Biology Photosynthesis Quiz - ThoughtCo
Flowering Plants, Shrubs and Trees
In Arabidopsis, light signaling is perceived and transduced by photoreceptors, including UV-B photoreceptor, cryptochrome 1 (CRY1) and phytochrome (PHY) A and B.– The plant transcription factors HY5 and PIF3 positively regulate anthocyanin biosynthesis through direct binding to the promoters of anthocyanin structural genes, including CHS, CHI, F3H, F3'H, DFR and LDOX. However, negative regulation of pigmentation by ethylene was shown to be independent of HY5. In addition to photoreceptors, photosynthesis also contributes to the formation of anthocyanin. In turnip seedlings and non-chlorophyllous corn leaf, light-dependent anthocyanin accumulation was significantly inhibited by treatment with diuron, 3-(3,4-dicrhlorophenyl)-1, 1-dimethylurea (DCMU), a photosynthetic inhibitor., Consistent with this, in Arabidopsis, DCMU treatment of seedlings suppressed the accumulation of anthocyanin pigmentation in photosynthetically active leaf tissues in wild-type Columbia seedlings (shown in ), as well as in the ethylene-insensitive mutant etr1-1. This suppression of anthocyanin accumulation was shown to be mediated through regulation of the transcription factors of the MYB-bHLH-WD40 (MBW) complex such as PAP1, Gl3 and EGL3. Additionally, there was an inverse relationship between the activity of the MBW complex and the level of MYBL2, which inhibits the formation of active MYB complexes. Ethylene maintains anthocyanin pigmentation in Arabidopsis leaves through the regulation of MYBL2 at the transcriptional level.
23/09/2008 · Why do leaves change color and turn red
A feature of anthocyanin pigmentation during development is the transient nature of accumulation when either environmental or developmental changes render the plant more sensitive to environmental conditions. Prolonged accumulation of anthocyanin occurs only in tissues that do not have a photosynthetic carbon assimilation function and is favorable only under conditions of high light or in an arid habitat. The effects of developmental and environmental factors on anthocyanin pigmentation have been extensively reviewed in reference . Plants have evolved such temporal and spatial regulation systems in part because the accumulation and maintenance of anthocyanin involves an investment of energy that may reduce light capture and eventually carbon assimilation., Hence, the regulation of anthocyanin pigmentation seems to be intimately connected to the universal phenomenon of overall homeostasis, wherein negative reciprocity between pathways ensures that anthocyanin is synthesized and greening is suppressed during early stages of seeding growth, when the seedlings are most susceptible to light stress. Anthocyanin suppression appears to be mediated in part through the desensitization of certain structural genes and/or negative regulation of other interrelated pathways., Thus, negative regulation of anthocyanin accumulation by ethylene might be a mechanism whereby the proper balance between carbon assimilation and anthocyanin accumulation is maintained in target tissues, via the suppression of light- and sugar-induced anthocyanin pigmentation. Such a view is supported by the observation that an increase in the level of ethylene in vivo is accompanied by an increase in sugar and light dosage.