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frojack writes:

In an interesting feedback loop, some parts of plants are able to modify the genetic expression of their own nucleus in real time in a way not yet fully understood.

An interesting article in ArsTechnica summarizes a paywalled article in Science describing how Chloroplasts (in the leaves of plants) control the RNA transcription process in the roots of plants by a mechanism not yet determined.

Chloroplasts, billions of years ago were free-living individual cells. However, by a mechanism still only guessed at, they became entrapped in plant cells, and persist today in the leaves of every green plant.

The Chloroplasts appear to control, in real time, the RNA transcription process in remote parts of the plant (roots), turning on and off the expression of certain parts of the plant's own DNA.

Some of the genes in the nucleus are recipes for cellular machinery needed for the chloroplast to do its job:to undertake photosynthesis. It is important that the nucleus transcribes these genes in response to appropriate cues, especially daylight.

Intriguingly, some genes are transcribed based on a signal that comes from the chloroplast itself. Signaling from the chloroplast to the nucleus is called retrograde signalling. It has fascinated scientists for decades because the nature of the signal from the chloroplast is unknown.

Now this story has become even more intriguing. According to the Science paper, it seems that this form of signalling from chloroplasts can do more than direct the transcription of genes. It can also direct modifications of the RNA transcribed from the genes. These transcripts are modified by splicing the RNA, which removes bits of superfluous information from them. Without splicing, most RNAs wouldn't be able to encode proteins.

The Chloroplasts, (long thought to be a captive within plant cells) effectively wrests control of the cell's chemical machinery from the nucleus by signaling (by means unknown) a change in the RNA transcription and splicing process, so as to assure themselves of the raw materials needed to carry out photosynthesis. (Of course this helps both sides of this quasi-symbiotic existence.) This "Post Processing" of the transcription process (directly modifying the transcribed RNA) is quite unique.

The signaling to do this is able to reach distant portions of the plant, usually root cells, from the leaves, in relatively short time periods.

If the Chloroplasts are able to control cellular machinery, from outside the nucleus, it calls into question which cellular life form incorporated the other. Perhaps all green plants are merely zombies controlled for eons by structures they found tasty a billion years ago. Be careful what you eat.