‘Wildly weird’ RNA bits discovered infesting the microbes in our guts Rod-shaped structures named ‘obelisks’ are even smaller than viruses but can still transmit instructions to cells

How mysterious circular DNA causes cancer in children Children are not old enough to be affected by the standard mechanism of cancer development. What, then, is the reason for childhood cancers? We were able to show that certain types of circular DNA may accelerate neuroblastoma growth,” explains Dr. Koche and adds: “Testing for their presence may therefore make it easier to predict the course of the disease.

Circular DNA is not so mysterious: it's viral plasmid routinely used in genetic manipulations as it can replicate fast in GMO plants. The fact that isn't part of main DNA gene strand is also reason, why it's mobile and highly susceptible to horizon gene transfer i.e. it can spread through viral and bacterial infections to another plants, which would then become resistant to weed killers, allergenic or even carcinogenic as well, including their pollens. See for instance:

Extrachromosomal circular DNA-based amplification and transmission of herbicide resistance in crop weed Amaranthus palmeri