How information beyond the genetic sequence is encoded in plant sperm – sciencedaily


Hereditary information is passed from parents to offspring in genetic code, DNA and epigenetically through chemically induced changes around DNA.

New research from the John Innes Center has discovered a mechanism that adjusts these changes, altering the way information beyond the genetic code is passed from generation to generation.

DNA methylation, an example of such epigenetic changes, occurs when a methyl group or chemical cap is added to DNA, turning one or more genes on or off.

As the germ cells (eggs and sperm) develop, some of the methyl markers are reset, affecting the information passed on to the next generation.

How this process works during plant reproduction is unclear.

The exciting research, published in Science, reveals the molecular mechanism of the reprogramming of DNA methylation in the male germ line of plants.

Inside the plant’s male reproductive organs (the anthers), cells that will divide to produce sperm (meiocytes) are surrounded by cells that nourish them. These feeder cells are called tapetal cells.

The John Innes Center team discovered that carpet cells produce an abundance of small RNA molecules and observed that this is caused by a protein called CLSY3, found specifically in anther carpet cells. These small RNAs have been shown to move from tapetal cells to meiocytes. Here they add new methyl marks to transposons (unstable genetic elements) with the same DNA code.

“This discovery changes the way we think about epigenetic inheritance across generations in plants. Small RNAs produced by germline feeder cells can determine the DNA methyloma in sperm. The key role played by these small RNAs in the determination of the methylome of inherited DNA indicates a convergent functional evolution between plant and animal reproduction, ”explains the corresponding author, Dr. Xiaoqi Feng, group leader at the John Innes Center.

This reprogramming prevents transposons from jumping into germ cells, which protects the integrity of the genome between generations.

In meiocytes, these small RNAs also target genes with DNA sequences similar to those of source transposons, helping to control gene expression and facilitate meiosis, a type of cell division that leads to the production of sperm. .

The results have wide application in the plant and animal kingdoms and provide a vital new clue for the global community of researchers studying epigenetics. Previous work has shown that cereal crops, like corn and rice, have similar small tapetal RNAs, however, it was not clear why these small RNAs are important for fertility and yield. The mechanistic information generated by this study points to new directions of investigation and may help develop biotechnology to target DNA methylation in cash crops.

Joint first author Dr Jincheng Long said, “Our study could pave the way for crop biotechnology. For example, through the manipulation of DNA methylation directed by small RNAs in contributing cells. directly to seed formation and the breeding process. ”

The study is also important in fundamental biological terms, explains first joint author Dr. James Walker, “Our work demonstrates that paternal epigenetic inheritance is determined by tapetal cells, which cause reprogramming on an unprecedented scale in plants.

“The molecular mechanism revealed by our work takes our understanding of de novo DNA methylation to the next level, showing how new methyl marks are established at specific sites in specific cells.”


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