Thermostability of the PYL-PP2C Heterodimer Is Dependent on Magnesium: In Silico Insights into the Link between Heat Stress Response and Magnesium Deficiency in Plants.

Magnesium deficiency increases the susceptibility of plants toward heat stress. The correlation between magnesium levels and stress response has been studied at the physiological level; albeit, the molecular explanation to this relationship remains elusive. Among diverse pathways implicated in the heat stress, the abscisic acid (ABA) signal modulates the heat stress response by magnesium dependent phosphatases (PP2Cs). Exclusively, sequestration of PP2Cs by ABA receptors (PYLs) in the heterodimer form activates the stress response through ABA responsive transcription factors. In this study, the molecular interplay between magnesium levels and ABA related heat stress response was investigated. Molecular dynamics simulations have been applied to two different PYL-PP2C heterodimer systems representing normal and magnesium deficient conditions. The heterodimer conformation and stability were delineated at high temperatures mimicking heat stress. Results showed that the thermostability of the heat stress response heterodimer was significantly dependent on the magnesium. Furthermore, a conserved aromatic cluster at the dimer interface acted synergistically with the metal to confer thermostability to the heterodimer structure. These structural insights into one of the possible links between magnesium levels and stress highlight the importance of metal micronutrients for tuning the stability of the stress-related proteins and optimizing tolerance.