The Dominant Inhibitory Chalcone Synthase Allele C2-Idf (Inhibitor diffuse) From Zea mays (L.) Acts via an Endogenous RNA Silencing MechanismSequence data from this article have been deposited with the EMBL/GenBank Data Libraries under accession nos. AY728478 [c2 gene chalcone synthase (wild type) C2-W22], AY728476 (Zea mays L. C2-Idf allele; gene copies C2-Idf-I and C2-Idf-II), and AY728477 (Zea mays L. C2-Idf allele; gene copy <

Abstract

The flavonoid pigment pathway in plants has been used as a model system for studying gene regulatory mechanisms. C2-Idf is a stable dominant mutation of the chalcone synthase gene, c2, which encodes the first dedicated enzyme in this biosynthetic pathway of maize. Homozygous C2-Idf plants show no pigmentation. This allele also inhibits expression of functional C2 alleles in heterozygotes, producing a less pigmented condition instead of the normal deeply pigmented phenotype. To explore the nature of this effect, the C2-Idf allele was cloned. The gene structure of the C2-Idf haplotype differs substantially from that of the normal c2 gene in that three copies are present. Two of these are located in close proximity to each other in a head-to-head orientation and the third is closely linked. Previous experiments showed that the lower level of pigmentation in heterozygotes is correlated with reduced enzyme activity and low steady-state mRNA levels. We found that c2 transcription occurs in nuclei of C2-Idf/C2 heterozygotes, but mRNA does not accumulate, suggesting that the inhibition is mediated by RNA silencing. Infection of C2-Idf/C2 heterozygotes with viruses that carry suppressors of RNA silencing relieved the phenotypic inhibition, restoring pigment production and mRNA levels. Finally, we detected small interfering RNAs (siRNAs) in plants carrying C2-Idf, but not in plants homozygous for the wild-type C2 allele. Together, our results indicate that the inhibitory effect of C2-Idf occurs through RNA silencing.

Functional analysis of soybean genes involved in flavonoid biosynthesis by virus‐induced gene silencing

“…The very low mRNA levels of CHS genes in seed coats after the CHS VIGS treatment (Figure 3) indicate that at least the CHS7 / CHS8 genes are markedly down‐regulated, just like in the yellow seed coats, in which CHS silencing is naturally induced. To date, there have been four reports of natural post‐transcriptional gene silencing (PTGS) phenomena (Kusaba et al ., 2003; Della Vedova et al ., 2005; Koseki et al ., 2005), including the yellow seed coats in soybean (Senda et al ., 2004). Thus, we have directly demonstrated the natural PTGS in the soybean by reproducing the phenomenon using VIGS of CHS .…”

Deep sequencing uncovers commonality in small RNA profiles between transgene-induced and naturally occurring RNA silencing of chalcone synthase-A gene in petunia

“…The generation of the star-type petunia flowers as a consequence of hybridization between plant lines suggests that the RNA silencing ability can be conferred via the shuffling of genomes that differ slightly from each other [20]. Similar naturally occurring RNA silencing has been reported for a picotee-type variety of petunia, which has nonpigmented sectors in the outer edge of the petal tissues [24], and for other plants such as rice [25], soybean [26-29], maize [30] and dahlia [31]. …”

Genome-Wide Identification, Characterization and Expression Analysis of the Chalcone Synthase Family in Maize

“…A number of aspects on regulation and function of CHS family have been investigated in many plants, including grape [ 15 ], Gerbera hybrida [ 16 ], apple [ 17 ], Oncidium orchid [ 18 ], Hypericum sampsonii [ 10 ], Arabidopsis [ 19 ], Petunia [ 20 ] and bean [ 21 ]. Two maize CHS genes were previously reported, C2 and Whp [ 22 , 23 ]. Moreover, one anther specific chalcone synthase-like ( ASCL ) gene ( ZmCHSL , NP_001149508) was also reported by Jepson et al [ 24 ].…”