Browsing by Subject "Anthocyanin"
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Item AtSUC1 ROOT EXPRESSION AND SUCROSE RESPONSE LEADING TO ANTHOCYANIN ACCUMULATION(2019-12) Lasin, PraphapanPrevious research indicated that AtSUC1 root expression is controlled by intragenic sequences. The 5’ upstream region (promoter) of AtSUC1 directs pollen and trichome expression, but not root expression. However, the whole AtSUC1 gene can drive root expression and sucrose-induced root expression. Here I show that root expression of AtSUC1 is controlled by the interaction between the promoter and its two short introns. Deletion of either intron from whole-gene-GUS constructs resulted in no root expression, showing that both introns are required. The two introns in tandem, fused to GUS, produce high constitutive expression throughout the vegetative parts of the plant. When combined with the promoter, the expression driven by the introns is reduced and localized to the roots. AtSUC1 expression is also induced by exogenous sucrose, and AtSUC1 is also required for sucrose-induced anthocyanins (Sivitz et al., 2008). Anthocyanin accumulation due to high sucrose was lesser in the AtSUC1 mutant compared to Col-0 wild type. A whole-gene-GUS construct expressing a non-functional AtSUC1 (D152N) mutant, that is transport inactive, was defective in sucrose-induced AtSUC1 expression and anthocyanins accumulation when expressed in an atsuc1-null background. The results indicated that sucrose uptake via AtSUC1 is required for sucrose-induced AtSUC1 expression and anthocyanin accumulation, and that the site for sucrose detection is intracellular.Item Coordination of Phloem Function and Anthocyanin Accumulation in Senescing Leaves of Quercus rubra(2023-11) Rooney, RebeccaAutumnal senescence is an important annual occurrence for many deciduous temperate species, as it is the final period for plants to regain limiting nutrients from leaf tissue. Effective remobilization requires efficient breakdown of cellular components and translocation into perennating tissues via the phloem, a vascular tissue primarily responsible for the transport of photoassimilates. Anthocyanins are a pigment that accumulate in some species during senescence and are hypothesized to confer a photoprotective role in senescing leaves. Anthocyanin biosynthesis is regulated, in part, by sugar signaling, and girdling studies have linked phloem to anthocyanin accumulation to the augmentation of sugar concentrations in leaf tissue. While these studies show that halted translocation is associated with anthocyanin biosynthesis, natural changes in the phloem during autumnal senescence have yet to be examined with respect to anthocyanin. Here I elucidate how changes in phloem function (e.g., leaf carbon export and callose deposition) corresponds to soluble sugars and anthocyanin buildup in leaf tissue during senescence. I found that while phloem function declined throughout senescence, soluble sugars did not accumulate in leaf tissue. Despite this, anthocyanin content did significantly increase by the end of the season. Carbon export did not correlate to anthocyanin buildup or callose deposition. Instead, carbon export corresponded to changes in the proportions of leaf soluble sugars, while anthocyanic leaves were associated with higher fructose concentrations. My results indicate that soluble sugars are involved in multiple processes in senescing leaves and their relationship to anthocyanin and phloem is nuanced. This study provides insight into how phloem function declines during senescence, while prompting further studies into the regulation of phloem transport and how changes in this system may impact other leaf functions during autumnal senescence.Item Studies on apple peel color regulation.(2009-05) Rabinovich, Adriana TeliasOne of the most important factors determining apple [Malus pumila P. Mill.] market acceptance is peel color. Most apple cultivars (e.g. `Royal Gala') produce fruit with a defined fruit pigment pattern, but in the case of `Honeycrisp' apple, trees can produce fruits of two different kinds: striped and blushed. The causes of this phenomenon are unknown. We compared 'Honeycrisp' fruit from trees that were propagated from buds occurring on branches carrying only blushed or only striped fruit and concluded that blushed trees tend to produce a higher percentage of blushed fruit than striped trees, indicating a mechanism conserved through cell division. The percentage of blushed fruit on any given tree changed from year to year. Blushed and striped fruit occurred together on the same branch, and even on the same spur, with fruits located in the outer canopy being more likely to be striped. Higher crop loads were associated with a lower percentage of blushed fruit on the tree. Blushed and striped fruit do not consistently differ in their maximum pigment accumulation before ripening. The comparison of average hue angle for the whole peel at harvest indicates that blushed fruit are redder on average. We have also shown that striped areas of `Honeycrisp' and `Royal Gala' are due to sectorial increases in anthocyanin concentration. Transcript levels of the major biosynthetic genes and MdMYB10, a transcription factor that upregulates apple anthocyanin production, correlated with increased anthocyanin concentration in stripes. However, changes in the promoter and coding sequence of MdMYB10 do not correlate with skin pattern in `Honeycrisp' and other cultivars differing in peel pigmentation patterns. A survey of methylation levels throughout the coding region of MdMYB10 and a 2.5 kb region 5' of the ATG translation start site indicated that an area 900 bp long, starting 1400 bp upstream of the translation start site, is highly methylated. Comparisons of methylation levels of red and green stripes indicated that the degree of methylation of the MdMYB10 promoter is likely to be associated with the presence of stripes in these cultivars, with red stripes having lower methylation levels. Methylation may be associated with the presence of a TRIM retrotransposon within the promoter region, but the presence of the TRIM element alone cannot explain the phenotypic variability observed in `Honeycrisp'. We suggest that methylation in the MdMYB10 promoter is more variable in `Honeycrisp' than in `Royal Gala', leading to more variable color patterns in the peel of this cultivar.