Combined Fusarium Crown Rot and Drought Stress Leads to Overlapping and Unique Proteomic Responses in Wheat

Fusarium crown rot (FCR) is a soilborne disease that occurs in many cereal-growing regions in the world. An association between FCR development and drought stress has long been known. The FCR symptoms are pronounced under drought stress in both fields and controlled environments. However, the molecular mechanisms involved in the association between drought and FCR remain largely unknown. For the first time, in this study, the proteomic characteristics of wheat plants under FCR, drought (induced by water limitation), and combined stress of FCR and drought were investigated and compared using label-free quantitative proteomic analysis. Significant interactions between FCR and drought were observed. Combined stress of FCR and drought had more detrimental effects on wheat growth compared with each single stress alone. A total of 823 (FCR), 414 (drought), and 1,520 (combined stress) proteins that responded to three stress conditions were identified, respectively. In addition to proteins, biological processes and KEGG pathways unique to single stress and that were shared among all three stress conditions were also identified. Some of the overlapping proteins, such as chitinase and glutathione S-transferase, may contribute to maintaining basic FCR resistance under drought in adult wheat plants. Moreover, combined proteomic and metabolic analysis indicated that the increased sugar content and reduced lignin content may contribute to the increased FCR severity under combined stress. This study provides insights into the complex interactions between FCR and drought at the proteomics level and will guide future efforts for the genetic improvement of FCR resistance under drought.