(You can view the abstract of this paper here or read a provisional copy of the complete paper via Ref 1 below.)
What these researchers also did to these geranium plants was to insert another gene that resulted in more long-lived plants.
This gene codes for an enzyme – isopentenyltransferase (ipt) – that catalyzes the synthesis of the plant hormone cytokinin.
Thus, the GM geranium plants produced more cytokinin than the control plants. (Too avoid deleterious effects of the overproduction of cytokinins on plant development, the ipt gene was designed to only be expressed during the onset of senescence.)
The leaves of the GM geraniums stayed greener significantly longer than the control plants, thanks to the increased levels of cytokinin.
Cytokinin: The Plant Anti-Aging Hormone?
One of the well-known effects of cytokinins in many flowering plants tested is that it delays leaf aging, a.k.a., senescence.
Senescence in plants is the genetically-programmed process characterized by the breakdown of chlorophyll, proteins and other macromolecules, a decrease in photosynthetic activity, and eventually cell death.
Although it is not completely known how cytokinins delay senescence in plants, recent findings suggest that it does so by increasing the amount of carbohydrates (sugars) the plant directs to older leaves, thus keeping them more metabolically active.
Cytokinin has several other critical roles in regulating plant development, too complicated to get into here and now, however.
A recent review regarding the mechanisms of cytokinin action is listed as Ref 2 below.
Though access to the complete text is restricted, the publishers have kindly provided a YouTube video by one of the authors, Dr. Jen Sheen, summarizing the review.
1. Begoña G.-S., et al. (2012) “Production of engineered long-life and male sterile Pelargonium plants.” BMC Plant Biology, Published Online: 31 August 2012. (provisional PDF)
2. Hwang,I., J. Sheen, and B. Müller (2012) “Cytokinin Signaling Networks.” Annual Review of Plant Biology, Vol. 63, pp. 353-380. (Abstract)
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