Genes, seed development | Findings have significant implications for global agriculture and food security
LINDELL BEACH, B.C. — A gene has been identified for the first time that regulates the optimum amount of nutrients that flow from “mother” to “offspring” in corn plants.
The research was led by scientists at the University of Warwick in collaboration with the University of Oxford and the agricultural biotech research company Biogemma, all located in the United Kingdom.
The gene is Meg1, which, unlike most genes that are expressed from both maternal and paternal chromosomes, is expressed only from the maternal chromosomes.
“It is well known that in humans, placental growth is controlled by the action of uniparentally expressed or ‘imprinted’ genes,” said Jose Gutierrez-Marcos, associate professor with the University of Warwick’s School of Life Sciences.
Read Also
British Columbia farmers to receive increased AgriStability supports
B.C. farmers to receive bump in AgriStability compensations due to weather concerns, international trade instability
“We decided a decade ago to initiate a molecular screen to identify plant-imprinted genes and test if this phenomenon also occurred in the placental-like seed endosperm of flowering plants. From this initial study, we identified Meg1 amongst numerous other genes, which exhibited maternal-only expression in early developing endosperms.”
This unusual form of uniparental expression, also called imprinting, isn’t restricted to plants. It is also found in some human genes that are known to regulate the development of the placenta to control the supply of maternal nutrients during fetal growth.
While scientists have known for some time of the existence of such imprinted genes in humans and other mammals, this is the first time a parallel gene to regulate nutrient flow during seed development has been identified in the plant world.
It means scientists can now focus on using the gene and further the understanding of the mechanism by which it is expressed to increase seed size and productivity in major crop plants.
“Uniparental expression in plants is highly significant as it doesn’t fit with the classic view of genetics and also shows that flowering plants and mammals have co-opted similar epigenetic mechanisms to regulate the growth and development of their placental-like organs, and ultimately the offspring,” said Gutierrez-Marcos.
“These findings have significant implications for global agriculture and food security, as scientists now have the molecular know-how to manipulate this gene by traditional plant breeding or through other methods to improve seed traits such as increased seed biomass yield.”
He said researchers have evidence for only a small fraction of genes — less than 200 out of the 40,000 corn genes — that show expression only from one of the inherited parental genomes, mostly those being maternal.
“It has been hypothesized that imprinted gene expression allows parents to uniquely contribute gene products (proteins) important for the development of their offspring, thereby promoting sexual reproduction,” he said.
“It is unclear why the majority of imprinted genes in plants are maternally expressed, though it may be likely linked to increased fitness of the mother. Intriguingly, imprinted expression occurs mostly in the endosperm tissue within the seed.”
The placenta and endosperm are embryo-nourishing organs, both of which result from fertilization of male and female gametes. He said it was surprising that flowering plants and mammals have evolved similar mechanisms to support the growth of these organs and the offspring with little impact on the embryo-bearing mother.
“A few imprinted genes have now been identified in mice, which analogous to Meg1, appear to regulate the differentiation and function of specialized nutrient transfer cell-like structures within the placenta,” he said.
“Also, a few genes, though mostly with paternal monoallelic expression, have been identified in the placenta, which act to regulate the supply and demand of nutrients to the embryo.”
The application of this research could be enormous.
“The most immediate application could be the redesign of breeding programs in crops to take into consideration imprinted gene expression,” he said.
“The main strategy would be to exploit the naturally occurring genetic diversity at the Meg1 locus in maize for changes in imprinted gene regulation and relative expression levels.”
He said this understanding of how corn seeds and other cereal grains develop will be vital because the global population relies on these stable products for sustenance.
“While the identification of Meg1 is an important discovery in its own right, it also represents a real breakthrough in unravelling the complex gene pathways that regulate the provisioning and nutritional content of seeds,” said professor Hugh Dickinson of Oxford University’s plant sciences department.
