RNA-Seq based exploration of differentially expressed genes (DEGs) in cotton(Gossypium hirsutum. L) upon infection with Aspergillus tubingensis

Differentially expressed genes help in exploring plant defense mechanism under variable stress conditions. In current investigation, RNA sequencing was executed to explore the differential gene expression in resistant and susceptible varieties of Cotton (Gossypium hirsutum), upon infection with Aspergillus tubingensis. Comparative RNA-Seq of control and infected plants was performed using Illumina HiSeq 2,500. Overall 79.84 G clean data was generated and 6,558 DEGs were identified in both varieties, in response to pathogen inoculation. Differentially expressed genes were found to be involved in defense, antifungal response, signaling pathways, oxidative burst and transcription. Genes involved in defense responses, MAPK signaling, cell wall fortification and signal transduction were highly induced in resistant variety. Real time PCR also revealed the up regulation of MAPKKK YODA like, L-ascorbate oxidase, late embryogenesis abundant protein (At1g64065) and flavonoid 3',5'-hydroxylase-like, in resistant variety. Elevated accumulation of such DEGs in resistant variety could function as the source for identifying biomarkers for breeding and these can be used as potential candidate genes for transgenic manipulation. Their study also helped in understanding complex plant-fungal interaction and advanced the understanding of plant-microbe interaction. Inclusively, our findings provide an indispensable foundation for advanced understanding of the plant resistance mechanisms of cotton.

Optimization of Conditions for Xylanase Production Using Aspergillus tubingensis Under Different Carbon Sources

Xylanases are hydrolytic enzymes with wide range of applications in food processing, bleaching of pulp in paper manufacturing industry, bio-conversion of biomass wastes to fermentable sugars and enhancing nutrient digestibility in animal feeds. The optimization of growth conditions and evaluation of an appropriate substrate as carbon source among cassava peels, corn cobs, wheat bran and rice husk on xylanase production by novel strain of Aspergillus tubingensis under Solid State Fermentation (SSF) was investigated. The fungal isolate was identified based on ribosomal RNA gene and ITS gene sequencing analysis as Aspergillus tubingensis. Results showed that Corn cobs had the highest xylanase production among the four substrates. Corn cobs recorded the highest value of xylanase production at pH of 6.0 (107.97 U/g), after incubation period of 72 hour (111.23 U/g), at temperature of 30oC (44.26 U/g) and at ratio 1:3 (45.68 U/g). The optimum growth conditions for xylanase production by Aspergillus tubingensis were: pH 6.0, incubation period of 72 hours, temperature of 30oC and substrate concentration of 1:3 (4g of substrate per 12ml of fermentation medium). Corn cobs showed the highest yield of xylanase activity (111.23±0.31 U/g), followed by Rice husk (101.91±0.72 U/g), Wheat bran (89.30±1.16 U/g) and Cassava peel (87.03±0.57 U/g). In conclusion, among the various agro residues that were used as carbon sources, Corn cobs had maximum xylanase activity. Various culture conditions were optimized by using one factor at a time method and the maximum xylanase production was obtained at pH of 6.0, incubation period of 72 hour, temperature of 30oC and substrate concentration of 1:3 under solid state fermentation. It is therefore suggested that some other notable environmental and fermentation factors that influence metabolism-mediated production yields of xylanase like aeration, agitation, carbon and nitrogen sources, metal ion requirement, inoculum size etc. should be optimized for maximum production of enzyme. Keywords: Solid State Fermentation, Cassava peels, Corn cobs, Wheat bran, Rice husk

Genome Sequencing and Analysis Reveal the Mechanism of Terpenoids Biosynthesis in Deep-See-Derived Fungus Aspergillus Tubingensis

In recent years, deep-sea-derived fungi have become an important source of marine natural products. Aspergillus tubingensis is extremely rich in secondary metabolites, which is a valuable deep-sea-derived fungus needs to be further explored. So far, many small molecular compounds with novel structure and significant biological activity have been discovered from A. tubingensis, among which terpenoids account for about 20%, showing great research potential in anti-tumor, antiviral and antibacteria. Although more and more new terpenoids have been discovered from A. tubingensis and their structures have been identified, few studies have investigated the biosynthetic pathway of terpenoid. In order to further elucidate the mechanism of terpenoid biosynthesis, the key genes and enzymes involved in terpenoid biosynthesis were successfully mined and further analyzed based on genome sequencing analysis. Subsequently, hydroxymethylglutaryl-CoA synthase, mevalonate kinase, phosphomevalonate kinase as well as diphosphomevalonate decarboxylase were annotated, which played important roles in terpenoid biosynthesis of A. tubingensis. Furthermore, the biosynthetic pathway of terpenoid in A. tubingensis has been constructed, which could be applied to develop the metabolic regulation of A. tubingensis. This study would provide more sufficient scientific basis and new ideas for the genetic regulation of terpenoid biosynthesis in A. tubingensis.