Genome mining and biosynthesis of a polyketide from a biofertilizer fungus that can facilitate reductive iron assimilation in plant

Abstract

Fungi have the potential to produce a large repertoire of bioactive molecules, many of which can affect the growth and development of plants. Genomic survey of sequenced biofertilizer fungi showed many secondary metabolite gene clusters are anchored by iterative polyketide synthases (IPKSs), which are multidomain enzymes noted for generating diverse small molecules. Focusing on the biofertilizerTrichoderma harzianumt-22, we identified and characterized a cryptic IPKS-containing cluster that synthesizes tricholignan A, a redox-activeortho-hydroquinone. Tricholignan A is shown to reduce Fe(III) and may play a role in promoting plant growth under iron-deficient conditions. The construction of tricholignan by a pair of collaborating IPKSs was investigated using heterologous reconstitution and biochemical studies. A regioselective methylation step is shown to be a key step in formation of theortho-hydroquinone. The responsible methyltransferase (MT) is fused with an N-terminal pseudo-acyl carrier protein (ψACP), in which theapostate of the ACP is essential for methylation of the growing polyketide chain. The ψACP is proposed to bind to the IPKS and enable thetransMT to access the growing polyketide. Our studies show that a genome-driven approach to discovering bioactive natural products from biofertilizer fungi can lead to unique compounds and biosynthetic knowledge.

Effect of Colonization of Trichoderma harzianum on Growth Development and CBD Content of Hemp (Cannabis sativa L.)

“…We propose that the root colonization by Trichoderma harzianum entrains a sequence of biochemical processes which amplify the polyketide and the plastidial DOXP/MEP pathways for cannabinoid production such as THC and CBD, which has been recently presented by Lowe et al [ 76 ]. This hypothesis is underpinned by the well-known production of multiple volatile organic compounds by Trichoderma species that promote the plant growth of plants [ 77 ] and the secretion of small molecules, such as polyketides, observed in Trichoderma harzianum T-22 [ 78 ]. Moreover, a second indirect pathway that might be beneficial for CBD content increase is the enhancement of phosphorus availability [ 79 ].…”

Effects of Foliar Treatment with a Trichoderma Plant Biostimulant Consortium on Passiflora caerulea L. Yield and Quality

“…Plant-beneficial fungi from the Hypocrea/Trichoderma genera are among the most widespread microorganisms used in agriculture [1]. Selected and highly active strains are applied as seed [2], soil [3], and foliar treatments [4], and they are largely used as bio/myco-fungicides [5,6], plant biostimulants [7], and biofertilizers [5,8]. The multifaceted actions of plant-beneficial Trichoderma strains are determined by several mechanisms, which are mainly related to antagonism against plant pathogens [9] or activation of plant defence [10].…”

“…The application of Trichoderma strains increases plant photosynthetic ability, up-regulating both light harvesting components and Calvin cycle (dark reaction) components [24]. Trichoderma and its secondary metabolites also enhance the uptake and use efficiency of macronutrients, such as nitrogen [3,16] or phosphorus [25,26], and oligo/micro-nutrients, such as iron [8,27,28] or zinc [29].…”

One Polyketide Synthase, Two Distinct Products: Trans‐Acting Enzyme‐Controlled Product Divergence in Calbistrin Biosynthesis

“…Although trans ‐ERs are widely adopted in the biosynthesis of fungal polyketides and polyketide‐nonribosomal peptide hybrids, trans ‐CMeTs are rarely found in fungal natural product pathways, and have only been discovered in the biosynthesis of a few fungal natural products, including pseurotin [11a] and tricholignan A [21] . To clarify the function of this unusual methyltransferase CalH′, we first performed in vitro enzymatic reactions of the PKS CalA′ and the acyltransferase CalD′′ in the absence of CalH′.…”

“…Although trans-ERs are widely adopted in the biosynthesis of fungal polyketides and polyketide-nonribosomal peptide hybrids, trans-CMeTs are rarely found in fungal natural product pathways,a nd have only been discovered in the biosynthesis of af ew fungal natural products,i ncluding pseurotin [11a] and tricholignan A. [21] To clarify the function of this unusual methyltransferase CalH',w ef irst performed in vitro enzymatic reactions of the PKS CalA' and the acyltransferase CalD'' in the absence of CalH'.A ss een in the in vivo experiments, 11 and 12,the unmethylated analogues of 9 and 10,r espectively,w ere produced ( Figure 5A), suggesting that the methylation by CalH' does not affect the CalDcatalyzed transacylation. Meanwhile,t he in vitro enzymatic reaction of CalH' with partially purified 11 did not yield the methylated product ( Figure 5B,t races ia nd ii).…”