Abstract
Chimeras have been used to study the transmission of genetic material and the resulting genetic variation. In this study, two chimeras, TCC and TTC (where the origin of the outer, middle, and inner cell layers, respectively, of the shoot apical meristem is designated by a ‘T’ for tuber mustard and ‘C’ for red cabbage), as well as their asexual and sexual progeny, were used to analyse the mechanism and the inheritance of the variation induced by grafting. Asexual TCC progeny were obtained by adventitious shoot regeneration, while TTC sexual progeny were produced by self-crossing. This study observed similar morphological variations in both the asexual and sexual progeny, including changes in leaf shape and the pattern of shoot apical meristem termination. The leaf shape variation was stable, while the rate of shoot apical meristem termination in the TTC progenies decreased from 74.52% to 3.01% after three successive rounds of self-crossing. Specific red cabbage small RNAs were found in the asexually regenerated plants (rTTT) that were not present in TTT, indicating that small RNAs might be transmitted from red cabbage to tuber mustard during grafting. Moreover, in parallel with the variations in phenotype observed in the progeny, some conserved miRNAs were differentially expressed in rTTT and TTT, which correlated with changes in expression of their target genes. These results suggest that the change in small RNA expression induced by grafting may be an important factor for introducing graft-induced genetic variations, providing a basis for further investigating the mechanism of graft-induced genetic variation through epigenetics.
Highlights
Plant grafting is a well-recognized means of vegetative propagation
In parallel with the variations in phenotype observed in the progeny, some conserved miRNAs were differentially expressed in reverted TTT (rTTT) and TTT, which correlated with changes in expression of their target genes
The present study further investigates two of these periclinal chimeras, TCC and TTC
Summary
Plant grafting is a well-recognized means of vegetative propagation. It differs from sexual breeding in that it involves germ cells that have undergone meiotic recombination. Graft-induced genetic variations (GIGVs) in graft offspring have been well documented in several different experimental systems and plant species (Frankel, 1954; Yagishita, 1961; Ohta and Choung, 1975; Hirata, 1979, 1980a, 1980b; Hirata et al, 1986, 1989; Hirata and Yagishita, 1986; Taller et al, 1998). An earlier study using male sterile petunia for the stock and normal fertile petunia as the scion showed that the male sterility of the stock was transferred to the scion progeny (Frankel, 1954). A later study reported the appearance of genetic variations in mung bean progeny following grafting of the mung bean seedling
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