Update on transparent testa mutants from Arabidopsis thaliana: characterisation of new alleles from an isogenic collection

Abstract

We present a comprehensive overview on flavonoid-related phenotypes of A. thaliana tt and tds mutants, provide tools for their characterisation, increase the number of available alleles and demonstrate that tds3 is allelic to tt12 and tds5 to aha10. Flavonoid biosynthesis is one of the best-studied secondary metabolite pathways in plants. In the model system Arabidopsis thaliana it leads to the synthesis of three phenolic compound classes: flavonol glycosides, anthocyanins and proanthocyanidins (PAs). PAs appear brown in their oxidised polymeric forms, and most A. thaliana mutants impaired in flavonoid accumulation were identified through screens for lack of this seed coat pigmentation. These mutants are referred to as transparent testa (tt) or tannin-deficient seed (tds). More than 20 mutants of these types have been published, probably representing most of the genes relevant for PA accumulation in A. thaliana. However, data about the genes involved in PA deposition or oxidation are still rather scarce. Also, for some of the known mutants it is unclear if they represent additional loci or if they are allelic to known genes. For the present study, we have performed a systematic phenotypic characterisation of almost all available tt and tds mutants and built a collection of mutants in the genetic background of the accession Columbia to minimise effects arising from ecotype variation. We have identified a novel tt6 allele from a forward genetic screen and demonstrated that tds3 is allelic to tt12 and tds5 to aha10.

The MYB107 Transcription Factor Positively Regulates Suberin Biosynthesis

“…Its seeds also have no tt phenotype (Supplemental Fig. S4C), as seen in other tt mutants (Debeaujon et al, 2000;Appelhagen et al, 2014). These data suggest that MYB107 controls seed coat permeability by specifically regulating suberin biosynthesis but not other elements contributing to the seed-sealing property.…”

“…KCS2 and KCS20 are the fatty acid elongases functionally redundant in the two-carbon elongation to very-long-chain fatty acids that is required for the biosynthesis of cuticular waxes and root suberin ( The recently identified suberin ATP-binding cassette transporter genes ABCG2, ABCG6, and ABCG20 (Yadav et al, 2014) did not experience significant downregulation in myb107 ( Table I), suggesting that MYB107 does not affect the expression of genes involved in the process of polyester monomer transport/ deposition. In addition, genes involved in seed coat pigmentation, namely the TRANSPARENT TESTA (TT) genes (Debeaujon et al, 2000;Appelhagen et al, 2014), also did not show significant changes (Supplemental Table S3; Supplemental Data Set S1).…”

The AtMYB12 activation domain maps to a short C-terminal region of the transcription factor

“…All three alleles have been shown to encode nonfunctional versions of the genes. The flavonoid-deficient transparent testa4 (tt4-11, SALK_020583) mutant, carrying a loss-of-function chalcone synthase (chs) allele [11], is compromised in the first enzymatic step of flavonoid biosynthesis [12]. The seeds used in the present study are from the same batch.…”

Gene expression analysis of bud and leaf color in tea

“…In model plant Arabidopsis, a number of genes involved in anthocyanin biosynthesis, transportation and regulation were characterized to be involved in anthocyanin accumulation (Appelhagen et al, 2014). Among them, a TTG1/bHLH/Myb transcriptional complex plays a key role in regulating anthocyanin biosynthetic pathway (Gonzales et al, 2008).…”