6533b82afe1ef96bd128c8cf

RESEARCH PRODUCT

Ecophysiological and molecular processes involved in water stress memory in pea: from gene expression regulation to plant hydromineral nutrition

subject

description

Climate change induces increasingly frequent periods of water deficits during the crop cycle. These periods of water stress negatively impact the plant, notably by limiting the availability of resources (water, mineral elements) and by limiting carbon fixation by the plant. In this context, several studies highlighted the beneficial effect of “priming” of a first stress on the response to a second stress by the induction of a transcriptional memory. This memory depends on epigenetic modifications implemented during the first stress. These modifications can regulate the expression of genes known as “memory genes” which have been characterized in the aerial parts of Arabidospsis and maize. However, little is known about the effect of water stress memory on the different physiological processes of the plant. During our study we wanted to highlight the memory of the plant at various levels ranging from the expression of genes to the physiological traits of plant. We chose to conduct our study on the pea (Pisum sativum L.) plants, and more particularly its root system, as this crop presents many agro-ecological and nutritional interests. First, we characterized the effect of 13 elementary deficiencies (N, Mg, P, S, K, Ca, B, Mn, Fe, Ni, Cu, Zn, Mo) on the ionome of the pea, from the organ to the plant scale. This allowed us to obtain a specific ionomic signature of each deficiency at different levels. Secondly, we wanted to characterize the potential beneficial effect of memory during recurrent water stress. For this we characterized the "memory genes" within the root system, and more precisely within the roots. Then we highlighted the metabolites whose accumulation was specifically regulated during water stress, which could result from the regulation of "memory genes". And finally, we were able to characterize the impact of recurrent water stress on the physiological processes related to plant hydro-mineral nutrition. Our study revealed that a transcriptional memory was established in pea roots, via the regulation of genes involved in epigenetic marks. In addition, three antioxidants were specifically accumulated in roots during recurrent water stress: mannitol-1-phosphate, 3,4-dihydrobenzoic acid and isorhamnetin. At the same time, during the reproductive stage, the accumulation of ABA and cGMP within the roots could be involved in the tolerance of water stress via the induction of stomatal closure. During this period of stress, the accumulation of asparagine could be involved in a better maintenance of plant nitrogen status. Thanks to the ionomic signatures of deficiencies, we were able to highlight the establishment of a Mo deficiency regardless of the type of stress applied. This suggests that a supplementation in Mo during pea growth cycle could be beneficial to reduce the negative impact of water stress. And finally, we were able to put forward an “ecophysiological imprint” of the stress involved in the memory of stress in pea: the increase of nodulation initiation during rewatering period. Taken together, these results provide new insights for understanding water stress memory in pea plants and offer new insights into the resilience of pea to recurrent water stress events: on the one hand to fine-tune fertilization and on the other hand for plant breeding strategies.