Virus-induced gene silencing (VIGS) is a technology for rapid gene functional analysis that depends on the degradation of viral RNA and is part of the natural defense mechanism in plants. Senecio cruentus is an important Compositae ornamental species that is plentiful and available in a variety of colors and has a typical blue variety that is rare in Compositae. These advantages make it a good material for studying the anthocyanin biosynthesis and blue flower formation mechanism. With the development of gene sequencing technology, the functions of many candidate genes that may be involved in anthocyanin biosynthesis in S. cruentus need to be identified. However, a stable and rapid genetic transformation system of S. cruentus is still lacking. Here, we screened two cultivars, 'Venezia' and 'Jseter', selected ScPDS and ScANS as test genes, and investigated the effect of developmental periods, bacterial cell concentrations and infection methods on gene silencing efficiency. The results showed that the silencing efficiency of S. cruentus leaves was low (13%), and it was less affected by the parameters. However, the transcription factor gene ScbHLH17 was still silenced by VIGS, which resulted in the loss of anthocyanin accumulation in leaves, and the expression levels of anthocyanin biosynthesis pathway (ABP) structural genes, including ScCHI, ScDFR3 and ScANS, were decreased significantly. The result proved that ScbHLH17 was an important transcription factor that regulated flower color formation in S. cruentus. In addition, ScANS-silencing phenotypes were observed in S. cruentus capitulum by vacuum-infiltrating S1 stage buds for 10 min after scape injection. In general, the present study provided an important technical support for the study of anthocyanin metabolism pathways in S. cruentus.
Keywords: Anthocyanin; Senecio cruentus; VIGS; bHLH17.
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