Isolation of Arabidopsis mutants altered in the light‐regulation of chalcone synthase gene expression using a transgenic screening approach

Abstract

Transgenic Arabidopsis expressing beta-glucuronidase (GUS) driven by a chalcone synthase gene (CHS) promoter were produced. GUS activity in the leaves increased with increasing fluence rates of white light in parallel with endogenous CHS transcript levels. An isogenic line homozygous for the transgene was obtained and mutagenized seedlings of this line were screened for altered light-induction of the transgene. Putative mutants with low GUS activity were not altered in the light-induction of endogenous CHS transcripts and are therefore not regulatory mutants. Two mutant lines (A12 and C10) with elevated levels of GUS activity in the light show a corresponding increase in CHS transcript levels. The A12 mutant was focussed upon and designated icx1 (increased chalcone synthase expression). This mutant has enhanced light-stimulation of CHS expression since CHS transcript levels in darkness in icx1 are very low, as in the wild-type. The transcript levels of two other genes involved in flavonoid biosynthesis are elevated in the light in icx1 as is anthocyanin formation. However, there is no alteration in LHCII chlorophyll a/b-binding protein gene (CAB) transcript levels under the same conditions. The altered gene expression phenotype of icx1 co-segregates with several other phenotypic characteristics, including fewer leaf trichomes and alterations to the seed coat. On the basis of these data and comparison with the Arabidopsis ttg (transparent testa glabra) mutant, it is suggested that the ICX1 gene product may be concerned both with the light-regulation of gene expression and with developmental processes occurring in the epidermis.

Physiological factors affecting transcription of genes involved in the flavonoid biosynthetic pathway in different rice varieties

“…F3H, DFR, and ANS gene expression in sorghum mesocotyl dramatically decreased with light treatment, whereas that for CHS significantly increased 25 . It was observed that in Arabidopsis cell culture under low fluence white light resulted in very low CHS transcript levels induced in mature leaf tissue 43 , 44 . The flavonoid biosynthetic genes CHS and CHI showed high transcript abundance in high-light Mitchell plants, with weak signals observed for DFR and ANS.…”

An Arabidopsis Mutant Tolerant to Lethal Ultraviolet-B Levels Shows Constitutively Elevated Accumulation of Flavonoids and Other Phenolics

“…Thus, the UVB tolerance of uvt1 correlates with deregulated gene expression and may even be a consequence of it. Jackson et al (1995) described a mutant, icx1, which like uvt1 shows constitutively elevated CHS gene expression. The icx1 mutation differs from uvt1, however, in that it segregates as a single recessive lesion and that it leads to other phenotypic characteristics.…”

Genetic analysis of floral anthocyanin pigmentation traits in Asiatic hybrid lily using molecular linkage maps

“…Although many regulator proteins positively control the spatially regulated expression of sets of genes needed for the anthocyanin biosynthesis pathway (Mol et al 1998), the negative regulator intensifier1 was identified in maize (Burr et al 1996). Trait loci, of which the dominant allele suppressed the expression of sets of structural genes, were also characterized in Arabidopsis (icx1, Jackson et al 1995) and snapdragon (Eluta, Martin et al 1991), although their genes have not been cloned. The BANYULS gene that encodes a DFR-like structural protein (LCR) reduces the anthocyanin accumulation in Arabidopsis seed coats (Devic et al 1999).…”