Exploring the Distribution of Citrinin Biosynthesis Related Genes among Monascus Species

Abstract

Citrinin, a hepato-nephrotoxic compound to humans, can be produced by the food fermentation microorganisms Monascus spp. In this study, we investigated the distribution of mycotoxin citrinin biosynthesis genes in 18 Monascus strains. The results show that the acyl-transferase and keto-synthase domains of the pksCT gene encoding citrinin polyketide synthase were found in Monascus purpureus, Monascus kaoliang, and Monascus sanguineus. Furthermore, the ctnA gene, a major activator for citrinin biosynthesis, was found in M. purpureus and M. kaoliang, but was absent in M. sanguineus. The orf3 gene encoding oxygenase, located between pksCT and ctnA, was also present in M. purpureus and M. kaoliang. The pksCT gene was highly conserved in M. purpureus, M. kaoliang, and M. sanguineus, while the ctnA and orf3 genes were shown to be highly homologous in M. purpureus and M. kaoliang. In contrast, the PCR and Southern blot analyses suggest that pksCT, ctnA, and orf3 were absent or significantly different in Monascus pilosus, Monascus ruber, Monascus barkeri, Monascus floridanus, Monascus lunisporas, and Monascus pallens. A citrinin-producing phenotype was detected only in M. purpureus and M. kaoliang using high performance liquid chromatography (HPLC). These results clearly indicate that the highly conserved citrinin gene cluster in M. purpureus and M. kaoliang carry out citrinin biosynthesis. In addition, according to the phylogenetic subgroups established with the beta-tubulin gene, the citrinin gene cluster can group the species of Monascus.

Identification of citrinin biosynthesis gene under the ultrasonic induction of Monascus purpureus

“…Our partial citrinin biosynthesis gene results in agreement with the report of Chen et al, 2008 [18] who investigated the distribution of mycotoxin citrinin biosynthesis genes in 18 Monascus strains. The results show that the acyl-transferase and ketosynthase domains of the pksCT gene encoding citrinin polyketide synthase were found in Monascus purpureus, Monascus kaoliang, and Monascus sanguineus.…”

“…A polyketide synthase gene (pksCT) containing eight typical domins [ketosynthase (KS), acyl transferase (AT), ketoreductase (KR), dehydratase (DH), enoyl reductase (ER), methyltransferase (MT), thioesterase (TE), and acyl carrier protein (ACP)] was correlated with microtoxin production in fungi [7,13,14]. Especially, between the 5' region the KS domain and the 3' region the ACP domain that indicate the AT region of pksCT gene is responsible for citrinin biosynthesis because the strain of M. purpureus which was disrupted in this area did not produce citrinin [7,[17][18][19]. This area of the pksCT gene in M. purpuereus TISTR 3541 wild type in our investigation after the treating with the ultrasonic wave to generate the mutants was determined in study.…”

Lower Citrinin Production by Gene Disruption of ctnB Involved in Citrinin Biosynthesis in Monascus aurantiacus Li AS3.4384

“…8 The distribution of mycotoxin citrinin biosynthesis genes in 18 Monascus strains has also been previously investigated. 9 The production of citrinin in Monascus is consistent with the presence of the functional citrinin biosynthesis genes found only in M. purpureus and Monascus kaoliang. The strains of Monascus ruber, Monascus pilosus, and Monascus barkeri have been found to neither possess the pksCT, ctnA, and orf 3 genes nor able to produce citrinin.…”

Isolation and characterization of the citrinin biosynthetic gene cluster from Monascus aurantiacus

“…Our results are in agreement with the findings of Chen et al (2008) that the pksCT was highly conserved, while the ctnA and orf3 were homologous. The citrinin gene cluster consisting of the six genes and additional copies of ctnA were introduced into A. oryzae via transformation.…”