… for the notion that there is no such thing as Junk DNA.
https://www.science.org/content/article/moss-project-takes-step-toward-first-artificial-plant-genome
Some money quotes:
Researchers have crafted synthetic genomes for several types of bacteria, and an 18-year-long project to do the same for brewer’s yeast is close to completion. Now, a group in China has tackled a multicellular organism, synthesizing part of the genome of a type of moss. The achievement, reported last week in Nature Plants, could smooth the way for creating artificial genomes for other multicellular organisms—and for turning the moss into a factory for medicines and other products.
The Chinese team only reworked part of one chromosome in its chosen species, the spreading earthmoss (Physcomitrium patens). But the work is “a necessary step” toward a fully artificial plant genome, says Ian Ehrenreich, a synthetic genomicist at the University of Southern California. It is also “a wake-up call to people who think that synthetic genomes are only for microbes,” adds synthetic biologist Tom Ellis of Imperial College London.
For simplicity’s sake, the Chinese project, dubbed SynMoss, started with part of the short arm of chromosome 18, the smallest such limb in the plant’s 26-chromosome genome. The researchers then set about trimming and tidying the DNA. They eliminated transposons, mobile DNA elements found in eukaryotes; added short labels to mark the altered arm; standardized the three-letter genetic codes that halt protein synthesis; and made other tweaks. In total, they shrank that section of the chromosome by 56%. Then, the scientists introduced the now partly synthetic structure into individual moss cells and nurtured their growth.
The resulting plants appeared normal. They were the same size and shape as unaltered moss, grew reproductive structures, and produced spores. The modified plants were just as resistant to high salt levels and other stresses as their natural counterparts. However, the team found that some genes in the synthetic region were more active than normal, a change that could be damaging.
The results support the contentious view that transposons aren’t essential for multicellular eukaryotes. The finding won’t end the controversy over whether these sequences are beneficial or harmful, says plant synthetic biologist Jennifer Nemhauser of the University of Washington. But for scientists who argue they are advantageous, “the challenge has been set,” she says.
Lest the deniers get all excited about “However, the team found that some genes in the synthetic region were more active than normal, a change that could be damaging”, this result probably bolsters the case for junk DNA. This is because large swaths of repetitive DNA establish zones where transcription doesn’t happen (in other words, where there is no function, in other words, where there is junk), and removing the constraints is what likely leads to higher expression.
Looking forward to the day I can order a plant chromosome from Addgene.