Details in plant breading barrier revealed
A few years ago Claudia Köhler’s lab at SLU led a study that identified a gene involved in the abortion of seeds from crosses of plants that differ in chromosome number. Now her lab presents further details explaining the molecular basis for this important obstacle to plant breeders around the world.
The article was published on-line on July 25th in Genes & Development.
The majority of modern crops are polyploid, meaning that they have more than two chromosome sets in their cells. Breeding of modern crops has not only led to an increase in ploidy, but has also caused the loss of many advantageous traits that confer resistance to pathogen attack or abiotic stress. New breeding efforts aim to introgress such "lost traits" from ancestral, non-polyploid varieties to polyploid crops, but this effort is complicated by a barrier preventing successful hybridizations of species that differ in ploidy level. This phenomenon, also called the "triploid block", has been the subject of much research, but its underlying basis has remained unknown.
A recent publication by Hua Jiang from the laboratory of Claudia Köhler revealed that interploidy hybridizations cause genome-wide chromatin changes in the endosperm, the nutritious tissue supporting embryo growth and providing the calories for human diet and animal feed. As a consequence of those chromatin changes the activity of growth-promoting genes in the endosperm is strongly enhanced, with lethal consequences for the developing seed. The authors have identified the causal genes for this phenomenon, opening new avenues to device strategies bypassing hybridization barriers.
In this study Arabidopsis thaliana was used as a model plant species. Plants with mutations at critical positions in the genome (including one that broke the "triploid block" and almost only produced viable seeds) made it possible to identify the key genes and mechanisms.
Professor Claudia Köhler
Dept. of Plant Biology
Swedish University of Agricultural Sciences, Uppsala
Hua Jiang, Jordi Moreno-Romero, Juan Santos-González, Geert De Jaeger, Kris Gevaert, Eveline Van De Slijke & Claudia Köhler. Ectopic application of the repressive histone modification H3K9me2 establishes post-zygotic reproductive isolation in Arabidopsis thaliana. Genes & Dev. 2017. 31: 1272–1287. doi: 10.1101/gad.299347.117
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Aborted triploid seeds. Photo: Hua Jiang
Triploid seeds rescued by mutations in chromatin modifying genes. Photo: Hua Jiang
Hua Jiang, first author of the article. Photo: Jun Yi