Biological complexity: plants stress controls (Introduction)

by David Turell , Sunday, April 21, 2019, 17:57 (1832 days ago) @ David Turell

Using RNA alterations chloroplasts are changed in stress situations:

https://phys.org/news/2019-04-scientists-uncover-link-rna-chloroplast-to-nucleus.html

"How will plants fare in more extreme weather conditions? When experiencing stress or damage from various sources, plants use chloroplast-to-nucleus communication to regulate gene expression and help them cope.

"Now, Salk Institute researchers have found that GUN1—a gene that integrates numerous chloroplast-to-nucleus retrograde signaling pathways—also plays an important role in how proteins are made in damaged chloroplasts, which provides a new insight into how plants respond to stress.

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"In plant cells, structures called chloroplasts convert energy from sunlight into chemical energy (photosynthesis). Normally, the nucleus of the cell transmits information to the chloroplasts to maintain steady energy production. However, in a stressful environment, chloroplasts send an alarm back to the cell nucleus using retrograde signaling (creating a chloroplast-to-nucleus communication feedback loop). This SOS prompts a response that helps regulate gene expression in the chloroplasts and the nucleus to optimize energy production from sunlight.

"Previously, the Chory lab identified a group of genes, including GUN1, that influence other genes' expression in the cell when the plant experiences stress. GUN1 accumulates under stressful conditions but the exact molecular function of GUN1 has been difficult to decipher, until now.

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"In plants without GUN1, gene expression changed, as did RNA editing in chloroplasts. (RNA editing is a modification of the RNA that changes the identity of nucleotides, so that the information in the mature RNA differs from that defined in the genome, altering the instructions for making proteins.) Some areas of RNA had more editing and other locations had less editing—suggesting that GUN1 plays a role in regulating chloroplast RNA editing.

"After further analysis, the team unexpectedly found that GUN1 partners with another protein, MORF2 (an essential component of the plant RNA editing complex), to affect the efficiency of RNA editing during chloroplast-to-nucleus communication in damaged chloroplasts. Greater activity of MORF2 led to widespread editing changes as well as defects in chloroplast and leaf development even under normal growth conditions (see image). During periods of stress and injury, MORF2 overproduction also led to disruption of chloroplast-to-nucleus communication.

"'Taken together, these findings suggest a possible link between chloroplast-to-nucleus communication and chloroplast RNA editing, which are important regulatory functions for flowering plants, especially during stress," says Chory, Howard Hughes Medical Institute investigator."

Comment: This type of complex series of reactions cannot be developed step by step. It must be designed all at once.