Different Reactivity of Raw Starch from Diverse Potato Genotypes.

Potato starch is one of the most important renewable sources for industrial manufacturing of organic compounds. Currently, it is produced from mixed potato varieties that often are harvested from different fields. Meanwhile, tuber starches of various potato breeds differ in their crystallinity, granule morphology, and other physical and chemical parameters. We studied the reactions of raw potato starches of different origins to chemical and biochemical reactions typically used for industrial starch modification. The results clearly demonstrate that there is a significant difference in the reactivity of the starches of different potato genotypes. While the main products of the transformations are the same, their preparative yields differ significantly. Thus, tuber starch of certain potato varieties may be more suitable for specific industrial purposes. Starch reactivity may potentially be a phenotypical trait for potato breeding to obtain potato starches for various industrial applications.

Genetic loci determining potato starch yield and granule morphology revealed by genome-wide association study (GWAS).

BACKGROUND: It is well-documented that (bio)chemical reaction capacity of raw potato starch depends on crystallinity, morphology and other chemical and physical properties of starch granules, and these properties are closely related to gene functions. Preparative yield, amylose/amylopectin content, and phosphorylation of potato tuber starch are starch-related traits studied at the genetic level. In this paper, we perform a genome-wide association study using a 22K SNP potato array to identify for the first time genomic regions associated with starch granule morphology and to increase number of known genome loci associated with potato starch yield. METHODS: A set of 90 potato (Solanum tuberosum L.) varieties from the ICG "GenAgro" collection (Novosibirsk, Russia) was harvested, 90 samples of raw tuber starch were obtained, and DNA samples were isolated from the skin of the tubers. Morphology of potato tuber starch granules was evaluated by optical microscopy and subsequent computer image analysis. A set of 15,214 scorable SNPs was used for the genome-wide analysis. In total, 53 SNPs were found to be significantly associated with potato starch morphology traits (aspect ratio, roundness, circularity, and the first bicomponent) and starch yield-related traits. RESULTS: A total of 53 novel SNPs was identified on potato chromosomes 1, 2, 4, 5, 6, 7, 9, 11 and 12; these SNPs are associated with tuber starch preparative yield and granule morphology. Eight SNPs are situated close to each other on the chromosome 1 and 19 SNPs-on the chromosome 2, forming two DNA regions-potential QTLs, regulating aspect ratio and roundness of the starch granules. Thirty-seven of 53 SNPs are located in protein-coding regions. There are indications that granule shape may depend on starch phosphorylation processes. The GWD gene, which is known to regulate starch phosphorylation-dephosphorylation, participates in the regulation of a number of morphological traits, rather than one specific trait. Some significant SNPs are associated with membrane and plastid proteins, as well as DNA transcription and binding regulators. Other SNPs are related to low-molecular-weight metabolite synthesis, and may be associated with flavonoid biosynthesis and circadian rhythm-related metabolic processes. The preparative yield of tuber starch is a polygenic trait that is associated with a number of SNPs from various regions and chromosomes in the potato genome.

Starch phosphorylation associated SNPs found by genome-wide association studies in the potato (Solanum tuberosum L.).

BACKGROUND: The natural variation of starch phosphate content in potatoes has been previously reported. It is known that, in contrast to raw starch, commercially phosphorylated starch is more stable at high temperatures and shear rates and has higher water capacity. The genetic improvement of phosphate content in potato starch by selection or engineering would allow the production of phosphorylated starch in a natural, environmentally friendly way without chemicals. The aim of the current research is to identify genomic SNPs associated with starch phosphorylation by carrying out a genome-wide association study in potatoes. RESULTS: A total of 90 S. tuberosum L. varieties were used for phenotyping and genotyping. The phosphorus content of starch in 90 potato cultivars was measured and then statistically analysed. Principal component analysis (PCA) revealed that the third and eighth principal components appeared to be sensitive to variation in phosphorus content (p = 0.0005 and p = 0.002, respectively). PC3 showed the correlation of starch phosphorus content with allelic variations responsible for higher phosphorylation levels, found in four varieties. Similarly, PC8 indicated that hybrid 785/8-5 carried an allele associated with high phosphorus content, while the Impala and Red Scarlet varieties carried alleles for low phosphorus content. Genotyping was carried out using an Illumina 22 K SNP potato array. A total of 15,214 scorable SNPs (71.7% success rate) was revealed. GWAS mapping plots were obtained using TASSEL based on several statistical models, including general linear models (GLMs), with and without accounting for population structure, as well as MLM. A total of 17 significant SNPs was identified for phosphorus content in potato starch, 14 of which are assigned to 8 genomic regions on chromosomes 1, 4, 5, 7, 8, 10, and 11. Most of the SNPs identified belong to protein coding regions; however, their allelic variation was not associated with changes in protein structure or function. CONCLUSIONS: A total of 8 novel genomic regions possibly associated with starch phosphorylation on potato chromosomes 1, 4, 5, 7, 8, 10, and 11 was revealed. Further validation of the SNPs identified and the analysis of the surrounding genomic regions for candidate genes will allow better understanding of starch phosphorylation biochemistry. The most indicative SNPs may be useful for developing diagnostic markers to accelerate the breeding of potatoes with predetermined levels of starch phosphorylation.

Review of direct chemical and biochemical transformations of starch.

Starch is an important natural sustainable resource for various industries. Via chemical and biochemical one-step transformations it may be converted into numerous products or promising substances for different applications. All starch-based products may be divided into five main groups: carbon based materials, small organic molecules, starch depolymerization products, products with retained polymer chains but changed supramolecular structure, and modified starch. Some of the products are well-known and traditionally manufactured from starch in industrial scale. Other materials, like mesoporous carbon or nanosized starch particles, are just coming to market, and still require more thorough investigation and tuning of the preparation, treatment, and application procedures. Approaches for preparation of the novel greener composite or homogeneous carbon based materials, nanoparticles, heterocycles, organic acids, polyols from starch, are given in details. Recent improvements in starch hydrolysis, molecular or supramolecular modifications are also summarized in this review.

Interfacial surface properties of thiol-protected gold nanoparticles: a molecular probe EPR approach.

We present a molecular probe technique for accessing interfacial surface electrostatics of ligand-protected gold nanoparticles. A series of ligands with variable length of the hydrocarbon bridge between the anchoring sulfur and the reporting pH-sensitive nitroxide is described. The protonation state of this probe is directly observed by EPR spectroscopy. For tiopronin-protected Au nanoparticles, we observed an increase in pKa of up to ca. 1.1 pH units that was affected by the position of the reporter moiety with respect to the monolayer interface.

Solvent-controlled organization of self-assembled polymeric monolayers on gold: an easy approach for the construction of protein resistant surfaces.

Protein resistant surfaces based on poly(ethylene glycol) (PEG) coatings are extensively applied in the fields of biosensors, tissue engineering, fundamental cell-surface interaction research, and drug delivery systems. The structural organization of the PEG film on the surface has a significant effect on the performance of the film to resist protein adsorption. In this paper, we report an approach using solvent to control the organization of the polymeric monolayer on gold. A water soluble copolymer with grafted PEG side chains and alkyl disulfide side chains was synthesized. A polymeric monolayer was fabricated on a gold surface from different solutions (water- and toluene-based) of the copolymer. The organization of the polymeric monolayers was characterized by means of ellipsometry, cyclic voltammetry, contact angle, X-ray photoelectron spectroscopy, and atomic force microscopy. It was proven that the structural organization of the polymeric monolayer on a gold surface could be controlled by the solvent. A polymeric monolayer with PEG enriched at the outer level is obtained when water is used as the solvent. Various types of proteins, including fibrinogen, albumin, and normal human serum, were used to test the protein resistance of the gold surfaces modified by the polymeric monolayers. The polymeric monolayer formed from a water solution of the copolymer showed excellent protein resistance. In addition, by using water as the solvent, patterning of the polymeric monolayer could easily be achieved through a combination of lift-off and self-assembly. We believe that the approach reported here provides an easy, fast, and efficient way to fabricate a robust protein resistant surface.