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New DELLA-based biotechnological tools for sustainable Agriculture

Periodic Reporting for period 1 - DELLATECH (New DELLA-based biotechnological tools for sustainable Agriculture)

Reporting period: 2017-04-01 to 2019-03-31

The consequences of climate change, population growth and reduction of arable land are strongly compromising food security. Therefore, there is an urgent need to find novel crop varieties with high yield under sub-optimal growing conditions. As sessile organisms, plants have to cope ‘in situ’ with environmental fluctuations in order to survive and achieve reproductive success. For this, plants constantly monitor the environment and transmit this information to DELLA proteins that orchestrate the response to hazardous conditions by favouring the defence mechanisms and decreasing growth rates. Because of their broad involvement in the regulation of plant life, DELLAs have classically been a favourite target in agriculture. For example, semi-dwarf cereal varieties with enhanced DELLA activity were on the basis of the green revolution that averted a food security crisis in the 1960s-70s. These varieties showed improved harvest index, decreased lodging and enhanced resistance to fungal infections. However, modification of DELLA function has other pleiotropic and undesired effects. Moreover, from an agronomical point of view, DELLA-mediated growth-restrain represents a penalty in productivity and would be desirable to avoid it. The main objective of DELLATECH has been to develop novel DELLA-based biotechnological tools for a more efficient and sustainable agriculture. Specifically, we have addressed this objective with two complementary strategies in the model plant Arabidopsis thaliana: (1) engineering of DELLA proteins (edgetic alleles) where some functions are impaired (for example the inhibition of growth) without affecting others (for example the defence response); and (2) identification of chemical compounds that block specific aspects of DELLA function (edgetic compounds).
The activity of DELLA proteins relies on their capacity to interact with a myriad of transcription factors (i.e. regulators of gene expression) involved in diverse processes. Our work has resulted in: (1) the generation of 4 novel DELLA versions that selectively impair interaction with growth promoting transcription factors but maintain other interactions unaffected, for example with regulators of the defence response; and (2) the identification of 3 compounds that selectively impair DELLA interaction with growth regulators in yeast. This work has been presented in group and departmental seminars and in national and international workshops. Moreover, practical classes and exhibitions on environmental control of plant development were performed in collaboration with the Outreach Committee at the IBMCP.
We have succeeded in the identification of edgetic alleles with a-la-carte modified DELLA activity in Arabidopsis. In this way and given the wide conservation of DELLA function, we are providing novel biotechnological tools to scalpel plant growth and defence responses that will be tested in crops such as tomato and rice. On the other hand, we have also identified a number of chemical compounds that impair certain DELLA interactions in a heterologous system (yeast). Although field tests have not been carried out yet, this strategy has the advantage that modification of genetic resources is not required, saving time and overriding social concerns with the use of genetically modified organisms.
Representative inflorescences of a wild-type Arabidopsis plant (left) and a gai-1D mutant (right), w