Comparative Transcriptome Analysis of Genes Involved in Sesquiterpene Alkaloid Biosynthesis in Trichoderma longibrachiatum MD33 and UN32

Trichoderma longibrachiatum MD33, a sesquiterpene alkaloid-producing endophyte isolated from Dendrobium nobile, shows potential medical and industrial applications. To understand the molecular mechanisms of sesquiterpene alkaloids production, a comparative transcriptome analysis was performed on strain MD33 and its positive mutant UN32, which was created using Ultraviolet (UV) mutagenesis and nitrogen ion (N+) implantation. The alkaloid production of UN32 was 2.62 times more than that of MD33. One thousand twenty-four differentially expressed genes (DEGs), including 519 up-regulated and 505 down-regulated genes, were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed 139 GO terms and 87 biosynthesis pathways. Dendrobine, arguably the main sesquiterpene alkaloid the strain MD33 produced, might start synthesis through the mevalonate (MVA) pathway. Several MVA pathway enzyme-coding genes (hydroxy-methylglutaryl-CoA synthase, mevalonate kinase, and farnesyl diphosphate synthase) were found to be differentially expressed, suggesting that physical mutagenesis can disrupt genome integrity and gene expression. Some backbone post-modification enzymes and transcript factors were either discovered, suggesting the sesquiterpene alkaloid metabolism in T. longibrachiatum is a complex genetic network. Our findings help to shed light on the underlying molecular regulatory mechanism of sesquiterpene alkaloids production in T. longibrachiatum.

Trichoderma longibrachiatum (TG1) Enhances Wheat Seedlings Tolerance to Salt Stress and Resistance to Fusarium pseudograminearum

Salinity is abiotic stress that inhibits seed germination and suppresses plant growth and root development in a dose-dependent manner. Fusarium pseudograminearum (Fg) is a plant pathogen that causes wheat crown rot. Chemical control methods against Fg are toxic to the environment and resistance has been observed in wheat crops. Therefore, an alternative approach is needed to manage this devastating disease and the effects of salinity. Our research focused on the mycoparasitic mechanisms of Trichoderma longibrachiatum (TG1) on Fg and the induction of defenses in wheat seedlings under salt and Fg stress at physiological, biochemical and molecular levels. The average inhibition rate of TG1 against Fg was 33.86%, 36.32%, 44.59%, and 46.62%, respectively, in the four NaCl treatments (0, 50, 100, and 150 mM). The mycoparasitic mechanisms of TG1 against Fg were coiling, penetration, and wrapping of Fg hyphae. In response to inoculation of TG1 with Fg, significant upregulation of cell wall degrading enzymes (CWDEs) was observed. The expression of β-1, 6-glucan synthase (PP4), endochitinase precursor (PH-1), and chitinase (chi18-15) increased by 1. 6, 1. 9, and 1.3-fold on day 14 compared with day 3. Wheat seedlings with combined TG1 + Fg treatments under different NaCl stress levels decreased disease index by an average of 51.89%; increased the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity by an average of 38%, 61%, and 24.96%, respectively; and decreased malondialdehyde (MDA) and hydrogen peroxide (H2O2) content by an average of 44.07% and 41.75% respectively, compared with Fg treated seedlings. The combined TG1 + Fg treatment induced the transcription level of plant defense-related genes resulting in an increase in tyrosin-protein kinase (PR2), chitinase class I (CHIA1), and pathogenesis-related protein (PR1-2) by an average of 1.15, 1.35, and 1.37-fold, respectively compared to Fg treatment. However, the expression levels of phenylalanine ammonia-lyase (PAL) increased 3.40-fold under various NaCl stresses. Our results suggest that TG1 enhances wheat seedling growth and controls wheat crown rot disease by strengthening the plant defense system and upregulating the expression of pathogenesis-related genes under both Fg and salt stress.

PRODUCTION OF ALPHA AMYLASE AND CELLULASE FROM SOLID STATE CULTURE OF ASPERGILLUS OCHRACEUS: A FEASIBILITY ANALYSIS

The growing demand and application of industrially important enzyme necessitate the need to explore new sources with diverse enzymes ranging in their specificity and activities. Enzymes are safe alternatives to chemical synthesis due to minimum side effect and ease of manufacturing. Solid state fermentation (SSF) is a cost-effective alternative to submerged fermentation with agro-residues or waste, often being used as substrate for growing diverse organisms for production of metabolites. Current study is one of the scarce report on exploring alpha amylase and cellulase production ability Aspergillus ochraceus (MTCC 1877) using wheat bran as substrate at relative humidity of 90% and at 30 ºC, for 7 days. Result showed the potential of Aspergillus ochraceus (MTCC 1877), as potential source of the two enzymes. Results revealed comparatively higher alpha amylase activity in the SSF extract of Aspergillus ochraceus (MTCC 1877) in comparison to Trichoderma longibrachiatum (ITCC 7839). On the contrary, comparatively higher cellulase activity was observed in the SSF extract of Trichoderma longibrachiatum (ITCC 7839). The results showed the potential of Aspergillus ochraceus (MTCC 1877) as a source of the two enzymes. Variation in enzymes activity may be attributed to the experimental culture conditions and may be further optimized to enhance the enzymes yield.

Meloidogyne enterolobii development and reproduction in tomato plants treated with resistance inducers

Summary Meloidogyne enterolobii is a species capable of overcoming plant resistance moderated by the Mi-1 gene, which is effective against most species of root-knot nematode. This study evaluated the effect of induced resistance in tomato plants (Solanum lycopersicum ‘H-9553’) with the Mi-1 gene against the development and reproduction of M. enterolobii. Seedlings of tomato ‘H-9553’ were transplanted into pots, inoculated with 2000 eggs and second-stage juveniles (J2) of M. enterolobii and treated with Acibenzolar-S-Methyl, Bacillus subtilis, B. subtilis + B. licheniformis + Trichoderma longibrachiatum and extract of Reynoutria sachalinensis. The plants were collected at 5, 10, 15, 20, 25 and 30 days after inoculation (DAI) for the analyses of nematode penetration and development, and at 30 DAI for nematode reproduction. The use of B. subtilis increased fresh root weight when compared to the other treatments (20 DAI). There was a reduction in penetration of J2 in the roots of plants subjected to different resistance inducers. The population density of M. enterolobii was significantly reduced only when plants were treated with R. sachalinensis, indicating it as a potential resistance-inducing agent in tomato plants.