Expression of an engineered granule-bound Escherichia coli glycogen branching enzyme in potato results in severe morphological changes in starch granules
Huang, X. ; Nazarian Firouzabadi, F. ; Vincken, J.P. ; Ji, Q. ; Suurs, L.C.J.M. ; Visser, R.G.F. ; Trindade, L.M. - \ 2013
Plant Biotechnology Journal 11 (2013)4. - ISSN 1467-7644 - p. 470 - 479.
binding domain - gene-expression - beta-amylase - freeze-thaw - amylose - biosynthesis - amylopectin - arabidopsis - synthase - protein
The Escherichia coli glycogen branching enzyme (GLGB) was fused to either the C- or N-terminus of a starch-binding domain (SBD) and expressed in two potato genetic backgrounds: the amylose-free mutant (amf) and an amylose-containing line (Kardal). Regardless of background or construct used, a large amount of GLGB/SBD fusion protein was accumulated inside the starch granules, however, without an increase in branching. The presence of GLGB/SBD fusion proteins resulted in altered morphology of the starch granules in both genetic backgrounds. In the amf genetic background, the starch granules showed both amalgamated granules and porous starch granules, whereas in Kardal background, the starch granules showed an irregular rough surface. The altered starch granules in both amf and Kardal backgrounds were visible from the initial stage of potato tuber development. High-throughput transcriptomic analysis showed that expression of GLGB/SBD fusion protein in potato tubers did not affect the expression level of most genes directly involved in the starch biosynthesis except for the up-regulation of a beta-amylase gene in Kardal background. The beta-amylase protein could be responsible for the degradation of the extra branches potentially introduced by GLGB.
Effects of germination on the activities of amylases and phenolic enzymes in sorghum varieties grouped according to food end-use properties
Dicko, M.H. ; Gruppen, H. ; Zouzouho, O.C. ; Traore, A.S. ; Berkel, W.J.H. van; Voragen, A.G.J. - \ 2006
Journal of the Science of Food and Agriculture 86 (2006)6. - ISSN 0022-5142 - p. 953 - 963.
phenylalanine ammonia-lyase - polyphenol oxidase - beta-amylase - cyanide contents - alpha-amylase - burkina-faso - peroxidase - cultivars - malt - viscosity
Fifty sorghum varieties were screened to determine the effects of germination on levels of starch, -amylase, -amylase, phenylalanine ammonia lyase (PAL), peroxidase (POX) and polyphenol oxidase (PPO). Germination decreased starch content, with amylose being more degraded than amylopectin. In germinated grain, -amylase activity increased several-fold in all varieties, whereas -amylase activity did not increase uniformly and even decreased in some varieties. Activity of the key enzyme in phenolic biosynthesis, PAL, was detected in only half of the varieties before germination but in all of them after germination. PPO was not activated in germinated sorghum grains, whereas POX activity increased up to tenfold in some varieties. Zymography revealed that germination induced de novo synthesis of several POX isoenzymes, among which an anionic POX isoenzyme (pI 3.1) was ubiquitously present. Amylase and phenolic enzyme activities could be correlated with grain and plant agronomic characteristics. The use of sorghum varieties for local dishes such as tô, dolo, couscous and thin porridge could be correlated with amylase and phenolic enzyme activities and the contents of their substrates. The biochemical constituents determined are useful markers for selection of varieties for food utilisation with special emphasis on infant porridges.
Sorghum grain as human food in Africa: relevance of content of starch and amylase activities
Dicko, M.H. ; Gruppen, H. ; Traore, A.S. ; Voragen, A.G.J. ; Berkel, W.J.H. van - \ 2006
African journal of biotechnology 5 (2006)5. - ISSN 1684-5315 - p. 384 - 395.
bicolor l moench - beta-amylase - alpha-amylase - kernel characteristics - protein digestibility - functional ingredient - chemical-composition - partial-purification - cultivated sorghum - fermented sorghum
Sorghum is a staple food grain in many semi-arid and tropic areas of the world, notably in Sub-Saharan Africa because of its good adaptation to hard environments and its good yield of production. Among important biochemical components for sorghum processing are levels of starch (amylose and amylopectin) and starch depolymerizing enzymes. Current research focus on identifying varieties meeting specific agricultural and food requirements from the great biodiversity of sorghums to insure food security. Results show that some sorghums are rich sources of micronutrients (minerals and vitamins) and macronutrients (carbohydrates, proteins and fat). Sorghum has a resistant starch, which makes it interesting for obese and diabetic people. In addition, sorghum may be an alternative food for people who are allergic to gluten. Malts of some sorghum varieties display a-amylase and ß-amylase activities comparable to those of barley, making them useful for various agro-industrial foods. The feature of sorghum as a food in developing as well as in developed countries is discussed. A particular emphasis is made on the impact of starch and starch degrading enzymes in the use of sorghum for some African foods, e.g. ¿tô¿, thin porridges for infants, granulated foods ¿couscous¿, local beer ¿dolo¿, as well agro-industrial foods such as lager beer and bread.
Sucrose-specific induction of anthocyanin biosynthesis in Arabidopsis requires the MYB75/PAP1 gene.
Teng, S. ; Keurentjes, J.J.B. ; Bentsink, L. ; Koornneef, M. ; Smeekens, S. - \ 2005
Plant Physiology 139 (2005)4. - ISSN 0032-0889 - p. 1840 - 1852.
transgenic tobacco plants - 3' untranslated region - vitis-vinifera - transcriptional regulation - flavonoid biosynthesis - signal-transduction - bhlh proteins - alpha-amylase - beta-amylase - expression
Sugar-induced anthocyanin accumulation has been observed in many plant species. We observed that sucrose (Suc) is the most effective inducer of anthocyanin biosynthesis in Arabidopsis (Arabidopsis thaliana) seedlings. Other sugars and osmotic controls are either less effective or ineffective. Analysis of Suc-induced anthocyanin accumulation in 43 Arabidopsis accessions shows that considerable natural variation exists for this trait. The Cape Verde Islands (Cvi) accession essentially does not respond to Suc, whereas Landsberg erecta is an intermediate responder. The existing Landsberg erecta/Cvi recombinant inbred line population was used in a quantitative trait loci analysis for Suc-induced anthocyanin accumulation (SIAA). A total of four quantitative trait loci for SIAA were identified in this way. The locus with the largest contribution to the trait, SIAA1, was fine mapped and using a candidate gene approach, it was shown that the MYB75/PAP1 gene encodes SIAA1. Genetic complementation studies and analysis of a laboratory-generated knockout mutation in this gene confirmed this conclusion. Suc, in a concentration-dependent way, induces MYB75/PAP1 mRNA accumulation. Moreover, MYB75/PAP1 is essential for the Suc-mediated expression of the dihydroflavonol reductase gene. The SIAA1 locus in Cvi probably is a weak or loss-of-function MYB75/PAP1 allele. The C24 accession similarly shows a very weak response to Suc-induced anthocyanin accumulation encoded by the same locus. Sequence analysis showed that the Cvi and C24 accessions harbor mutations both inside and downstream of the DNA-binding domain of the MYB75/PAP1 protein, which most likely result in loss of activity.