Phosphoproteomic Analysis of Maize Seedlings Provides Insights into the Mechanisms of Heat-Stress Tolerance.

The dramatically high temperatures triggered by global climate change threaten maize growth and yield. In recent years, increasing attention has focused on the impacts of heat injury on maize. However, the molecular mechanisms behind maize's adaptation to heat stress remain largely unexplored. To uncover how plants protect themselves from heat stress, we performed a phosphoproteomic analysis on maize leaves by using multiplex iTRAQ-based quantitative proteomic and LC-MS/MS methods. A total of 1594 phosphopeptides ascribed to 875 proteins were identified. A functional enrichment analysis of the proteins and phosphoproteins revealed that the early thermal responses of maize were associated with translational and post-translational modifications, protein turnover, and chaperone binding in the MAPK pathway. A motif analysis also yielded a significant number of potential MAPK substrates. The functional characterization of the phosphoproteins and pathways identified here will provide new insights for improving crop thermal tolerance.