It's not clear-cut how a plant determines enough is enough and stops making roots. New research from Washington University in St. Louis identifies a cellular transporter that links two of the most powerful hormones in plant development -- auxin and cytokinin -- and shows how they are involved in putting the brakes on root initiation and progression. The new work by Lucia Strader, associate professor of biology in Arts & Sciences, and her co-authors is published July 18 in the journal Developmental Cell.
"This is exciting because for a long time, we've known that auxin and cytokinin have opposing roles, but the direct links between how one of them might affect the other in lateral root production was not well understood," Strader said.
Roots - Roots - Fingers - Side - Majority
Lateral roots are the roots that branch out horizontally like fingers stretching out to the side. They make up the majority of root mass.
"Our data suggests that one of the ways that cytokinin can decrease lateral root production is by increasing the levels of this transporter to limit contributions of this particular auxin precursor to active auxin," she said.
Plant - Hormone - Auxin - Aspect - Plant
The plant hormone auxin controls almost every aspect of plant growth and development, including stimulating root growth overall. Previous research has shown that another important hormone called cytokinin has a limiting effect -- controlling the locations where new lateral roots could possibly sprout, and ensuring sufficient spacing between neighboring roots.
Until now, however, scientists have not identified how these hormones "talk" to each other.
Model - Plant - Arabidopsis - Thaliana - Strader
Working with the model plant Arabidopsis thaliana, Strader decoded a key to this conversation.
Strader discovered that a cellular transporter she dubbed TOB1 can stash away an auxin precursor by moving it into a vacuole, an organ in the plant cell that acts as a kind of storage space or holding pen. That action prevents the precursor, which is called...
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