The nonribosomal peptide and polyketide synthetic gene clusters in two strains of entomopathogenic fungi inCordyceps

Genomic Comparative Analysis of Cordyceps pseudotenuipes with Other Species from Cordyceps

The whole genome of Cordyceps pseudotenuipes was sequenced, annotated, and compared with three related species to characterize the genome. The antibiotics and Secondary Metabolites Analysis Shell (antiSMASH) and local BLAST analysis were used to explore the secondary metabolites (SMs) and biosynthesis gene clusters (BGCs) of the genus Cordyceps. The genome-wide basic characteristics of C. pseudotenuipes, C. tenuipes, C. cicadae, and C. militaris revealed unequal genome size, with C. cicadae as the largest (34.11 Mb), followed by C. militaris (32.27 Mb). However, the total gene lengths of C. pseudotenuipes and C. tenuipes were similar (30.1 Mb and 30.06 Mb). The GC contents of C. pseudotenuipes, C. tenuipes, C. cicadae, and C. militaris genomes differed slightly (51.40% to 54.11%). AntiSMASH and local BLAST analysis showed that C. pseudotenuipes, C. tenuipes, C. cicadae, and C. militaris had 31, 28, 31, and 29 putative SM BGCs, respectively. The SM BGCs contained different quantities of polyketide synthetase (PKS), nonribosomal peptide synthetase (NRPS), terpene, hybrid PKS + NRPS, and hybrid NRPS + Other. Moreover, C. pseudotenuipes, C. tenuipes, C. cicadae, and C. militaris had BGCs for the synthesis of dimethylcoprogen. C. pseudotenuipes, C. tenuipes, and C. cicadae had BGCs for the synthesis of leucinostatin A/B, neosartorin, dimethylcoprogen, wortmanamide A/B, and beauvericin. In addition, the SM BGCs unique to C. pseudotenuipes were clavaric acid, communesin, and deoxynivalenol. Synteny analysis indicated that the scaffolds where the SM BGC was located were divided into more than 70 collinear blocks, and there might be rearrangements. Altogether, these findings improved our understanding of the molecular biology of the genus Cordyceps and will facilitate the discovery of new biologically active SMs from the genus Cordyceps using heterologous expression and gene knockdown methods.

Reliable reference gene selection for Cordyceps militaris gene expression studies under different developmental stages and media

Cordyceps militaris is considered a model organism for the study of Cordyceps species, which are highly prized in traditional Chinese medicine. Gene expression analysis has become more popular and important in studies of this fungus. Reference gene validation under different experimental conditions is crucial for RT-qPCR analysis. In this study, eight candidate reference genes, actin, cox5, gpd, rpb1, tef1, try, tub, and ubi, were selected and their expression stability was evaluated in C. militaris samples using four algorithms, genorm, normfinder, bestkeeper, and the comparative ∆Ct method. Three sets of samples, five different developmental stages cultured in wheat medium and pupae, and all the samples pool were included. The results showed that rpb1 was the best reference gene during all developmental stages examined, while the most common reference genes, actin and tub, were not suitable internal controls. Cox5 also performed poorly and was less stable in our analysis. The ranks of ubi and gpd were inconsistent in different sample sets by different methods. Our results provide guidelines for reference gene selection at different developmental stages and also represent a foundation for more accurate and widespread use of RT-qPCR in C. militaris gene expression analysis.