Structural and mechanistic analysis of engineered trichodiene synthase enzymes from <i>Trichoderma harzianum</i>: towards higher catalytic activities empowering sustainable agriculture

<p><i>Trichoderma</i> spp<i>.</i> are well-known bioagents for the plant growth promotion and pathogen suppression. The beneficial activities of the fungus <i>Trichoderma</i> spp<i>.</i> are attributed to their ability to produce and secrete certain secondary metabolites such as trichodermin that belongs to trichothecene family of molecules. The initial steps of trichodermin biosynthetic pathway in <i>Trichoderma</i> are similar to the trichothecenes from <i>Fusarium sporotrichioides</i>. Trichodiene synthase (TS) encoded by <i>tri5</i> gene in <i>Trichoderma</i> catalyses the conversion of farnesyl pyrophosphate to trichodiene as reported earlier. In this study, we have carried out a comprehensive comparative sequence and structural analysis of the TS, which revealed the conserved residues involved in catalytic activity of the protein. <i>In silico</i>, modelled tertiary structure of TS protein showed stable structural behaviour during simulations. Two single-substitution mutants, i.e. D109E, D248Y and one double-substitution mutant (D109E and D248Y) of TS with potentially higher activities are screened out. The mutant proteins showed more stability than the wild type, an increased number of electrostatic interactions and better binding energies with the ligand, which further elucidates the amino acid residues involved in the reaction mechanism. These results will lead to devise strategies for higher TS activity to ultimately enhance the trichodermin production by <i>Trichoderma</i> spp. for its better exploitation in the sustainable agricultural practices.</p

Hopanoid lipids: from membranes to plant–bacteria interactions

International audienceLipid research represents a frontier for microbiology, as showcased by hopanoid lipids. Hopanoids, which resemble sterols and are found in the membranes of diverse bacteria, have left an extensive molecular fossil record. They were first discovered by petroleum geologists. Today, hopanoid-producing bacteria remain abundant in various ecosystems, such as the rhizosphere. Recently, great progress has been made in our understanding of hopanoid biosynthesis, facilitated in part by technical advances in lipid identification and quantification. A variety of genetically tractable, hopanoid-producing bacteria have been cultured, and tools to manipulate hopanoid biosynthesis and detect hopanoids are improving. However, we still have much to learn regarding how hopanoid production is regulated, how hopanoids act biophysically and biochemically, and how their production affects bacterial interactions with other organisms, such as plants. The study of hopanoids thus offers rich opportunities for discovery