TITLE of the PhD project: Study of the contribution of potassium to the osmoregulatory mechanism of bulliform cells in rice;

Place of training: Institut Agro Montpellier, University of Montpellier, Montpellier, France.

PhD supervisor : Prof. Pierre BERTHOMIEU pierre.berthomieu@supagro.fr  (+33) 499613130

The project will be developed in the general context of transitions of agricultural systems towards agroecology. It more specifically addresses issues related to climate change mitigation. Leaf curl in cereals is observed, for example, in situations of water stress or high temperature, with a response that is dynamic and reversible depending on the intensity and duration of these constraints.

Leaf rolling is an indicator that the plant perceives the constraint and as such is a means of evaluating the sensitivity of a variety to drought or high temperatures. The question is whether “controlling” leaf curl in varieties bred for it, for example to make it more responsive to changes in the environment, might allow such varieties to better tolerate stress.

Osmocontractility of the bulliform cells present on the adaxial epidermis appears to be the driving force behind leaf curling/uncurling. However, although many leaf curl mutants have been described, the mechanisms responsible for bulliform cell volume variations remain unknown.

In the proposed work, the starting hypothesis is that bulliform cells may function similarly to guard cells that control stomatal opening based on their osmotic status, which in turn depends on ionic and solute transport. We will use this model to see what is conserved or different in the bulliform cell.

The work will be done on rice. A list of genes involved in the opening or closing of stomata has been established, and the expression of orthologs/paralogs in bulliform cells has been defined. On this basis, rice KO mutants are, and will be, made using the CRISPR-Cas9 technique. For example, we already have a quadruple mutant showing altered curling ability.

The mutants showing alterations in leaf curling will be studied at the phenotypic and molecular levels to better characterize the mechanism underlying this alteration. In particular, to study the impact of possible alterations in K+ transport, electrophysiology experiments could be performed in planta.

The subject is a typical molecular physiology subject. Different techniques should be used, namely gene expression analyses, the realization of genetic constructs for CRISPR-Cas9 genome editing in rice, cloning and functional characterization of ion transporters in heterologous systems (yeast, electrophysiology), physiological measurements, in particular of leaf curling, under controlled conditions…

The project is co-financed for 3 years by the Institut Agro Montpellier and the Occitanie region, and could start on October or November 1, 2023. The position is open to any candidate holding a Master’s Degree in plant molecular physiology or equivalent.

For more information & Application: Contact Prof. Pierre BERTHOMIEU pierre.berthomieu@supagro.fr  and to apply, send a CV, a letter of motivation as well as short summaries of all previous research experiences. Application deadline is August 31st, 2023, but applications will be examined on a first-come, first-served basis and the position should be filled before the application deadline.

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