to GS5, but SAM variation reverted over generations. Subsequent measurement of DNA methylation in GS1 revealed 5.29–6.59% methylation changes compared with tuber mustard (TTT), and 31.58% of these changes were stably transmitted to GS5, but the remainder reverted to the original status over generations, suggesting grafting-induced DNA methylation changes could be both heritable and reversible. Sequence analysis of differentially methylated fragments (DMFs) revealed methylation mainly changed within transposons and exon regions, which further affected the expression of genes, including flowering time- and gibberellin response-related genes. Interestingly, DMFs could match differentially expressed siRNA of GS1, GS3 and GS5, indicating that grafting-induced DNA methylation could be directed by siRNA changes. These results suggest grafting-induced DNA methylation may contribute to phenotypic variations induced by grafting.

Maintenance of grafting‐induced epigenetic variations in the asexual progeny of Brassica oleracea and B. juncea chimera

“…Despite its long history and use in production and research, grafting‐induced variation, particularly in distant‐grafting systems, and its inheritance in progeny are not well understood. We previously investigated the exchange of heterologous sRNAs in grafting chimera (Li et al ., ), and the heritability and reversibility of grafting‐induced DNA methylation changes in sexual progeny has also been reported (Cao et al ., ). The primary aims of this current study were to determine whether grafting‐acquired changes in methylation are induced by changes in sRNAs profiles, and to establish how the epigenetic variations are maintained during cell propagation and regeneration.…”

“…Total sRNA tags were identified by BLAST analysis of the miRBase, GenBank, Rfam and Exon/Intron databases (Saxonov et al ., ; Meyers et al ., ; Benson et al ., ; Nawrocki et al ., ). The siRNAs were predicted using the tag2siRNA software (Cao et al ., ) and mapped to the DMGs via BLAST analysis of the NCBI database (http://blast.ncbi.nlm.nih.gov/Blast.cgi). The siRNA expression levels were normalized by the TPM value using the following formula: TPM = R1*1e6/total mapped reads (R1 represents the counts of a siRNA).…”

“…Recently, Cao et al . () reported that some epigenetic alterations in the sexual progeny of grafting chimera between Brassica juncea and B. oleracea could be stably transmitted to the fifth generation. Although many researchers have investigated the basis of grafting variation and inheritance (Pandey, ; Molnar et al ., ; Tsaballa et al ., ; Fuentes et al ., ), the intrinsic mechanisms are largely unknown, and so elucidating how alterations are maintained during cell propagation and regeneration is an important goal.…”

Transcriptomic Analysis of Dark-Induced Senescence in Bermudagrass (Cynodon dactylon)

“…The expression levels of DEGs were performed by qRT-PCR following the previously described method [52]. In brief, cDNA synthesis was performed using a PrimeScript RT reagent kit (Takara, Dalian, China).…”

Comparison of the Metabolites and Carotenoids between a Graft Chimera ‘Hongrou Huyou’ (Citrus unshiu + C. changshan-huyou) and Two Donors

“…Then, we are wondering whether the genes from O and C are co-expressed in OCC, or only expressed one gene from one donor. Furthermore, in the graft chimeras Brassica juncea and B.oleracea, sequence analysis revealed that DNA methylation will affect the flowering time-and gibberellin response-related genes expressions, and may lead to the phenotypic variations in progenies [39]. According to the studies discussed above, chemical substances variations herein observed in OCC also suggested that whether the gene sequences of same gene in two donors were consistent, if not, will DNA methylation exist to influence chemical-related gene expression in OCC, and how these genes coordinate to regulate substances quantities are valuable to study more.…”