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By using primary roots of Arabidopsis thaliana and forefront genetic, imaging and analytical approaches, we are currently asking the following questions:

How is JA-Ile biosynthesis initiated?

Plants are often exposed to injury and serve as hosts for a variety of pests and pathogens. Therefore, they require mechanisms to detect the occurring damage, inform the host about tissue disruption, and initiate processes aimed at restoring homeostasis. A variety of damage signals can inform the plant about the occurrence of lesions, including chemical and physical ones. The jasmonate pathway is a key regulator of plant defense responses. In spite of its importance, it still unknown what molecular mechanisms trigger JA-Ile production. We have recently isolated novel mutants, which are now being characterized to identify those sensing mechanisms. In addition, we are quantifying the stimulus needed to activate intracellular JA signaling with a mechanistic approach.

How do JA-Ile precursors translocate?

Multicellular organisms rely upon the movement of signal molecules across cells, tissues and organs to communicate among distal sites. In plants, the translocation of phytohormones occurs through different transport pathways and ensures effective spatial and temporal coordination of growth and development in response to internal and environmental cues. For instance, localized tissue damage induces both proximal and distal defense responses, through several long-distance signaling mechanisms that have started to emerge only recently. By coupling grafting experiments to hormone profiling, we have found that wound-induced JA-Ile precursors generated in shoots translocate to undamaged roots through the phloem. Their relocation is essential to activate adaptive growth and defense responses in below-ground organs. We are now aiming to identify the molecular mechanisms of their transport.

What are the cellular specificities in JA-Ile responses?

The activation of JA-Ile-mediated defense is costly and often accompanied by significant growth inhibition. To therefore effectively coordinate growth-defense trade-offs in both space and time, JA-Ile signaling mediated by MYC transcription factors (chiefly MYC2, MYC3 and MYC4) is normally kept repressed by a modular repressor complex of JAZ, NINJA and TPL proteins. The presence of several MYCs and 13 JAZ genes in Arabidopsis, some of which are subjected to alternative splicing, suggests that there is large diversity in small molecule recognition and signaling in different tissues and cell-types. We are currently investigating those cellular specificities in JA-Ile-regulated responses.

This page was last modified on 30.10.2019.

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