Induction of Anthocyanin Accumulation by Cytokinins in Arabidopsis thaliana

Abstract

Arabidopsis thaliana plants treated with exogenous cytokinins accumulate anthocyanin pigments. We have characterized this response because it is potentially useful as a genetic marker for cytokinin responsiveness. Levels of mRNAs for four genes of the anthocyanin biosynthesis pathway, phenylalanine ammonia lyase 1 (PAL1 ), chalcone synthase (CHS), chalcone isomerase (CHI), and dihydroflavonol reductase (DFR) were shown to increase coordinately in response to benzyladenine (BA). However, nuclear run-on transcription experiments suggested that although CHS and DFR are controlled by BA at the transcriptional level, PALl and CHI are controlled by BA posttranscriptionally. CHS mRNA levels increased within 2 h of BA spray application, and peaked by 3 h. Levels of PALl mRNA did not increase within 6 h of BA spray. We also showed that PAL1, CHS, CHI, and DFR mRNA levels fluctuate during a 24-h period and appear to be controlled by a circadian clock. The relation between cytokinin regulation and light regulation of CHS gene transcription is discussed.Cytokinins are important regulators of many aspects of plant development, including cell division, nutrient mobilization, senescence, chloroplast development, and apical dominance (Binns, 1994). Despite the widely acknowledged importance of cytokinin in plant development, very little is known about its mechanism of action at the molecular level.Cytokinins have been shown to affect the expression of specific genes by both increasing and decreasing the abundance of particular proteins or "As.A partia1 list of genes that are up-regulated by cytokinin includes nitrate reductase, rbcS, cab, hydroxypyruvate reductase in excised pumpkin cotyledons, a "multiple stimulus response" gene in Nicotiana plumbaginifolia cells, the early nodulin gene SrEnod2 from Sesbania rostrata, and a number of unidentified cDNAs from cultured soybean cells (Flores and Tobin, 1986;Chen, 1989;Crowell et al., 1990;Stabel et al., 1990;Dehio and de Bruijn, 1992;Dominov et al., 1992). Expression of phytochrome and a cucumber gene encoding a cDNA called CR9 are repressed by cytokinin (Cotton et al., 1990;Teramoto et al., 1994).

Sugar-Hormone Cross-Talk in Anthocyanin Biosynthesis

“…In Arabidopsis, CK is a positive regulator of the anthocyanin biosynthesis pathway and functions by modulating the expression of the anthocyanin biosynthesis genes PAL1, CHI, CHS and DFR (Deikman and Hammer, 1995). Transgenic plants overexpressing the isopentenyltransferase (IPT) gene, which is associated with CK biosynthesis, showed a greater accumulation of anthocyanin than wild-type plants in the presence of light and Suc (Guo et al, 2005).…”

The Jasmonate-ZIM-Domain Proteins Interact with the WD-Repeat/bHLH/MYB Complexes to Regulate Jasmonate-Mediated Anthocyanin Accumulation and Trichome Initiation inArabidopsis thaliana

“…Anthocyanin accumulation is stimulated by a series of endogenous developmental signals, such as Suc (Teng et al, 2005;Solfanelli et al, 2006) and plant hormones (Deikman and Hammer, 1995;Loreti et al, 2008;Shan et al, 2009), and by various environmental stresses, including UV irradiation, pathogen infection, insect attack, drought, wounding, and nutrient depletion (Harborne and Williams, 2000;Cominelli et al, 2008;Gonzalez et al, 2008;Lillo et al, 2008;Gonzalez, 2009).…”

MYB-related transcription factors function as regulators of the circadian clock and anthocyanin biosynthesis in Arabidopsis

“…24,25 Almost 2 decades ago, the expressions of the genes involved in anthocyanin biosynthesis, such as CHALCONE SYNTHASE (CHS), CHALCONE ISOMERASE (CHI), and DIHYDROFLA-VONOL 4-REDUCTASE (DFR), were found to be regulated by a circadian rhythm. 26 A number MYB transcription factors have been found to act as regulators of the flavonoid biosynthesis pathway. For example, MYB11, MYB12, MYB111, MYB75/ PAP1, and AtMYBD work as positive regulators whereas MYB-LIKE 2 (MYBL2) functions as a negative regulator.…”