Project description:Root hairs are frequently reported to be plastic in response to nutrient supply, but relatively little is known about their development in response to magnesium (Mg) availability, and evidence is scarce about the signals involved in this process. Here, we showed that both density and length of root hairs of Arabidopsis decreased logarithmically with increasing Mg supply in the media , which correlated with the initiation of new trichoblast files and likelihood of trichoblasts to form hairs. Low Mg resulted in greater concentrations of reactive oxygen species (ROS) and Ca2+ in the roots and displayed a stronger tip-focused gradient of ROS and cytosolic Ca2+ concentration ([Ca2+]c) during initiation and elongation of root hairs. This gradient could be eliminated by DPI or BAPTA. Application of either DPI or BAPTA to low Mg treatment blocked the enhanced development of root hairs. The opposite was true when the plants under high Mg were supplied with Ca2+ or PMS. Whole-genome transcriptome data revealed that the maximum differential expressed genes involved in ‘stress’, ‘oxidation reduction’, ‘ion transport and homeostasis’ and ‘cell wall organization’. A greater fraction of morphogenetic H-genes and root hair -specific genes as well as genes involved in ‘cell wall structure’ were up-regulated by 7-d treatment of 0.5 μM Mg but down-regulated by 7-d treatment of 10,000 μM Mg. It is concluded that a distinct and previously poorly characterized response of root hair development to Mg availability is presented in Arabidopsis where ROS and Ca2+ are the signaling molecules that control this response.
Project description:Physiological mechanisms involved in root hair development in response to magnesium (Mg) availability are unclear. This study investigated the influence of Mg availability on root hair development in arabidopsis grown in different Mg concentrations ranging from 0.5 μM to 10 mM. After 7-d treatment, root hair development was enhanced in roots exposed to low Mg but was inhibited severely in roots grown in high Mg. Low Mg (0.5 µM) enhanced many genes like LRX1, COW1, EXP7 and ROP2 that control root hair development. Low Mg supply also increased concentrations of total Ca2+ and ROS in roots, but application of either BAPTA or DPI to low Mg treatment blocked the enhanced development of root hairs. The opposite was true when the plants under high Mg (3 mM) were supplied with Ca2+ or PMS. Besides, in roots under low Mg and high Mg, the most significant biological function enrichment were in the ‘oxidation reduction’, ‘cell wall organization’, ‘ion response’. This study demonstrated that Ca2+ and ROS played critically in controlling the Mg-induced development of root hairs. Meanwhile, transcriptome analysis associated with Mg supply contributed to a better understanding of molecular events responsible for sensing Mg status. Roots were sampled from five-week-cultivated Arabidopsis after 7 d treatment of low Mg (supplied with 0.5 μM Mg2+) and high Mg (supplied with 10 mM Mg2+).
Project description:To optimize access to nitrogen under limiting conditions, root systems must continuously sense and respond to local or temporal fluctuations in nitrogen availability. In Arabidopsis thaliana and several other species, external N levels that induce only mild deficiency stimulate the emergence of lateral roots and especially the elongation of primary and lateral roots. However, the identity of the genes involved in this coordination remains still largely elusive. In order to identify novel genes and mechanisms underlying nitrogen-dependent root morphological changes, we investigated time-dependent changes in the root transcriptome of Arabidopsis thaliana plants grown under sufficient nitrogen or under conditions that induced mild nitrogen deficiency.
Project description:To cope with limiting phosphorus (P) availability, plants have evolved a series of mechanisms to recycle internal P sources and to acquire P from the soil. One of these mechanisms is the release of low-molecular weight carboxylates, such as malate, which helps to liberate phosphate desorbed to aluminum and iron oxides. As malate release into the rhizosphere and root apopplast also increases iron availability. To identity genes involved in this interaction, we investigated time-dependent changes in the transcriptome of Arabidopsis thaliana roots exposed to sufficient and deficient phoshate levels .
Project description:Plant roots located in the upper soil layers are prone to experience high temperatures. To gain insight into the effect of high temperature on root development and functioning, we exposed five-day-old Arabidopsis thaliana seedlings grown on agar plates to 30 °C for 48 hours, and compared the gene expression profile in the root tip with that from seedlings that remained at 22 °C.
Project description:ra04-07_pgpr - profiling of the root architecture response to phyllobacterium - Experiment 1 : Which genes are up- or down-regulated in Arabidopsis thaliana cultivated in vitro with increased lateral root development in response to Phyllobacterium STM196 inoculation. Experiment 2 : Which genes are up- or down-regulated during the ISR triggered by a rhizobacteria, in comparison with those affected by a pathogenic interaction. Experiment 3 : which genes are specifically induced or repressed in Arabidopsis thaliana by inoculation of the soil with a PGPR vs a bacteria that has the ability to trigger nodule formation in a Legume. - Seeds of wild-type Arabidopsis thaliana (ecotype Columbia) were surface-sterilized and sawn on agar mineral medium (see below). 4 days after storage in the dark at 4degreeC, seedling were cultivated 6 days in a growth chamber (16 h daily, 20-22degreeC) and then transferred on a fresh agar mineral medium inoculated or not with Phyllobacterium STM196 (2.108 cfu/ml). 6 days later, root and leaves were collected, froze on liquid nitrogen and stored at -80degreeC. Keywords: treated vs untreated comparison