The Tomato Hoffman’s Anthocyaninless Gene Encodes a bHLH Transcription Factor Involved in Anthocyanin Biosynthesis That Is Developmentally Regulated and Induced by Low Temperatures

Abstract

Anthocyanin pigments play many roles in plants, including providing protection against biotic and abiotic stresses. Many of the genes that mediate anthocyanin accumulation have been identified through studies of flowers and fruits; however, the mechanisms of genes involved in anthocyanin regulation in seedlings under low-temperature stimulus are less well understood. Genetic characterization of a tomato inbred line, FMTT271, which showed no anthocyanin pigmentation, revealed a mutation in a bHLH transcription factor (TF) gene, which corresponds to the ah (Hoffman's anthocyaninless) locus, and so the gene in FMTT271 at that locus was named ah. Overexpression of the wild type allele of AH in FMTT271 resulted in greater anthocyanin accumulation and increased expression of several genes in the anthocyanin biosynthetic pathway. The expression of AH and anthocyanin accumulation in seedlings was shown to be developmentally regulated and induced by low-temperature stress. Additionally, transcriptome analyses of hypocotyls and leaves from the near-isogenic lines seedlings revealed that AH not only influences the expression of anthocyanin biosynthetic genes, but also genes associated with responses to abiotic stress. Furthermore, the ah mutation was shown to cause accumulation of reactive oxidative species and the constitutive activation of defense responses under cold conditions. These results suggest that AH regulates anthocyanin biosynthesis, thereby playing a protective role, and that this function is particularly important in young seedlings that are particularly vulnerable to abiotic stresses.

Early metabolic and transcriptional variations in fruit of natural white-fruited Fragaria vesca genotypes

“…Among the significantly down-regulated candidates is also gene31672, a glutathione S-transferase (GST, Table 1) orthologous to GST Solyc02g081340 from tomato ( Solanum lycopersicum ). Transgenic tomato fruits exhibiting higher anthocyanin content showed increased expression of Solyc02g0813404041, whereas expression in the anthocyanin absent mutant was barely detectable42. It has been proposed that anthocyanins might be transported into vacuoles via the noncovalent activity of GSTs43.…”

Allelic Variation and Transcriptional Isoforms of Wheat TaMYC1 Gene Regulating Anthocyanin Synthesis in Pericarp

“…In rice, a mutation in the bHLH domain of the RC protein is responsible for the white pericarp phenotype of the grain (Sweeney et al, 2006 ). Homologs of the maize R and B TFs controlling anthocyanin biosynthesis in specific tissues are also known in Antirrhinum ( Delila ) (Carpenter et al, 1991 ), petunia ( Jaf13 ) (Quattrocchio et al, 1998 ), tomato ( AH ) (Qiu et al, 2016 ), and Ipomoea purpurea ( bHLH2 ) (Park et al, 2007 ).…”

A high-density genetic map developed by specific-locus amplified fragment (SLAF) sequencing and identification of a locus controlling anthocyanin pigmentation in stalk of Zicaitai (Brassica rapa L. ssp. chinensis var. purpurea)

“…However, the molecular mechanism for MBW components regulating anthocyanin biosynthesis in response to environmental stimuli is largely unknown [56]. In tomato, a bHLH TF AH was identified to be involved in anthocyanin biosynthesis that is developmentally regulated and induced by low temperature [57]. In apple, the molecular mechanism by which MdbHLH3 regulates low temperature induced anthocyanin accumulation was identified [58].…”