Coordination between cell wall integrity and cell cycle activity in plants

Plant cell walls surround all plant cells and are composed mainly of carbohydrates like cellulose, which provides plant cells with shape and mechanical resistance. Cellulose microfibres, known for their strength comparable to steel, form the backbone of plant fibres, which have clear relevance in daily life, from dietary fibre to textiles. However, plant cell walls also play a pivotal role in developing new strategies to improve crop yield. A key process is the cell wall integrity (CWI) maintenance mechanism, which monitors the functional state of the cell walls and initiates responses to maintain their integrity during growth and in response to stress. Recent findings have revealed that impairments in CWI not only affect the physical structure of the cell wall but also disrupt the cell cycle. For instance, reductions in pectin levels are linked to delays in the G1/S transition, showing that pectin deposition plays a direct role in regulating cell cycle progression. In Arabidopsis mutants with altered pectin and cellulose composition, we observed a consistent delay in the G2/M phase, indicating that cell wall components are crucial for the timely progression of cell division. Intriguingly, certain plants with altered cell walls exhibit enhanced resistance to stress while maintaining or even improving growth, challenging the classical "growth-defence trade-off" theory. For example, our research suggests that modifications in xyloglucan cross-linking enhance cell wall flexibility, allowing plants to sustain growth while activating defence mechanisms in response to biotic stress. These findings suggest that, contrary to previous assumptions, it may be possible to balance growth and defence in plants through targeted manipulation of cell wall composition. Through this project, we aim to uncover how cell wall integrity and cell cycle activity are coordinated, with the goal of redefining the "growth-defence trade-off"."Our research could lead to innovative strategies to enhance crop performance by improving the balance between growth and resistance to stress. These insights could be directly applicable to crop species such as cereals, offering novel ways to address the urgent challenge of boosting agricultural productivity to support the growing global population in a sustainable manner.

Plant cell walls are essential for plant development and survival. As a matter of fact, around 10% of the genes encoded by the model plant Arabidopsis thaliana are involved in cell wall-related processes, highlighting its critical relevance. This importance explains the increasing interest in this research area. However, there is limited understanding of the molecular mechanisms involved in regulating cell wall synthesis, wall modification in response to stress or during development, and coordination with physiological processes. One key element of plasticity appears to be the cell wall integrity (CWI) maintenance mechanism. This mechanism constantly monitors the functional integrity of the wall and initiates adaptive responses to CWI impairment. The host group identified a core set of CWI maintenance components through a phenotypic clustering approach, including receptor kinases, mechano-/osmo-sensitive channels and other signalling components, which are potentially involved in the detection of stimuli indicating alterations in CWI and in coordinating downstream responses. The objective of this project is to understand how the cell cycle is coordinated with CWI. This coordination has been described in other organisms such as yeasts, but not in plants. By understanding this coordination, this project aims to gain insights into the classical "growth-defense trade-off", a term used to describe the situation where plants invest resources in defence mechanisms at the expense of plant growth. We will characterise the impact of different types of cell wall impairment on the cell cycle, and investigate the signalling processes that contribute to this coordination. Additionally, we will identify novel molecular components involved in this process, and establish the impact of disruptions to CWI on plant fitness. Finally, we will identify candidate genes that could form the basis to develop new strategies to improve the performance of food and bioenergy crops.