Salt stress is a severe environmental factor that detrimentally affects wheat growth and production worldwide. Previous studies illustrate that exogenous jasmonic acid (JA) significantly improved salt tolerance in plants. However, little is known about the underlying molecular mechanisms of JA induced physiochemical changes in wheat seedlings under salt stress conditions. In this study, biophysiochemical and transcriptome analysis was conducted to explore the mechanisms of exogenous JA induced salt tolerance in wheat. Exogenous JA increased salt tolerance of wheat seedlings by alleviating membrane lipid oxidation, improving root morphology, enhancing the contents of ABA, JA and SA and increasing relative water content. In the RNA-seq profiles, we identified a total of 54,263 unigenes and 1,407 unigenes showed differentially expressed patterns in JA pretreated wheat seedlings exposed to salt stress comparing to those with salt stress alone. Subsequently, gene ontology (GO) and KEGG pathway enrichment analysis characterized that DEGs involved in linoleic acid metabolism and plant hormone signal transduction pathways were up-regulated predominantly in JA pretreated wheat seedlings exposed to salt stress. We noticed that genes that involved in antioxidative defense system and that encoding transcription factors were mainly up- or down-regulated. Moreover, SOD, POD, CAT and APX activities were increased in JA pretreated wheat seedlings exposed to salt stress, which is in accordance with the transcript profiles of the relevant genes. Taken together, our results demonstrate that the genes and enzymes involved in physiological and biochemical processes of antioxidant system, plant hormones and transcriptional regulation contributed to JA-mediated enhancement of salt tolerance in wheat. These findings will facilitate the elucidation of the potential molecular mechanisms associated with JA-dependent amelioration of salt stress in wheat and lay theoretical foundations for future studies concerning the improvement of plant tolerance to abiotic environmental stresses.

Simplicillium spp. are mycoparasites that exert growth-inhibitory effects on phytopathogenic fungi. However, limited studies have examined the effects of Simplicillium spp. on powdery mildews. In this study, morphological and molecular analyses revealed that S. aogashimaense is a mycoparasite of the wheat powdery mildew fungus, Blumeria graminis f. sp. tritici (Bgt), under field conditions. The inoculation of Bgt colonies with S. aogashimaense significantly impaired Bgt colony formation and conidial distribution and markedly decreased the biomass of Bgt. To examine the interaction between Simplicillium and Bgt, an S. aogashimaense strain that constitutively expresses green fluorescent protein (GFP) was constructed using the Agrobacterium tumefaciens-mediated transformation (ATMT) method. The hyphae of GFP-expressing S. aogashimaense directly penetrated the B. graminis structures. These findings indicate that ATMT can be employed to reveal the biocontrol activities of physiologically and phylogenetically diverse Simplicillium spp. In vitro, S. aogashimaense exudates compromised Bgt conidial germination and appressorial formation. Thus, S. aogashimaense functions as a potential biological control agent by impeding the development of Bgt and can be a viable alternative for controlling the wheat powdery mildew. To gain further insights into the mechanism underlying this mycoparasitism, the genome of S. aogashimaense was sequenced and assembled. S. aogashimaense harbored seven chromosomes comprising 8963 protein-coding genes. Additionally, two putative effector-coding genes (Sao008714 and Sao006491) were identified. The expression levels of Sao008714 and Sao006491 in S. aogashimaense were dramatically upregulated during the mycoparasitic interaction. In addition, 41 gene clusters putatively involved in the production of secondary metabolites, which exhibit insecticidal, antifungal and antibacterial activities, were identified using genome-wide identification, annotation and analysis of secondary metabolite biosynthesis gene clusters. These results suggest that S. aogashimaense parasitizes Bgt and hence, can be considered for phytopathogen management.

Trichothecium roseum is known to be a mycoparasite and inhibit phytopathogenic fungi. However, so far, only scarce information is available on the impacts of T. roseum on powdery mildews. Based on the morphological and molecular analysis, we identified T. roseum as a mycoparasite on colonies of the wheat powdery mildew fungus (Blumeria graminis f. sp. tritici, Bgt, recently clarified as B. graminis s. str.) and then showed that T. roseum was capable of efficiently impairing colony formation and conidial distribution of Bgt. After inoculation of T. roseum conidia on Bgt colonies, the biomasses of Bgt significantly decreased 1.46, 1.64, 7.55, and 10.49 times at 2, 4, 6, and 8 dpi, respectively. Thus, T. roseum, acting as a potential biological agent, impeded the developments of Bgt, making it a viable alternative for wheat powdery mildew control. Utilizing the Agrobacterium tumefaciens-mediated transformation (ATMT) system, a T. roseum strain that constitutively expressed green fluorescent protein was produced to improve the visualization of the T. roseum-Bgt interaction and showed direct hyphae interaction of T. roseum with Bgt structures during parasitic processes. These findings indicate that ATMT is a potent and efficient method for transforming T. roseum. Nevertheless, our results suggest that T. roseum is an antagonistic parasite of the wheat powdery mildew fungus, and hence, can be considered for phytopathogen management.