Pilzgenomik und -biologie
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A Group of Aminotransferase Domain-Containing Proteins in Trichoderma harzianum Resembles Enzymes Catalyzing Acc Synthesis

Luis David Maldonado-Bonill

Production of phytohormones by plant-interacting Trichoderma species modifies the plant physiology to allow its colonization, and to promote plant growth and defense. Ethylene-dependent responses are triggered in plants inoculated with Trichoderma spp., but it is unclear whether such response is triggered by ethylene produced by Trichoderma itself. The rate-limiting step in ethylene biosynthesis is catalyzed by the enzyme 1-Aminocyclopropane- 1-Carboxylic Acid (ACC) Synthase (ACS). To gain insight into ethylene production in Trichoderma spp., the polypeptide sequences of six ACS-like proteins were identified in the endophytic T. harzianum. The identified ACS- like proteins have features of PLP-dependent enzymes and five of them conserve most of residues necessary to catalyze the biosynthesis of ACC. The predicted structure of ThACS-like1 illustrates a folding reminiscent of the apple enzyme MdACS1 and supports its ACS activity. An inspection into Trichoderma genomes confirmed that ACS- like1 is conserved in the unrelated species T. harzianum, T. atroviride, and T. reesei, although T. harzianum is enriched in ACS-like genes. These results demonstrate that T. harzianum, T. atroviride, and T. reesei might be endowed to synthesize ACC as a critical step to produce ethylene during their interaction with plants.