Sucrose-nonfermenting 1 kinase activates histone acetylase GCN5 to promote cellulase production in Trichoderma.

Trichoderma serves as the primary producer of cellulases and hemicellulases in industrial settings as it readily secretes a variety of cellulolytic enzymes. The protein kinase SNF1 (sucrose-nonfermenting 1) can enable cells to adapt to changes in carbon metabolism by phosphorylating key rate-limiting enzymes involved in the maintenance of energy homeostasis and carbon metabolism within cells. Histone acetylation is an important epigenetic regulatory mechanism that influences physiological and biochemical processes. GCN5 is a representative histone acetylase involved in promoter chromatin remodeling and associated transcriptional activation. Here, the TvSNF1 and TvGCN5 genes were identified in Trichoderma viride Tv-1511, which exhibits promising activity with respect to its ability to produce cellulolytic enzymes for biological transformation. The SNF1-mediated activation of the histone acetyltransferase GCN5 was herein found to promote cellulase production in T. viride Tv-1511 via facilitating changes in histone acetylation. These results demonstrated that cellulolytic enzyme activity and the expression of genes encoding cellulases and transcriptional activators were clearly enhanced in T. viride Tv-1511 mutants in which TvSNF1 and TvGCN5 were overexpressed, with concomitant changes in histone H3 acetylation levels associated with these genes. GCN5 was also found to be directly recruited to promoter regions to alter histone acetylation, while SNF1 functioned upstream as a transcriptional activator that promotes GCN5 upregulation at the mRNA and protein levels in the context of cellulase induction in T. viride Tv-1511. These findings underscore the important role that this SNF1-GCN5 cascade plays in regulating cellulase production in T. viride Tv-1511 by promoting altered histone acetylation, offering a theoretical basis for the optimization of T. viride in the context of industrial cellulolytic enzyme production. KEY POINTS: • SNF1 kinase and GCN5 acetylase promoted cellulase production in Trichoderma by increasing the expression of genes encoding cellulases and transcriptional activators • SNF1 and GCN5 promoted cellulase production by driving H3ac modifications, and GCN5 directly band to the promoter regions to catalyze distinct H3ac modifications • SNF1 acts upstream of GCN5 as a transcriptional activator in the cellulase production of Trichoderma.

Enhanced resistance to heat and fungal infection in transgenic Trichoderma via over-expressing the HSP70 gene.

Heat stress is one of the major abiotic stresses affecting the growth, sporulation, colonization and survival of Trichoderma viride. This study aimed to gain a better insight into the underlying mechanism governing the heat stress response of T. viride Tv-1511. We analysed the transcriptomic changes of Tv-1511 under normal and heat stress conditions using RNA sequencing. We observed that Tv-1511 regulates the biosynthesis of secondary metabolites through a complex network of signalling pathways. Additionally, it significantly activates the anti-oxidant defence system, heat shock proteins and stress-response-related transcription factors in response to heat stress. TvHSP70 was identified as a key gene, and transgenic Tv-1511 overexpressing TvHSP70 (TvHSP70-OE) was generated. We conducted an integrated morphological, physiological and molecular analyses of the TvHSP70-OE and wild-type strains. We observed that TvHSP70 over-expression significantly triggered the growth, anti-oxidant capacity, anti-fungal activity and growth-promoting ability of Tv-1511. Regarding anti-oxidant capacity, TvHSP70 primarily up-regulated genes involved in enzymatic and non-enzymatic anti-oxidant systems. In terms of anti-fungal activity, TvHSP70 primarily activated genes involved in the synthesis of enediyne, anti-fungal and aminoglycoside antibiotics. This study provides a comparative analysis of the functional significance and molecular mechanisms of HSP70 in Trichoderma. These findings provide a valuable foundation for further analyses.

Combined QTL mapping on bi-parental immortalized heterozygous populations to detect the genetic architecture on heterosis.

From bi-parental pure-inbred lines (PIL), immortalized backcross (i.e., IB1 and IB2, representing the two directions of backcrossing) and F2 (i.e., IF2) populations can be developed. These populations are suitable for genetic studies on heterosis, due to the present of both homozygous and heterozygous genotypes, and in the meantime allow repeated phenotyping trials across multiple locations and years. In this study, we developed a combined approach of quantitative trait locus (QTL) mapping, when some or all of the four immortalized populations (i.e., PIL, IB1, IB2, and IF2) are available. To estimate the additive and dominant effects simultaneously and accurately, suitable transformations are made on phenotypic values from different populations. When IB1 and IB2 are present, summation and subtraction are used. When IF2 and PIL are available, mid-parental values and mid-parental heterosis are used. One-dimensional genomic scanning is performed to detect the additive and dominant QTLs, based on the algorithm of inclusive composite interval mapping (ICIM). The proposed approach was applied to one IF2 population together with PIL in maize, and identified ten QTLs on ear length, showing varied degrees of dominance. Simulation studies indicated the proposed approach is similar to or better than individual population mapping by QTL detection power, false discovery rate (FDR), and estimated QTL position and effects.

Integrated morphological, physiological and omics analyses reveal the arylalkylamine N-acetyltransferase (AANAT) gene contributing to growth, flowering and defence in switchgrass (Panicum virgatum L.).

Arylalkylamine N-acetyltransferase (AANAT) catalyses the acetylation of serotonin, a rate-limiting process in melatonin biosynthesis. To obtain better insight into the underlying mechanism of AANAT's actions in switchgrass growth, flowering and defence, we performed integrated morphological, physiological and omics analyses between overexpressed oAANAT transgenic lines in wild-type and transgenic control (expressing only the empty vector) plants. We showed that oAANAT played pivotal roles in modulating plant growth through its regulation of cell elongation, and regulating flowering through photoperiod and GA pathways. In relation to photosynthesis, oAANAT promoted photosynthetic efficiency primarily through regulating leaf anatomical structures, stomatal development and chlorophyll metabolism. Moreover, oAANAT overexpression can trigger a number of defence responses or strategies, including antioxidant enzymatic properties, non-enzymatic capacity, significantly activated phenylpropanoid biosynthesis, and adaptive morphological characteristics. This study unveils the possible molecular mechanisms underlying oAANAT dependent melatonin functions in switchgrass, providing an important starting point for further analyses.