pubmed.ncbi.nlm.nih.gov

Recent research on the mechanism of heterosis is important for crop and vegetable breeding systems - PubMed

Review

. 2018 Mar;68(2):145-158.

doi: 10.1270/jsbbs.17155. Epub 2018 Apr 12.

Affiliations

Review

Recent research on the mechanism of heterosis is important for crop and vegetable breeding systems

Ryo Fujimoto et al. Breed Sci. 2018 Mar.

Abstract

Heterosis or hybrid vigor is a phenomenon where hybrid progeny have superior performance compared to their parental inbred lines. This is important in the use of F1 hybrid cultivars in many crops and vegetables. However, the molecular mechanism of heterosis is not clearly understood. Gene interactions between the two genomes such as dominance, overdominance, and epistasis have been suggested to explain the increased biomass and yield. Genetic analyses of F1 hybrids in maize, rice, and canola have defined a large number of quantitative trait loci, which may contribute to heterosis. Recent molecular analyses of transcriptomes together with reference to the epigenome of the parents and hybrids have begun to uncover new facts about the generation of heterosis. These include the identification of gene expression changes in hybrids, which may be important for heterosis, the role of epigenetic processes in heterosis, and the development of stable high yielding lines.

Keywords: epigenetics; heterosis; hybrid vigor; non-additive gene expression.

PubMed Disclaimer

Figures

Fig. 1
Fig. 1

Three hypotheses to explain the genetic mechanism of heterosis. Phenotype is the sum of gene effects (A, B, A + B). (a) The dominance model; dominant alleles (A and B) suppress or complement the recessive alleles (a and b). (b) The overdominance model; heterozygosity (B1/B2) at the key locus contributes to heterosis leading to superior performance. (c) The epistasis model; non-allelic genes (A2 and B1) inherited from the parental lines interact and contribute to heterosis.

Fig. 2
Fig. 2

Classification of the mode of gene action in F1 hybrid (F1) compared with parental gene expression level (P1 or P2). LP; low parent, HP; high parent, MPV; mid-parent value.

Fig. 3
Fig. 3

Shutdown of chlorophyll biosynthesis in the cotyledon by norflurazon preventing increase of leaf area in the F1 hybrid. Left panel; plants were grown on Murashige and Skoog (MS) medium for two weeks. F1 hybrids show heterosis in the first and second leaves. Middle panel; seeds were sown on MS medium and grown for one week. The seedlings were transferred to MS medium with 1 μM norflurazon and grown for another two weeks. F1 hybrids show heterosis in the first and second leaves. Right panel; seeds were sown on MS medium with 1 μM norflurazon and grown for one week, then transferred to MS medium for three weeks. Plants did recover chlorophyll biosynthesis after removal of norflurazon. However, F1 hybrids do not show heterosis in the third and fourth leaves.

Fig. 4
Fig. 4

Schematic diagram illustrating the maintenance and de novo DNA methylation via RNA-dependent DNA methylation (RdDM) pathway. AGO4, ARGONAUTE 4; CMT2, CHROMOMETHYLASE 2; CMT3, CHROMOMETHYLASE 3; DCL3, DICER-LIKE 3; DDM1, DECREASE IN DNA METHYLATION 1; DRM2, DOMAINS REARRANGED METHYLTRANSFERASE 2; KYP, KRYPTONITE; MET1, METHYLTRANSFERASE 1; Pol IV, RNA Polymerase IV; Pol V, RNA Polymerase V RDR2, RNA-DEPENDENT RNA POLYMERASE 2; 24-nt siRNA, 24 nucleotide small interfering RNA. mCG, mCHG, and mCHH represent DNA methylation at CG, CHG, and CHH sites (H is A, T, or C), respectively.

Fig. 5
Fig. 5

Change of DNA methylation state in the F1 hybrid. Trans-chromosomal methylation (TCM); gaining DNA methylation of an allele with low methylation. siRNA derived from parent with high methylation level can cause TCM. Trans-chromosomal demethylation (TCdM); loss of DNA methylation by loss of siRNA at a genomic segment.

Fig. 6
Fig. 6

A trade-off between expression of defense response genes and growth heterosis. Repressors affect defense response genes (R1 or R2), and repression of these genes result in enhanced growth (G1 or G2). Parents (P1 or P2) have a balance between expression of defense response genes and growth, while F1 emphasizes growth at the expense of the expression of defense response genes.

Fig. 7
Fig. 7

Possible pathway of heterosis in A. thaliana. Heterosis is dependent on the increased photosynthesis by increased leaf area, and DECREASE IN DNA METHYLATION 1 (DDM1) plays a role in increasing leaf area of F1 hybrids. Left bottom picture represents seedlings at 28 days after sowing, and the F1 having homozygous ddm1 mutations reduces vegetative heterosis.

Similar articles

Cited by

References

    1. Abdelnoor, R.V., Yule, R., Elo, A., Christensen, A.C., Meyer-Gauen, G. and Mackenzie, S.A. (2003) Substoichiometric shifting in the plant mitochondrial genome is influenced by a gene homologous to MutS. Proc. Natl. Acad. Sci. USA 100: 5968–5973. - PMC - PubMed
    1. Alonso-Peral, M.M., Trigueros, M., Sherman, B., Ying, H., Taylor, J.M., Peacock, W.J. and Dennis, E.S. (2017) Patterns of gene expression in developing embryos of Arabidopsis hybrids. Plant J. 89: 927–939. - PubMed
    1. Barber, W.T., Zhang, W., Win, H., Varala, K.K., Dorweiler, J.E., Hudson, M.E. and Moose, S.P. (2012) Repeat associated small RNAs vary among parents and following hybridization in maize. Proc. Natl. Acad. Sci. USA 109: 10444–10449. - PMC - PubMed
    1. Barth, S., Busimi, A.K., Friedrich Utz, H. and Melchinger, A.E. (2003) Heterosis for biomass yield and related traits in five hybrids of Arabidopsis thaliana L. Heynh. Heredity (Edinb) 91: 36–42. - PubMed
    1. Becker, C., Hagmann, J., Müller, J., Koenig, D., Stegle, O., Borgwardt, K. and Weigel, D. (2011) Spontaneous epigenetic variation in the Arabidopsis thaliana methylome. Nature 480: 245–249. - PubMed

Publication types

LinkOut - more resources