Changes in DNA-methylation during zygotic embryogenesis in interspecific hybrids of beans (Phaseolus ssp.)

Hybrid embryos resulting from crosses between Phaseolus species often fail to reach maturity and some combinations frequently abort at early developmental stages. The genetic or molecular basis for these consistent developmental defects is at present not clear. However, an extremely complex genetic system, thought to be caused by major epigenetic changes associated with gene expression changes, has been shown to be active in plant species. We have investigated DNA methylation in two interspecific hybrids, Phaseolus vulgaris x Phaseolus coccineus and its reciprocal crosses, using methylation sensitive amplification polymorphism (MSAP). The potential use of MSAP for detecting methylation variation during embryogenesis in interspecific hybrids is discussed. Significant differences in the DNA methylation patterns were observed in abortive (interspecific hybrids) and non abortive (parental) genotypes. Taken together, our results strongly suggest that generalized alterations in DNA methylation profiles could play a causative role in early interspecific embryo abortion in vivo. A considerable change in the methylation pattern during embryogenesis could be involved in the disruption of the regulation or maintenance of the embryogenesis process of Phaseolus interspecific hybrids. The results also support the earlier hypothesis that DNA methylation is critical for the regulation of plant embryogenesis and gene expression.