Genome complexity: how plants control shape (Introduction)

by David Turell , Monday, October 12, 2020, 20:06 (1292 days ago) @ David Turell

The study defines the proteins and genes involved:

https://phys.org/news/2020-10-dueling-proteins.html

"Wagner and her team have been studying two key groups of proteins that influence plant form and timing of developmental transitions. Terminal Flower 1 (TLF1) proteins promote branch formation. When it is repressed, flowers grow. Flowering Locus T (FT) proteins, on the other hand, promote flowering in response to seasonal cues like day length. Strangely enough, the two proteins are almost identical.

"'These two elements have significance galore," Wagner says. "Besides flowering, they're involved in tuberization in potatoes, bulb formation in onions, tendril formation in grapes, growth cessation in trees, lots of things."

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"It was known that TFL1 and FT1 acted in opposing directions, each "tuning" the activity of the other, but the mechanism of their antagonism has remained fuzzy. In part this was because studying them has presented a technical challenge: They are only present in low levels in a limited number of cells.

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"In the current study, to flesh out TFL1 and FT1's molecular mechanism, they first looked to see where TFL1 was found in the nuclei of plant cells, using the model species Arabidopsis thaliana. They found thousands of sites to which it bound, acting through the transcription factor FD, as neither TFL1 nor FT otherwise can bind directly to DNA. The sites to which TFL1 was recruited were consistent with its role in suppressing flowering and in suppressing gene expression.

"The researchers next examined the relationship of both TFL1 and FT with LEAFY, a gene that is known to give rise to flowers. When they mutated the sites where TFL1 regulates the LEAFY gene, LEAFY protein was now found in parts of the plant where TFL1 is present.

"'We also saw something that we didn't expect," Wagner says. "LEAFY was gone from all the regions that should make flowers."

"That suggested to the team that an unknown factor may be activating the LEAFY gene specifically in the flowering portion of plants via the same site through which TFL1 acts. So, they looked to FT, because of its importance in promoting flowering. By experimentally augmenting FT expression, they found that FT, also binding to the FD transcription factor, was required to act upon LEAFY to promote flower formation.

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"They saw that under conditions that would normally induce the plant to flower, plants that still had normal FT failed to. "It was a strong phenotype and made it very clear to us that FT and TFL1 compete for this FD factor binding site," she says."

Comment: Again a very complex system to control various parts if plant shape and function. It requires design