crassa, using a gene ( al-1) essential for biosynthesis of carotenoids, which provides a simple visual reporter for quelling. We have begun to use a molecular–genetic approach to dissect the mechanism of quelling in N. Moreover, these quelling mutants may be important in applied and basic research for the creation of strains able to overexpress a transgene.
The qde mutations may be used to isolate the genes encoding the first components of the quelling mechanism. As such, qde genes may be involved in sensing aberrant sense RNA and/or targeting/degrading the native mRNA. Moreover, the qde mutants failed to show quelling when tested with another gene, suggesting that they may be universally defective in transgene-induced gene silencing. We show that when qde genes are mutated in a transgenic-induced silenced strain containing many copies of the transgene, the expression of the endogenous gene is maintained despite the presence of transgene sense RNA, the molecule proposed to trigger quelling.
The recessive nature of the qde mutations indicates that the encoded gene products act in trans. These quelling-defective mutants ( qde) belonging to three complementation groups have provided insights into the mechanism of posttranscriptional gene silencing in N. We report the isolation of 15 Neurospora crassa mutants defective in “quelling” or transgene-induced gene silencing.
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