Protein Phaseolin Research Articles

Physicochemical and functional properties of fermented pea and navy bean protein isolates

AbstractBackground and ObjectivesThere has been a significant increase in the use of fermentation for protein modification by the food industry. This research aimed to investigate the use of solid‐state fermentation (SSF) by Aspergillus oryzae NRRL 5590 on pea and navy bean protein isolates (PPI and NBPI, respectively) to enhance their physicochemical and functional properties.FindingsThe impact of fermentation was more profound on PPI than NBPI with a higher degree of hydrolysis achieved for the former (9.3% vs. 4.4%). Fermented PPI had significantly increased protein content, surface charge and hydrophobicity, solubility, and foaming properties, but decreased emulsion stability. For NBPI, modifications were only observed for surface hydrophobicity and water hydration capacity (WHC), which both increased after fermentation. Overall, navy bean proteins were less susceptible to protein hydrolysis than pea proteins upon fermentation, possibly due to the phaseolin protein in navy bean.ConclusionsIn summary, fermentation may be used to enhance the solubility and foaming properties of PPI and WHC of NBPI for their use as ingredients in applications where such higher functionalities are favorable.Significance and NoveltyThe results provide insights into pulse protein modification by bioprocessing, specifically fermentation, and opportunities for potential value‐added applications for pea and navy bean proteins.

Prevalence and Host Resistance to Common Bean Rust Disease in Western and Central Kenya

Rust, caused by Uromyces appendiculatus (Pers.) Unger, is among the most devastating diseases of the common bean (Phaseolus vulgaris L.) worldwide. The pathogen is highly genetically variable, causing severe epidemics under favourable weather conditions. The objectives of this study were to determine the distribution of bean rust in major production areas in Kenya and identify potential sources of resistance for breeding. A field survey was conducted in five counties targeting smallholder common bean farmers in western and central Kenya, where data on the incidence and severity of bean rust and crop management practices by farmers were recorded. Additionally, seeds of the evaluated genotypes were collected from farms visited for further testing. A total of 77 common bean genotypes were subjected to natural infection under field conditions and inoculated with races 29–1, 29–3, 61–1, and 63–1 of rust under greenhouse conditions at the University of Embu. The gene pool affiliation of the genotypes was determined through the phaseolin protein marker analysis. Rust incidence and severity data were subjected to an analysis of variance using GenStat statistical software. The results showed that bean rust occurred in all counties although there were significant differences ( P < 0.001 ) in incidence and severity among the surveyed localities. Based on a 1–9 severity rating scale, Bungoma County recorded the highest mean severity of 3.99 and an incidence of 71%. Cultivar grown, use of fungicides, management of residues, and crop spacing had a significant effect on bean rust severity. Under field and greenhouse conditions, the genotypes revealed high variations in response to rust, with 71% of the genotypes being susceptible under greenhouse inoculations. Enclave, MU#13, UN2-Darkgreen, UN6-Nakholo, Kat X56, and KMR-11 genotypes were identified as resistant and can be used as prospective parents in common bean improvement programs in Kenya. This study revealed high occurrence and distribution of common bean rust and thus provides critical baseline information for common bean rust management in Kenya.

Two γ-zeins induce the unfolded protein response.

The rapid, massive synthesis of storage proteins that occurs during seed development stresses endoplasmic reticulum (ER) homeostasis, which activates the ER unfolded protein response (UPR). However, how different storage proteins contribute to UPR is not clear. We analyzed vegetative tissues of transgenic Arabidopsis (Arabidopsis thaliana) plants constitutively expressing the common bean (Phaseolus vulgaris) soluble vacuolar storage protein PHASEOLIN (PHSL) or maize (Zea mays) prolamins (27-kDa γ-zein or 16-kDa γ-zein) that participate in forming insoluble protein bodies in the ER. We show that 16-kDa γ-zein significantly activates the INOSITOL REQUIRING ENZYME1/BASIC LEUCINE ZIPPER 60 (bZIP60) UPR branch-but not the bZIP28 branch or autophagy-leading to induction of major UPR-controlled genes that encode folding helpers that function inside the ER. Protein blot analysis of IMMUNOGLOBULIN-BINDING PROTEIN (BIP) 1 and 2, BIP3, GLUCOSE REGULATED PROTEIN 94 (GRP94), and ER-localized DNAJ family 3A (ERDJ3A) polypeptides confirmed their higher accumulation in the plant expressing 16-kDa γ-zein. Expression of 27-kDa γ-zein significantly induced only BIP3 and ERDJ3A transcription even though an increase in GRP94 and BIP1/2 polypeptides also occurred in this plant. These results indicate a significant but weaker effect of 27-kDa γ-zein compared to 16-kDa γ-zein, which corresponds with the higher availability of 16-kDa γ-zein for BIP binding, and indicates subtle protein-specific modulations of plant UPR. None of the analyzed genes was significantly induced by PHSL or by a mutated, soluble form of 27-kDa γ-zein that traffics along the secretory pathway. Such variability in UPR induction may have influenced the evolution of storage proteins with different tissue and subcellular localization.

The effects of blanching on composition and modification of proteins in navy beans (Phaseolus vulgaris)

Blanching is an important process in the preparation of navy beans (Phaseolus vulgaris L.) for canning. We here explore the effect of blanching which can profoundly affect protein composition and introduce protein-primary-level modifications. Amino acid analysis showed significantly decreased protein abundance (58.5%) in blanched beans compared to raw beans. Proteomic analyses revealed a decrease in high molecular weight isoforms of the major storage globulin proteins phaseolin (mean fold-change −3.7) and legumin (mean fold-change −2.5) and concomitant increase in their low molecular weight isoforms (mean fold-change 6.4 and 8.3, respectively). Blanched beans also had decreased abundance of lipoxygenase (mean fold-change −13.1), an enzyme responsible for product spoilage during storage. Increased lysinoalanine (up to 47%) and highly modified protein fragments were found in the processing waters, indicating heat- induced modifications. Correlating these molecular level changes thus provides a basis for evaluating how processing parameters can be modified to increase protein food quality.

English

French bean (Phaseolus vulgaris L.) is a major export crop in Kenya where it serves as a cash crop for smallholder farmers and a source of employment. However, there is limited information on characterization of available germplasm which is essential in genetic improvement of this crop. The present study was therefore aimed to identify the gene pool affiliations of Kenyan French bean germplasm using specific molecular markers in order to understand the available germplasm for future use in breeding programs. The germplasm panel consisted of 46 accessions, comprising 40 French bean and six dry bean genotypes. The accessions were characterized using four gel-based molecular markers: SHP1-A, SHP1-B, SHP1-C and phaseolin protein marker. The most informative marker was the phaseolin protein marker which indicated that 82% of the French bean genotypes are of Andean origin, while 18% are of the Mesoamerican origin. Low polymorphism was observed for the SHP1 markers and the data from the three SHP1 markers did not correspond to the phaseolin protein marker for the French bean germplasm although SHP1-A and SHP1-B were able to differentiate the Andean from the Mesoamerican differential cultivars. The information on the gene pool affiliations of Kenyan French bean accessions is important for breeders to harness the divergence between the two gene pools in order to broaden the genetic base of the crop.   Key words: Gene pool, phaseolin protein, shatterproof, molecular markers, French beans.

Analyzing bean extracts using time-dependent SDS trapping to quantify the kinetic stability of phaseolin proteins

In common beans and lima bean, the storage protein phaseolin is difficult to degrade and SDS-resistant, a sign of kinetic stability. Kinetically stable proteins (KSPs) are characterized by having a high-energy barrier between the native and denatured states that results in very slow unfolding. Such proteins are resistant to proteolytic degradation and detergents, such as SDS. Here the method SDS-Trapping of Proteins (S-TraP) is applied directly on bean extracts to quantify the kinetic stability of phaseolin in lima bean and several common beans, including black bean, navy bean, and small red bean. The bean extracts were incubated in SDS at various temperatures (60–75 °C) for different time periods, followed by SDS-PAGE analysis at room temperature, and subsequent band quantification to determine the kinetics of phaseolin unfolding. Eyring plot analysis showed that the phaseolin from each bean has high kinetic stability, with an SDS-trapping (i.e. unfolding) half-life ranging from about 20–100 years at 24 °C and 2–7 years at 37 °C. The remarkably high kinetic stability of these phaseolin proteins is consistent with the low digestibility of common beans and lima bean, as well as their relatively high germination temperatures. From a practical perspective, this work exemplifies that S-TraP is a useful and cost-effective method for quantifying the kinetic stability of proteins in biological extracts or lysates. Depending on the protein to be studied and its abundance, S-TraP may be performed directly on the extract without need for protein purification.

English

Angular leafspot (ALS), caused by the fungus, Pseudocercospora griseola, is one of the most important disease of common bean in Tanzania. Breeding for resistance to this disease is complicated by the variable nature of the pathogen. In Tanzania, a thorough analysis of the variability of this pathogen is lacking which limits breeding for durable resistance. This work aimed at characterizing P. griseola in relation to its host in Tanzania. A sample collection of both P. griseola and common bean was conducted in the 2013 and 2014 growing seasons from nine regions. Single spore isolation was performed for P. griseola isolates and DNA was extracted from both P. griseola mycelium and bean leaves from which the pathogen was collected. For characterization of the gene pool origin of the host, Phaseolin DNA marker was evaluated and for the pathogen, the Internal Transcribed Spacer region (ITS) and the Actin gene sequences were evaluated. Phylogenetic analysis showed the presence of 69.7% Andean and 30.3% Mesoamerican strains of P. griseola in Tanzania. The common bean host genotypes showed a similar distribution with 84.2% Andean and 15.8% Mesoamerican. In both cases, Andean strains of the pathogen and Andean bean genotypes outnumbered Mesoamerican. In relation to the common bean genotypes, Andean genotypes were more susceptible to ALS as compared to Mesoamerican genotypes. There were few strains that were of Andean origin but were pathogenic on Mesoamerican common bean genotypes, a group that has previously been termed Afro-Andean. Geographically, most of the regions of Tanzania had only Andean strains except for Kagera where 60% were Mesoamerican strains, and in Arusha and Tanga, where 50 and 33% were Mesoamerican, respectively. Only three regions, Kagera, Mbeya and Rukwa, were found to grow Mesoamerican beans. The findings of this study are important in setting basic objectives for breeding for angular leaf spot disease in Tanzania. Key words: Actin gene, angular leaf spot (ALS), Internal Transcribed Spacer region (ITS), Phaseolin protein, Phaseolus vulgaris.

Genetic Characterization of Green Bean (Phaseolus vulgaris L.) Accessions from Turkey with SCAR and SSR Markers.

Characterization, conservation, and utilization of genetic resources is essential for the sustainability in agriculture. Plant genetic resources are important for breeding efforts designed for the generation of new cultivars or for the improvement of existing ones. Green bean has been cultivated extensively in Turkey giving rise to local accessions through selection over time and adaptation to various environmental conditions. The objective of the present study was to determine the genetic relationships of green bean accessions collected from Kırşehir Province of Turkey, located at the central Anatolia. Within a population of 275 green bean accessions, 50 accessions were selected on the basis of morphological observations for further evaluation with SSR and STS/SCAR markers together with 4 reference cultivars of Andean and Mesoamerican origin. SSR markers selected on the basis of high polymorphism information content revealed the genetic relatedness of selected green bean accessions. STS/SCAR markers associated with bean anthracnose, common bacterial blight, white mold, halo blight, and phaseolin protein demonstrated the inheritance of resistance traits of local accessions at the selected loci. These findings may help better utilize genetic resources and furthermore are expected to facilitate forthcoming breeding studies for the generation of novel cultivars well adapted to the region.

Macronutrients and Micronutrients Profile of Some Underutilized Beans in South Western Nigeria

Beans are a rich source of nutrients in human diet. However a number of edible bean varieties are largely underutilized in developing countries due to little or no information on their nutritional composition. The present study investigated the nutritional content of mung beans, African yam beans, soybeans, black eyed peas and pigeon peas from parts of South Western Nigeria. Samples were collected randomly in duplicates across the six South - western states of Nigeria. Common beans was included as a reference for comparison. Standard methods were used to determine the proximate composition of all bean samples. Mineral nutrients and phaseolin protein fractions Original Research Article

Modified Bean Seed Protein Phaseolin Did Not Accumulate Stably in Transgenic Tobacco Seeds after Methionine Enhancement Mutations

The major seed storage protein phaseolin of common bean (Phaseolus vulgaris L.) is deficient in methionine, an essential amino acid for human and animal health. To improve the nutritional quality of common bean, we designed methionine enhancement of phaseolin based on the three-dimensional structure of protein, de novo design principles and genetic information. Amino acid substitution and loop insertion were targeted to the interior and exterior, respectively, of the protein’s β-barrels. First, we introduced the methionine enhancement mutations into phaseolin cDNA, expressed cDNA in Escherichia coli and purified monomeric non-glycosylated proteins. Biophysical analysis of E. coli-expressed proteins demonstrated a similar structural stability of wild-type and mutant phaseolin monomers. Here, we attempted to test the structural stability of the methionine-enhanced phaseolin by introducing phaseolin cDNA to tobacco via Agrobacterium tumefaciens-mediated transformation of leaf disks, regenerating transgenic tobacco plants, and examining the accumulation of phaseolin protein in mature transgenic tobacco seeds. We used seven constructs containing different extents of methionine enhancement, ranging from the original 3 to maximum 33 methionines per 397 amino acid residues. ELISA analyses indicated that the methionine-enhanced phaseolins did not accumulate as stably in mature transgenic tobacco seeds as the wild-type phaseolin. It seems likely that the methionine-enhanced phaseolin proteins were under the stringent scrutiny of the protein quality control mechanism in the endoplasmic reticulum (ER), Golgi complex and/or vacuolar protein bodies. The protein degradation is probably to occur in the vacuolar protein bodies due to the instability of the trimer assembly caused by the methionine enhancement mutations targeting either amino-acids substitutions or/and loop insertions to the interior β-sheets and tum/loop regions, respectively, of N- and C-barrel structures.

Evaluating two-dimensional electrophoresis profiles of the protein phaseolin as markers of genetic differentiation and seed protein quality in common bean (Phaseolus vulgaris L.).

High-resolution two-dimensional electrophoresis (2-DE) profiles of the protein phaseolin, the major seed storage protein of common bean, display great number of spots with differentially glycosylated and phosphorylated α- and β-type polypeptides. This work aims to test whether these complex profiles can be useful markers of genetic differentiation and seed protein quality in bean populations. The 2-DE phaseolin profile and the amino acid composition were examined in bean seeds from 18 domesticated and wild accessions belonging to the Mesoamerican and Andean gene pools. We found that proteomic distances based on 2-DE profiles were successful in identifying the accessions belonging to each gene pool and outliers distantly related. In addition, accessions identified as outliers from proteomic distances showed the highest levels of methionine content, an essential amino acid deficient in bean seeds. These findings suggest that 2-DE phaseolin profiles provide valuable information with potential of being used in common bean genetic improvement.

Trehalose‐containing hydrocolloid edible films prepared in the presence of transglutaminase

In this article, edible hydrocolloid films were prepared by using Citrus pectins and the protein phaseolin in the presence of microbial transglutaminase, an enzyme able to catalyze isopeptide bonds between endo-protein-reactive glutamine and lysine residues. For the first time, trehalose, a nonreducing homodisaccharide into which two glucose units are linked together by a α-1,1-glycosidic linkage, was used as a component of hydrocolloid films constituted of both proteins and carbohydrates. Our data have demonstrated that these films act as very effective barriers to gases, especially to CO2 . They also present a high antioxidant capability as measured by the 2,2-diphenyl-1-picrylhydrazyl scavenging assay. In addition, the films were characterized using Atomic Force Microscopy, a powerful tool used to evaluate film surface topography and roughness. The results of our experiments clearly indicate that the trehalose-containing films prepared both in the presence and absence of transglutaminase are composed of nanoparticles with a smooth surface, having similar roughness values (Rα). In conclusion, according to barrier and antioxidant properties and to their structure, it is possible to consider the trehalose-containing films as innovative bioplastics potentially able to protect different kinds of foods.

Characterization of Citrus pectin edible films containing transglutaminase-modified phaseolin

The growing social and economic consequences of pollution derived from plastics are focusing attention on the need to produce novel bioprocesses for enhancing food shelf-life. As a consequence, in recent years the use of edible films for food packaging is generating a huge scientific interest. In this work we report the production of an edible hydrocolloid film made by using Citrus pectin and the protein phaseolin crosslinked by microbial transglutaminase, an enzyme able to covalently modify proteins by formation of isopeptide bonds between glutamine and lysine residues. The films were characterized and their morphology was evaluated by both atomic force microscopy and scanning electron microscopy. Mechanical properties and barrier properties to CO2, O2 and water vapor have demonstrated that these films possess technological features comparable to those possessed by commercial plastics. It is worth noting that these characteristics are maintained even following storage of the films at 4°C or −20°C, suggesting that our bioplastics can be tailored to protect food at low temperature. Moreover, gastric and duodenal digestion studies conducted under the same conditions found in the human digestion system have demonstrated that transglutaminase-containing films are regularly digested encouraging an application of the proposed materials as food coatings.

Diversity and Population Structure of Common Bean from Brazil

ABSTRACTBrazil is arguably the world's largest bean producing country and the crop is an important cultural and nutritional component of food in this part of South America. Common bean (Phaseolus vulgaris L.) is cultivated in almost all Brazilian states by small and large producers in diverse production systems and holds great economic and social standing. The goal of this study was to evaluate a collection of 362 common bean landraces and cultivars from Brazil to determine the genetic diversity found in different regions of the country. We performed principal component and population structure analyses so as to understand the subgroups and races found in Brazil. The optimum number of subgroups in the Brazilian germplasm was found to be K = 5 and at this level, the Mesoamerican genepool was subdivided into four subgroups, which remained separate from the Andean subgroup (A1). The M2 and M3 subgroups presented high diversity and high levels of allele mixing between genepools. Subgroup and genepool identities were confirmed by morphological traits such as seed size and phaseolin protein types. Allele switching between the genepools was common for growth habits and phaseolin. The association of the subgroups with commercial classes of Brazilian beans (Carioca, Preto, Rosinha, and Roxinho Mesoamerican types or Jalo and Roxo Andean types) is discussed as is the potential for specific subraces among the germplasm in Brazil.

QUES, a new Phaseolus vulgaris genotype resistant to common bean weevils, contains the Arcelin-8 allele coding for new lectin-related variants

In common bean (Phaseolus vulgaris L.), the most abundant seed proteins are the storage protein phaseolin and the family of closely related APA proteins (arcelin, phytohemagglutinin and α-amylase inhibitor). High variation in APA protein composition has been described and the presence of arcelin (Arc) has been associated with bean resistance against two bruchid beetles, the bean weevil (Acanthoscelides obtectus Say) and the Mexican bean weevil (Zabrotes subfasciatus Bohemian). So far, seven Arc variants have been identified, all in wild accessions, however, only those containing Arc-4 were reported to be resistant to both species. Although many efforts have been made, a successful breeding of this genetic trait into cultivated genotypes has not yet been achieved. Here, we describe a newly collected wild accession (named QUES) and demonstrate its resistance to both A. obtectus and Z. subfasciatus. Immunological and proteomic analyses of QUES seed protein composition indicated the presence of new Arc and arcelin-like (ARL) polypeptides of about 30 and 27kDa, respectively. Sequencing of cDNAs coding for QUES APA proteins confirmed that this accession contains new APA variants, here referred to as Arc-8 and ARL-8. Moreover, bioinformatic analysis showed the two proteins are closely related to APA components present in the G12949 wild bean accession, which contains the Arc-4 variant. The presence of these new APA components, combined with the observations that they are poorly digested and remain very abundant in A. obtectus feces, so-called frass, suggest that the QUES APA locus is involved in the bruchid resistance. Moreover, molecular analysis indicated a lower complexity of the locus compared to that of G12949, suggesting that QUES should be considered a valuable source of resistance for further breeding purposes.

Antioxidant and metal chelating activities of Phaseolus vulgaris L. var. Jamapa protein isolates, phaseolin and lectin hydrolysates

A search in a database of potential bioactive short sequences in food proteins reveals that bioactive peptides with a variety of beneficial effects for cardiovascular health are present in the sequence of common bean proteins, including bioactive sequences with antioxidant properties. A protein isolate, the storage protein phaseolin and a lectin extract from Phaseolus vulgaris L. var. Jamapa, were hydrolyzed by treatment with pepsin and pancreatin in order to investigate the possible release of peptides with antioxidant and metal chelating properties. Antioxidant activity was determined in Caco-2 cells exposed to a free radical generator, and iron and copper chelating activities were determined using colorimetric methods. The highest antioxidant activity, 71% inhibition, was found in the hydrolyzed protein isolate. Copper and iron chelating activities were highest in the lectin and phaseolin hydrolysates, 53% and 81%, respectively. Thus, experimental data indicates, as suggested by the database search, that antioxidant peptides are abundant in pepsin–pancreatin hydrolysates, which may represent a valuable health-promoting property in common bean.

Determination of the N-glycosylation patterns of seed proteins: applications to determine the authenticity and substantial equivalence of genetically modified (GM) crops.

Methods have been developed to determine the N-glycosylation pattern of proteins at the single-seed level in two different biological systems. These were the well-characterized and widely consumed storage protein phaseolin from several species of Phaseolus (bean) and the α-amylase inhibitor from the same Phaseolus species expressed transgenically in pea. The N-glycosylation pattern of the α-amylase inhibitor expressed transgenically in pea was different from that of the inhibitor present in common bean (P. vulgaris), the species of origin of the gene. However, multivariate analysis showed that the differences in N-glycan patterns between the α-amylase inhibitors from common bean and pea were less than those between the inhibitors from common bean and two related bean species, lima bean (Phaseolus lunatus) and tepary bean (Phaseolus acutifolius).

Swelling, Mechanical, and Barrier Properties of Albedo-Based Films Prepared in the Presence of Phaseolin Cross-Linked or Not by Transglutaminase

Edible films were obtained from Citrus paradisi grapefruit albedo homogenates and bean protein phaseolin modified or not by the enzyme transglutaminase. Swelling capability, barrier performance to water vapor, oxygen and carbon dioxide, and mechanical properties of such films were investigated. The addition of the protein, mostly in the presence of transglutaminase, provide films less swellable at pH values above 5 compared to films made by albedo homogenates only, whereas the action of the enzyme clearly improves mechanical properties producing more stretchable and elastic films. Moreover, transglutaminase-mediated cross-linking of phaseolin gives rise to films less permeable to carbon dioxide and able to offer a high barrier to water vapor. These findings suggest that albedo-phaseolin film prepared in the presence of transglutaminase can be a promising candidate to be used as food edible wrap.

Trimeric glycoproteins of bean seed storage protein phaseolin were purified from baculovirus-infected insect Sf9 cells for use of structural study

We demonstrated here insect Sf9 cells provide a useful source of a large quantity of homogeneous plant protein to be used for further structural analysis by X-ray crystallography and other biophysical probes. The seed storage protein phaseolin accumulates in common bean ( Phaseolus vulgaris L.) as a trimeric glycoprotein in the vacuolar protein bodies of developing cotyledon. Here we characterized the post-translational modifications of phaseolin, glycosylation and trimer formation, after expression in Sf9 cells of fall armyworm ( Spodoptera frugiperda) infected by baculovirus. When a cDNA for the mature phaseolin protein (without its own signal peptide) was placed under control of the signal peptide of viral protein GP67 in baculovirus transfer vectors pAcGP67A, phaseolin accumulated within cells at a high level (40 μg/mL). To facilitate the protein purification, six histidines were added to the carboxyl terminal of phaseolin coding sequence as a metal-chelating affinity tag. Phaseolin was extracted from Sf9 cells by 6.0 M guanidinium chloride or 4.0 M urea as a protein solubilizing agent not as a denaturant, and purified by step-wise elution from a nickel column. Phaseolin was modified by a high-mannose glycan at two potential glycosylation-sties in insect Sf9 cells as demonstrated by digestion with endoglycosidase H or peptide N-glycosidase F. Asn 228 and Asn 317 of two potential glycosylation-sites were converted either singly or simultaneously to Glu by site-directed mutagenesis of the cDNA. Similar amounts of wild-type and glycosylation-minus mutants were purified from Sf9 cells. Analytical equilibrium centrifugation analysis demonstrated trimer formation of both wild-type and glycosylation-minus phaseolin. The results indicate that glycosylation is not required for the protein stability or trimer formation of phaseolin. When phaseolin was expressed under control of its own signal peptide in a second transfection vector pAcSG2, phaseolin was accumulated within cells similarly to the first constructs. However, elimination of two but not one glycosilation-sites resulted in the endoproteolytic cleavage(s) of the mature protein. Circular dichroism analysis indicated the proper secondary structure formation of phaseolin in insect Sf9 cells. Taken together, phaseolin was glycosylated, folded into the proper tertiary structure, and assembled into a trimer in insect Sf9 cells.

Protein markers and seed size variation in common bean segregating populations

Selection and random genetic drift are the two main forces affecting allele frequencies in common bean breeding programs. Therefore, knowledge on allele frequency changes attributable to these forces is of fundamental importance for breeders. The changes in frequencies of alleles of biochemical markers were examined in F2 to F7 populations derived from crosses between cultivated Mesoamerican and Andean common bean accessions (Phaseolus vulgaris L.). Biochemical markers included the seed proteins phaseolin, lectin and other seed polypeptides, and six isozymes. The Schaffer’s test detected a high significant linear trend of the 63% of the polymorphic loci studied, meaning that directional selection was acting on those loci. Associations between seed size traits, phaseolin seed-storage protein and isozyme markers were detected based on the comparisons of the progeny genotypic means. In the interracial populations the intermediate form PhaH/T, b6, and Rbcs98 alleles had a positive effect on seed size. In the inter-gene pool populations, a higher transmission of Mesoamerican alleles in all loci was showed, although the Andean alleles PhaT, Skdh100, Rbcs98, and Diap100 showed positive effects on seed weight. Our results suggest that phaseolin and other seed proteins markers are linked to loci affecting seed size. These markers have good potential for improving the results of the selection and should be considered as a strategy for germplasm enhancement and to avoid the reduced performance of the inter-gene pool populations.