Dec. 20, 2009 Auxin, the jack-of-all-trades among plant hormones, has the 'auxin response factors' (ARFs) to thank for its multi-talented nature. One of the actions of these ARFs is to prevent a non-embryonic cell from changing into an embryonic cell. Dutch researcher Eike Rademacher has shown that without ARFs, a cell like this can actually form the basis for a new embryo.
The plant hormone auxin is a veritable jack-of-all-trades: it allows plants to grow, provides roots and makes sure that the stems grow up and the roots grow down. It's also the only hormone with a complex network of transporters at its beck and call, allowing it to go to work anywhere in the plant. But the question of how auxin gives cell-specific instructions for change had remained largely unanswered until now.
Delivering the right message Eike Rademacher, a researcher within the Vidi project of Dolf Weijers, has now discovered how cells actually find out what auxin has planned for them. It happens via the auxin response factors (ARFs), which transfer the auxin message.
Rademacher investigated how auxin directs the characteristics of different cells in a plant embryo. He examined a large number of different cells in which the 23 existing ARFs were connected. By deliberately disconnecting the ARFs in cells, he discovered that virtually every step of a plant's embryonic development was influenced by auxin.
Rademacher established that there are 6 ARFs which act to prevent non-embryonic cells from transforming into embryonic cells. When these six factors are disconnected, non-embryonic cells change into embryo cells, so that two embryos can develop in a single seed. Rademacher swapped ARFs from different cells with each other and observed that the identity of the ARF plays a significant role in the correct response to auxin. A matter of interpretation
Eike Rademacher's findings also offer an explanation for the versatility of auxin. Since different ARFs are active in every cell, each with its own characteristics, the auxin message is translated differently in each cell. The message is always the same, but one cell will hear 'turn into a root' and the other will hear ' turn into a leaf'. The endless combinations of ARFs probably explain why auxin can play so many different roles.
Eike Rademacher's research is part of the project of Vidi winner Dolf Weijers. Weijers is investigating how cell identity is established, as well as communication between cells in plant embryos.
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The above story is based on materials provided by NWO (Netherlands Organization for Scientific Research).
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