Genetic and developmental control of anthocyanin biosynthesis…
Cloning and expression analyses of R2R3-MYB genes related to anthocyanin biosynthesis in rose.
Genetic and developmental control of ..
Landsberg and Columbia wild-type plants responded differently to the limiting nitrogen condition. The decrease in biomass of Landsberg wild-type plants was more prominent than that of Columbia wild-type plants, suggesting that the Landsberg ecotype is more sensitive to the limiting nitrogen treatments used here. A similar pattern in growth variation was observed between different mutants under nitrogen limitation compared with non-stress growth conditions. Mutants in the later steps (tt3, tt7, and tt18) of the anthocyanin biosynthesis pathway were able to outperform those in the early steps (tt4 and tt5). The tt4 and tt5 plants once again accumulated less biomass—8.88mg and 5.92g, respectively—relative to the wild-type control (12.32g) under the limiting nitrogen condition at 24 DAG (). On the other hand, tt3, tt7, and tt18 mutants were able to accumulate slightly more biomass, compared with their respective wild-type controls grown under the limiting nitrogen condition. Early step anthocyanin biosynthesis mutants once again performed more poorly compared with the more downstream mutants, which is consistent with the finding under non-stress growth conditions (, ).
Making use of this large variety of genetic methods to manipulatethe formation and function of its nervous system, studies on have increased our knowledgeabout nervous development, plasticity including learning and memory formationand the control of sexually dimorphic complex interactive behaviours likecourtship and aggression.
Genetic and developmental control of anthocyanin biosynthesis
Despite its white flowers, the expression profiles of the eight genes in the RW hybrid were similar and even higher for , , and than those in the SC hybrid. Two notable features were that the expression level of was about 5-fold higher than those from the other hybrids and there was likely to be an interplay between the expression of and . On the basis of our results, the production of white flowers in the RW hybrid could possibly be explained by either or both of the following causes. First, 6 amino acid alterations in the conserved regions of F3H of the RW hybrid compared with those of the SE hybrid suggest a high potential for F3H functional alteration. This could result in the blockage of subsequent anthocyanin biosynthesis and the loss of color pigments (). Second, FLS catalyzes the production of colorless flavonols and competes with DFR in terms of anthocyanin production. Previous studies in white-flowered petunia containing high levels of flavonols demonstrated that the flower color could change from white to pink when either was down-regulated or was overexpressed (). Giving that the CHI2 function was disrupted by premature termination and expression was very low at early floral developmental stages, the level of the catalytic product of CHI could be very low in RW floral tissues. Thus, the white flowers of the RW hybrid could be the result of low expression levels of and high expression levels of , which cause the conversion of color flavonoid intermediates into colorless flavonols. To rule out these possibilities, further study of anthocyanin and flavonol compositions in RW flowers is required. If the RW hybrid exhibited white flowers because of CHI and/or F3H deficiencies, the accumulation of both anthocyanins and flavonols should be greatly reduced, whereas if this white flower phenotype is caused by the up-regulation of , the accumulation of flavonols should be increased and that of anthocyanins should be reduced.
Previous studies of anthocyanin contents suggested that the color intensity of flowers corresponded directly to pigment contents within the colored cells (). Considering the gene expression results, it is possible that the low color intensity in the SC hybrid could be because of the very low expression levels of and . The reduction in expression could, therefore, result in the low production of naringenin, downstream pigment production and color intensity, as a consequence.
Genetic and developmental control of anthocyanin biosynthesis ..
A clear difference in the growth rates of mutant lines in the first two committed steps of the anthocyanin production pathway compared with the subsequent steps was observed, as shown in . Whether under high light, limiting nitrogen, or non-stress conditions, upstream mutants tt4 and tt5 performed much more poorly compared with downstream mutants and wild-type control plants. The absence of anthocyanin production alone does not explain the drastic reduction in growth of the tt4 and tt5 plants given that other tt lines do not show such a decrease. The mutants in the early steps of the anthocyanin biosynthesis pathway are unable to synthesize most of the flavonoids, including kaempferol and quercetin. Kaempferol has been shown to accumulate to higher levels than other flavonoids under optimal growth conditions in Arabidopsis (). Plants are also known to accumulate quercetin, which is just downstream of kaempferol in the pathway, in response to nitrogen depletion (). Additionally, the ratio of kaempferol to quercetin changes in response to various environmental conditions (). These studies imply that flavonoid intermediates can have additional unknown functions in normal plant growth and response to environmental stresses. It is important to note that the mutant line lacking the flavanone 3-hydroxylase step (tt6) performed significantly better compared with tt4 and tt5 under non-stress and high light conditions. This mutation is leaky and these plants contain both kaempferol and some quercetin (). As such, the tt6 plants were able to grow on a par with tt7 and tt18 lines. Therefore, the absence of kaempferol and possibly quercetin leads to a dramatic decrease in biomass accumulation which is amplified under high light conditions.
Under limiting nitrogen conditions, the anthocyanin biosynthesis mutants were also found to display leaf yellowing during senescence. SAG12 expression confirmed the senescence rates in all of the lines tested. Based on these results, it was concluded that both anthocyanin production mutants and wild-type controls senesced at similar rates during the life cycle. Therefore, the leaf yellowing that was observed in the present experiments was an artefact of the absence of anthocyanin masking the regular process of chlorophyll degradation, as opposed to accelerated senescence as was originally suspected. It should also be noted that, despite differences in biomass accumulation, the tt lines and wild-type controls were at approximately the same developmental stages, as indicated by similar levels of SAG12 expression at 24 DAG.
Expression and mapping of anthocyanin biosynthesis genes in carrot
developmental control of anthocyanin biosynthesis.
id, isolation and characterization of tissue-specific differentially expressed genes for anthocyanin biosynthesis
Wei Zhang - Flinders University
Only a few reports of genetic control of anthocyanin biosynthesis are published for ..
Professor Centre for Marine Bioproducts Development
Comparison of HPLC Methods for Determination of Anthocyanins and Anthocyanidins in Bilberry Extracts
Tuscany Diet - Biochemistry and Nutrition
Reduction in expression of RbcS and CAB1 genes is associated with reduced photosynthetic activity as plants senesce (; ). In addition, these genes serve as markers for the normal limiting nitrogen response (). In order to provide additional support for the chlorophyll content observation, expression levels of CAB1 and RbcS were measured by qRT-PCR. Levels of CAB1 and RbcS transcript in almost all of the anthocyanin production mutants were nearly equal to those of wild-type controls at both time points (). Therefore, the limiting nitrogen response of plants at both molecular genetic and physiological levels was not affected by the presence of anthocyanin and/or a varying flavonoid profile.
The Regional Institute - Publications
Significantly larger differences in biomass accumulation between mutant lines in the first two steps of the anthocyanin biosynthesis pathway (tt4 and tt5) and the mutant lines in the subsequent steps (tt6, tt7, tt3, and tt18) under high light compared with the other growth conditions tested were observed (). Mutants defective in the first two steps of the anthocyanin production pathway (tt4 and tt5) accumulated 11.9mg and 5.2mg, respectively, compared with 30.9mg for the wild-type control plants. On the other hand, the remaining lines were equal to or performed slightly better than the wild-type control. Two downstream mutant lines, tt6 and tt7, showed a significant increase in biomass accumulation compared with the wild-type control under high light conditions. The difference in biomass accumulation in tt18 plants relative to the wild-type control under high light treatment was not significant. Due to growth differences between Landsberg and Columbia ecotypes under certain conditions, the anthocyanin production mutants were only compared with their respective wild-type controls (, ).
All Issues - Horticultural Science & Technology
The importance of anthocyanin production is evident even under non-stress growth conditions where, on average, all anthocyanin production mutants performed more poorly compared with wild-type controls (). The knockout lines at various steps in the anthocyanin production pathway were examined to investigate whether changes in the growth rate were due to lack of anthocyanin or overaccumulation of flavonoid intermediates. Mutants defective in early steps in the pathway (tt4 and tt5) that do not produce most of the flavonoid intermediates had a significantly negative effect on biomass accumulation at 24 DAG (). This suggests that downstream flavonoids could be playing a role in normal plant growth and development. While mutants defective in later stages of the pathway (tt6, tt7, tt3, and tt18) performed better than early mutants by comparison, they consistently had between 11% and 34% lower biomass accumulation than wild-type plants at this time point depending on the mutant line tested. Therefore, inability to produce flavonoids has a negative effect on plant growth and/or development.
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