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A direct, multi-faceted approach to investigate plant hormones spatial regulation: the case of gibberellins

Periodic Reporting for period 3 - GAtransport (A direct, multi-faceted approach to investigate plant hormones spatial regulation: the case of gibberellins)

Reporting period: 2019-02-01 to 2020-07-31

Plant hormones are small signaling molecules that direct key processes in plants’ development and adaptive growth, including in crop species. For example, during the so-called 'green revolution', high-yielding cultivars of maize, wheat, and rice, which revolutionized these grains world productivity, were identified as mutants in biosynthesis or signaling of the plant hormone gibberellin. Thus, understanding the details of gibberellins dynamics in plants has significant research importance with potential practical implications on agriculture, food security and human health. To date, very little information exists on how plants regulate the movement of gibberellins to insure their arrival in the right place, time and concentration so that proper growth and development can be achieved.
The overall goal of the proposed research is to elucidate and characterize GA flow in plants and identify the mechanisms controlling it. The specific objectives of this research are:
1. To provide a comprehensive spatial map of gibberellins distributions and accumulation sites.
2. To elucidate gibberellins flow pathways and quantify their kinetics.
3. To identify and characterize the mechanistic components governing gibberellins flow and accumulation.
To address the first objective, we developed gibberellins tagged with a fluorescent marker that enable their visualization in plants via microscopy. We’re currently applying these tagged derivatives to different plant species to uncover the distribution patterns and accumulation sites of gibberellins in each plant. To address the second objective, we’re developing two platform that will enable to generate gibberellins in a known location in the plant and in a defined time so that their movement thereof could be studied and quantified. The first platform, which utilize light to generate gibberellins, is now established in its first version. This platform was used to generate gibberellins in different locations in plant roots and quantify parameters of their movement (publication of these results is now in process). We’re currently working on developing a second generation of the platform as well as utilizing the existing one to extract more information on gibberellins flow. To address the third objective, we’re using two approaches to screen for proteins that regulate gibberellins flow. In the first, we used the fluorescently tagged gibberellins to identify one protein transporter of gibberellins in plants. The identified transporter was studied and a report on its discovery and characterization is now published. In the second, we’re using chemical techniques to identify such proteins. The required molecules and assays to implement this approach are now established and ready for use.
This project is expected to accomplish: 1) map the accumulation sites of bioactive gibberellins and their immediate precursors in Arabidopsis thaliana and identify sites where they play a functional role. 2) Define and quantitate gibberellins flow pathways in Arabidopsis thaliana roots. 3) Identify novel gibberellin transporters and novel gibberellin-binding proteins. 4) Establish innovative techniques to explore gibberellins mobility in Arabidopsis and in additional plant species.