Abstract
BackgroundHeterosis is biologically important but the molecular basis of the phenomenon is poorly understood. We characterized intergeneric hybrids between B. rapa cv. Chiifu and R. sativus cv. WK10039 as an extreme example of heterosis. Taking advantage of clear heterosis phenotypes and the genetic distance between parents, we performed transcriptome and metabolite analysis to decipher the molecular basis of heterosis.ResultsThe heterosis was expressed as fresh weight in the field and as inflorescence stem length in the glass house. Flowering time, distributed as a normal segregating population, ranged from the early flowering of one parent to the late flowering of the other, in contrast to the homogeneous flowering time in a typical F1 population, indicating unstable allelic interactions. The transcriptome and metabolome both indicated that sugar metabolism was altered, suggesting that the change in metabolism was linked to the heterosis. Because alleles were not shared between the hybridized genomes, classic models only partly explain this heterosis, indicating that other mechanisms are involved.ConclusionThe differential expression of genes for primary and secondary metabolism, along with the altered metabolite profiles, suggests that heterosis could involve a change in balance between primary and secondary metabolism.
Highlights
Heterosis is biologically important but the molecular basis of the phenomenon is poorly understood
F1 hybrids show hybrid vigor in shoot growth and biomass at the vegetative stage We characterized the heterosis in the phenotypes of the F1 hybrid from the cross between B. rapa cv
Because the F1 hybrid seeds were rescued from siliques that were not fully developed, it was not feasible to assess the hybrid phenotypes showing potential heterosis relative to the parents at early developmental stages, including traits such as cotyledon size, leaf size, and leaf initiating rate
Summary
Heterosis is biologically important but the molecular basis of the phenomenon is poorly understood. Taking advantage of clear heterosis phenotypes and the genetic distance between parents, we performed transcriptome and metabolite analysis to decipher the molecular basis of heterosis. The tendency of hybrids to perform better than their parents, can be observed in phenotypes such as biomass, seed number, plant height, etc. Many of these hybrid phenotypes enhance yield and other agronomically important characteristics and are exploited in a variety of breeding programs. Several classical models for heterosis were based on allelic interactions. The search remains for a possible unifying model capable of explaining the mechanism of heterosis in both plants and animals
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