Transcriptomic and metabolic responses of Calotropis procera to salt and drought stress

Mohammed Z. Mutwakil, Nahid H. Hajrah, Ahmed Atef, Sherif Edris, Mernan J. Sabir, Areej K. Al-Ghamdi, Meshaal J. S. M. Sabir, Charlotte Nelson, Rania M. Makki, Hani M. Ali, Fotouh M. El-Domyati, Abdulrahman S. M. Al-Hajar, Yoann Gloaguen, Hassan S. Al-Zahrani, Jamal S. M. Sabir, Robert K. Jansen, Ahmed Bahieldin, Neil Hall

Calotropis procera is a wild plant species in the family Apocynaceae that is able to grow in harsh, arid and heat stressed conditions. Understanding how this highly adapted plant persists in harsh environments should inform future efforts to improve the hardiness of crop and forage plant species. To study the plant response to droμght and osmotic stress, we treated plants with polyethylene glycol and NaCl and carried out transcriptomic and metabolomics measurements across a time-course of five days. We identified a highly dynamic transcriptional response across the time-course including dramatic changes in inositol signaling, stress response genes and cytokinins. The resulting metabolome changes also involved sharp increases of myo-inositol, a key signaling molecule and elevated amino acid metabolites at later times. The data generated here provide a first glimpse at the expressed genome of C. procera, a plant that is exceptionally well adapted to arid environments. We demonstrate, through transcriptome and metabolome analysis that myo-inositol signaling is strongly induced in response to drought and salt stress and that there is elevation of amino acid concentrations after prolonged osmotic stress. This work should lay the foundations of future studies in adaptation to arid environments.