Genome-wide Identification and Characterization of Natural Antisense Transcripts by Strand-specific RNA Sequencing in Ganoderma lucidum

Genome-wide view and characterization of natural antisense transcripts in Cannabis Sativa L

Natural Antisense Transcripts (NATs) are a kind of complex regulatory RNAs that play crucial roles in gene expression and regulation. However, the NATs in Cannabis Sativa L., a widely economic and medicinal plant rich in cannabinoids remain unknown. In this study, we comprehensively predicted C. sativa NATs genome-wide using strand-specific RNA sequencing (ssRNA-Seq) data, and validated the expression profiles by strand-specific quantitative reverse transcription PCR (ssRT-qPCR). Consequently, a total of 307 NATs were predicted in C. sativa, including 104 cis- and 203 trans- NATs. Functional enrichment analysis demonstrated the potential involvement of the C. sativa NATs in DNA polymerase activity, RNA-DNA hybrid ribonuclease activity, and nucleic acid binding. Finally, 18 cis- and 376 trans- NAT-ST pairs were predicted to produce 621 cis- and 5,679 trans- small interfering RNA (nat-siRNAs), respectively. These nat-siRNAs were potentially involved in the biosynthesis of cannabinoids and cellulose. All these results will shed light on the regulation of NATs and nat-siRNAs in C. sativa.

Unraveling the Polysaccharide Biosynthesis Potential of Ganoderma lucidum: A Chromosome-Level Assembly Using Hi-C Sequencing

Ganoderma lucidum exhibits the ability to synthesize a diverse range of biologically active molecules with significant pharmaceutical potential, including xylomannan and fucogalactan, which have demonstrated antitumor activity. However, there exists considerable intra-species variability in the capacity to produce these metabolites at high concentrations, likely reflecting the high genomic diversity observed from a limited number of strains sequenced to date. We employed high-throughput shotgun sequencing to obtain the complete genome sequence of G. lucidum strain 5.1, which is distinguished by its remarkable xylomannan synthesis capabilities. Through the utilization of semi-automatic reordering based on conformation capture (Hi-C) data, we substantially enhanced the assembly process, resulting in the generation of 12 chromosome-level scaffolds with a cumulative length of 39 Mbp. By employing both de novo and homology-based approaches, we performed comprehensive annotation of the genome, thereby identifying a diverse repertoire of genes likely involved in polysaccharide biosynthesis. The genome sequence generated in this study serves as a valuable resource for elucidating the molecular mechanisms underlying the medicinal potential of Ganoderma species, discovering novel pharmaceutically valuable compounds, and elucidating the ecological mechanisms of the species. Furthermore, the chromosome contact map obtained for the first time for this species extends our understanding of 3D fungal genomics and provides insights into the functional and structural organization within the fungal kingdom.

Gene age shapes the transcriptional landscape of sexual morphogenesis in mushroom forming fungi (Agaricomycetes)

Multicellularity has been one of the most important innovations in the history of life. The role of gene regulatory changes in driving transitions to multicellularity is being increasingly recognized; however, factors influencing gene expression patterns are poorly known in many clades. Here, we compared the developmental transcriptomes of complex multicellular fruiting bodies of eight Agaricomycetes and Cryptococcus neoformans, a closely related human pathogen with a simple morphology. In-depth analysis in Pleurotus ostreatus revealed that allele-specific expression, natural antisense transcripts, and developmental gene expression, but not RNA editing or a ‘developmental hourglass,’ act in concert to shape its transcriptome during fruiting body development. We found that transcriptional patterns of genes strongly depend on their evolutionary ages. Young genes showed more developmental and allele-specific expression variation, possibly because of weaker evolutionary constraint, suggestive of nonadaptive expression variance in fruiting bodies. These results prompted us to define a set of conserved genes specifically regulated only during complex morphogenesis by excluding young genes and accounting for deeply conserved ones shared with species showing simple sexual development. Analysis of the resulting gene set revealed evolutionary and functional associations with complex multicellularity, which allowed us to speculate they are involved in complex multicellular morphogenesis of mushroom fruiting bodies.

SnoRD126 promotes the proliferation of hepatocellular carcinoma cells through transcriptional regulation of FGFR2 activation in combination with hnRNPK

Liver cancer is the sixth most common malignancy and the fourth leading cause of cancer-related death worldwide. Hepatocellular carcinoma (HCC) is the primary type of liver cancer. Small nucleolar RNA (snoRNA) dysfunctions have been associated with cancer development. SnoRD126 is an orphan C/D box snoRNA. How snoRD126 activates the PI3K-AKT pathway, and which domain of snoRD126 exerts its oncogenic function was heretofore completely unknown. Here, we demonstrate that snoRD126 binds to hnRNPK protein to regulate FGFR2 expression and activate the PI3K-AKT pathway. Importantly, we identified the critical domain of snoRD126 responsible for its cancer-promoting functions. Our study further confirms the role of snoRD126 in the progression of HCC and suggests that knockdown snoRD126 may be of potential value as a novel therapeutic approach for the treatment of HCC.

Genome-wide identification and functional characterization of natural antisense transcripts in Salvia miltiorrhiza

Salvia miltiorrhiza is one of the most widely used traditional medicines. Natural antisense transcripts (NATs) are a class of long noncoding RNAs that can regulate gene expression. Here, we identified 812 NATs, including 168 cis-NATs and 644 trans-NATs from twelve root, flower, and leaf samples of S. miltiorrhiza using RNA-seq. The expression profiles for 41 of 50 NATs and their sense transcripts (STs) obtained from RNA-Seq were validated using qRT-PCR. The expression profiles of 17 NATs positively correlated with their STs. GO and KEGG pathway analyses mapped the STs for cis-NATs to pathways for biosynthesis of secondary metabolites. We characterized four NATs in detail, including NAT0001, NAT0002, NAT0004, and NAT00023. Their STs are kaurene synthase-like 1 and the homologs of UDP-glucose flavonoid 3-O-glucosyltransferase 6, UDP-glycosyltransferase 90A1, and beta-glucosidase 40, respectively. The first gene is involved in the biosynthesis of bioactive tanshinones, the next two are involved in anthocyanin biosynthesis, whereas the last is involved in phenylpropanoid biosynthesis. Besides, we found seven STs that are potential targets of miRNAs. And we found two miRNAs including miR156a and miR7208, might originate from NATs, NAT0112 and NAT0086. The results suggest that S. miltiorrhiza NATs might interact with STs, produce miRNAs, and be regulated by miRNAs. They potentially play significant regulatory roles in the biosynthesis of bioactive compounds.

Transcriptome Analysis Reveals the Molecular Mechanisms Underlying Adenosine Biosynthesis in Anamorph Strain of Caterpillar Fungus

Caterpillar fungus is a well-known fungal Chinese medicine. To reveal molecular changes during early and late stages of adenosine biosynthesis, transcriptome analysis was performed with the anamorph strain of caterpillar fungus. A total of 2,764 differentially expressed genes (DEGs) were identified (p ≤ 0.05, |log₂ Ratio| ≥ 1), of which 1,737 were up-regulated and 1,027 were down-regulated. Gene expression profiling on 4–10 d revealed a distinct shift in expression of the purine metabolism pathway. Differential expression of 17 selected DEGs which involved in purine metabolism (map00230) were validated by qPCR, and the expression trends were consistent with the RNA-Seq results. Subsequently, the predicted adenosine biosynthesis pathway combined with qPCR and gene expression data of RNA-Seq indicated that the increased adenosine accumulation is a result of down-regulation of ndk, ADK, and APRT genes combined with up-regulation of AK gene. This study will be valuable for understanding the molecular mechanisms of the adenosine biosynthesis in caterpillar fungus.

Identification and characterization of circular RNAs in Ganoderma lucidum

Circular RNAs (circRNAs) play important roles in animals, plants, and fungi. However, no circRNAs have been reported in Ganoderma lucidum. Here, we carried out a genome-wide identification of the circRNAs in G.lucidum using RNA-Seq data, and analyzed their features. In total, 250 and 2193 circRNAs were identified from strand-specific RNA-seq data generated from the polyA(−) and polyA(−)/RNase R-treated libraries, respectively. Six of 131 (4.58%) predicted circRNAs were experimentally confirmed. Across three developmental stages, 731 exonic circRNAs (back spliced read counts ≥ 5) and their parent genes were further analyzed. CircRNAs were preferred originating from exons with flanking introns, and the lengths of the flanking intron were longer than those of the control introns. A total of 200 circRNAs were differentially expressed across the three developmental stages of G. lucidum. The expression profiles of 119 (16.3%) exonic circRNAs and their parent genes showed significant positive correlations (r ≥ 0.9, q < 0.01), whereas 226 (30.9%) exonic circRNAs and their parent genes exhibited significant negative correlations (r ≤ −0.9, q < 0.01), in which 53 parent genes are potentially involved in the transcriptional regulation, polysaccharide biosynthesis etc. Our results indicated that circRNAs are present in G. lucidum, with potentially important regulatory roles.

Transcriptome analysis of three cultivars of Poria cocos reveals genes related to the biosynthesis of polysaccharides

Poria cocos (P. cocos) polysaccharides (PCPs) are used to improve immunity and possess antitumor activities. We compared three cultivars of P. cocos (5.78, XJ 28 and JHYH) PCP contents. Then we determined that malZ, galA, SORD, gnl and bglX are key enzymes within the PCP biosynthetic pathway by using HiSeq2500 transcriptome and qRT-PCR validation. Our results provide more detailed information about the PCP biosynthesis pathway at the molecular level in P. cocos and establish the functions for the molecular breeding to produce polysaccharides in general for therapeutic use in Chinese medicinal plants.

Improved nucleic acid extraction protocols for Ganoderma boninense, G. miniatocinctum and G. tornatum

The first and most crucial step of all molecular techniques is to isolate high quality and intact nucleic acids. However, DNA and RNA isolation from fungal samples are usually difficult due to the cell walls that are relatively unsusceptible to lysis and often resistant to traditional extraction procedures. Although there are many extraction protocols for Ganoderma species, different extraction protocols have been applied to different species to obtain high yields of good quality nucleic acids, especially for genome and transcriptome sequencing. Ganoderma species, mainly G. boninense causes the basal stem rot disease, a devastating disease that plagues the oil palm industry. Here, we describe modified DNA extraction protocols for G. boninense, G. miniatocinctum and G. tornatum, and an RNA extraction protocol for G. boninense. The modified salting out DNA extraction protocol is suitable for G. boninense and G. miniatocinctum while the modified high salt and low pH protocol is suitable for G. tornatum. The modified DNA and RNA extraction protocols were able to produce high quality genomic DNA and total RNA of ~ 140 to 160 µg/g and ~ 80 µg/g of mycelia respectively, for Single Molecule Real Time (PacBio Sequel^® System) and Illumina sequencing. These protocols will benefit those studying the oil palm pathogens at nucleotide level.