[ad_1]
There is no organic system in the body that does as much for humans as roots for plants. Part of the anchor and one of the mouth, the architecture of the root system of a plant is essential to its success. But the process of growing new roots is expensive for a plant and yields may decrease.
It is not easy to determine how a plant determines that it is enough and stops taking roots. A new study from the University of Washington in St. Louis identified a cell transporter that links two of the most powerful hormones in plant development – auxin and cytokinin – and shows how they intervene in the fight against initiation. and the progression of the roots. The new work of Lucia Strader, badociate professor of biology of arts and sciences, and her co-authors is published July 18 in the journal Developmental cell.
"It's exciting because we've known for a long time that auxin and cytokinin have opposite roles, but the direct links between how one could affect the other in the production of lateral roots have not been well understood, "said Strader.
The lateral roots are roots that branch horizontally like fingers that extend to the side. They constitute the majority of the root mbad.
"Our data suggest that one of the ways in which cytokinin can reduce the production of lateral roots is to increase the levels of this transporter to limit the contributions of this auxin precursor to it. auxin active, "she said.
Pump and release the brakes
The auxin plant hormone controls almost every aspect of plant growth and development, including the stimulation of root growth in general. Previous research has shown that another important hormone called cytokinin has a limiting effect: it controls the locations where new lateral roots might eventually germinate and ensures sufficient spacing between neighboring roots.
Until now, however, scientists have not identified how these hormones "talk to each other".
Work with the model factory Arabidopsis thalianaStrader decoded the key to this conversation.
Strader discovered that a cellular transporter, dubbed TOB1, may contain an auxin precursor by moving it into a vacuole, an organ of the plant cell serving as a sort of storage space or pen . This action prevents the precursor, called IBA, from metabolizing to auxin in its own right – with all its root promotion capabilities.
"If TOB1 is the brake, cytokinin is stepping on the brake," said Strader. "It's the thing that says how much TOB1 should be around to curb the production of lateral roots."
Plants can increase or relax the hold as needed. Strader and his team used genetic modification techniques to eliminate the transporter and had dramatic effects on the next generation of plants.
"When you get rid of that carrier, you have about double the number of side roots of the wild type, without sacrificing the depth of the root," said Strader.
Strader also repeated some of his experiments with yeast and frog oocytes (with the help of Wolf B. Frommer of Heinrich Heine University in Düsseldorf, Germany) instead of a plant, and showed that TOB1 was as effective as the carrier for IBA. these systems.
Slow but steady may be better for plants
Strader's research shows how she and her collaborators began with an unbiased genetic screen and eventually identified an essential regulator of an aspect of plant development that is often ignored – a phenomenon that is not easily visible because the roots are underground.
And Arabidopsis the roots are tiny. At two weeks, its leaves are much smaller than a dime and its roots are filiform and transparent. To highlight the process of producing lateral roots, Strader sought the help of Christopher Topp, principal investigator of the Danforth Plant Sciences Center. Topp used a non-destructive technique to capture the first three-dimensional serial images of developing countries. Arabidopsis mid-range plants – a remarkable achievement, given the extensive research conducted on this model plant.
What they discovered is useful because the molecular mechanisms regulating the architecture of the roots have not been sufficiently studied.
Understanding why and how plants make different types of root architectures can help develop plants better suited to different soil conditions and environments. In subsequent work, Strader has already begun to examine how mutants of TOB1 react differently in soils containing different micronutrients.
"When you get rid of your brakes, you just go crazy," said Strader. "At first, it looks like a good agricultural trait. You want all your soil plants to explore more soil for more nutrients, to get more roots in the water.
"But if you never brake, you're wasting your time making more and more of it," she said. "Probably at some point in the plant's life cycle, this slow but steady approach is better than the off-the-go 'side roots everywhere', one."
Funding: This research was funded by the William H. Danforth Scholarly Research Scholarship Program (at SKP), the National Science Foundation (DGE-1143954 at TAE, IIA-1355406 and IOS-1638507 at CNT, MCB-1413254 to WF and IOS -1453750 to LCS), NSF Center for Engineering Mechanobiology (CMMI-1548571 to LCS), National Institutes of Health (R01 GM112898 to LCS), Alexander von Humboldt Chair (to WF) ), Academia Sinica (CHH) and the Taiwan Ministry of Science and Technology (106-2311-B-001-037 -MY3 at CHH).
Source link
