COMT and infection: Proteomic analysis showed that the expression of caffeic acid methyltransferase (COMT), which is one of the key genes regulating lignin synthesis [74], was increased in the barley roots under the compost treatment, suggesting that the compost application may increase the lignin content of cell wall biomass, which could lead to accelerated root growth rates, tolerance of environmental stresses, as well as resistance to pathogen infection.