PLANT RESPONSE TO MAGNESIUM AVAILABILITY: ROOT MORPHOLOGY ADAPTATION AND INVESTIGATION OF A ROLE FOR THE CLOCK

Understanding the dynamical bases of the interaction between the plant mineral nutrition and the circadian clock could contribute to improve crop yield and resistance to adverse conditions, such as mineral element deficiencies. Magnesium is an essential element that catalyzes more than six hundred enzymatic reactions and occupies the center of the chlorophyll structure in plants. Physiological targets of magnesium deficiency are generally better described in aerial than in belowground organs. In this thesis, we first characterized the root morphology of the model species Arabidopsis thaliana (Columbia-0) in response to magnesium supply during in vitro culture. The length of primary root and the number and length of lateral roots decreased during magnesium depletion. A local magnesium-rich source does not enhance the root foraging capacity, unlike some other major nutrients. Auxin and abscisic acid emerged as two hormones shaping root morphology in response to magnesium deficiency. Second, we investigated the natural variation of the root morphology response to magnesium supply in Arabidopsis. Thirty-six accessions were screened in vitro. Compared to the reference Columbia-0, some accessions had higher number and length of lateral roots at low magnesium supply. Root or shoot magnesium concentrations did not implicitly correlate with the root morphological traits. However, shoot calcium and root phosphorus concentrations correlated positively with the lateral root number and length, while root iron negatively with the length of primary root. Third, we focused on the interaction between the plant magnesium nutrition and the circadian clock circuit. We tested for a possible involvement of PHYTOCHROME INTERACTING FACTOR 3-LIKE 1 (PIL1) - a clock-associated gene that is down-regulated during magnesium depletion - in morphological and physiological responses, and for a circadian connection of PIL1 in the context of magnesium deficiency. The phenotypes of loss-of-function and overexpression lines did not reveal a major role of PIL1 in the magnesium deficiency symptom manifestation but rather in the plant mineral profile. The expression of PIL1 was apparently not under any circadian control. However, PIL1 seemed to regulate the expressions of some core clock genes (CCA1, LHY and PRR9), which were also targets during magnesium deficiency. In conclusion, PIL1 has a link with the circadian rhythm machinery but it does not emerge as a pivotal regulator of magnesium stress responses.Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Approaches to the Development of Ecotourism on the Qinghai-Tibet Plateau: The Aim Being Sustainable Growth

The study features the necessity and feasibility of developing ecotourism on the Qinghai-Tibet Plateau and approaches to the region's sustainable growth. The biodiversity, rich natural resources, and distinctive cultural and religious assets that the Qinghai-Tibet Plateau boasts have made tourism greatly beneficial to the local economy, but the growth of tourism in the region has also caused damage to the local environment. The study hence provides solutions to the issue, putting forward plans for the sustainable growth of the Qinghai-Tibet Plateau

Root morphology of Arabidopsis thaliana in response to magnesium supply

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Influence of magnesium sources on root architecture

info:eu-repo/semantics/publishe

Root morphology of Arabidopsis thaliana in response to magnesium supply

info:eu-repo/semantics/publishe

Root morphology in response to magnesium supply.

info:eu-repo/semantics/publishe

Influence of Magnesium Supply on the Root Development of Arabidopsis thaliana

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Root morphology in response to magnesium supply

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An update on magnesium homeostasis mechanisms in plants

Worldwide, nearly two-thirds of the population do not consume the recommended amount of magnesium (Mg) in their diet. Furthermore, low Mg status (hypomagnesaemia) is known to contribute to a number of human chronic disease conditions. Because the principal dietary Mg source is of plant origin, agronomic and genetic biofortification strategies are aimed at improving nutritional Mg content in food crops to overcome this mineral deficiency in humans. This update incorporates the contributions of annotated permeases involved in Mg uptake, storage and recycling with a schematic model of Mg movement at the organ and cellular levels in the model species Arabidopsis thaliana. Furthermore, approaches using mutagenesis or natural ionomic variation to identify loci involved in Mg homeostasis in roots, leaves and seeds will be summarised. A brief overview will be presented on how Arabidopsis research can help to develop strategies for biofortification of crops.info:eu-repo/semantics/publishe

Mg deficiency interacts with the circadian clock and phytochromes pathways in Arabidopsis

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