Heterosis for horticultural traits in Broccoli

Over the last three decades, broccoli (Brassica oleracea L., Italica Group) hybrids made by crossing two inbred lines replaced open-pollinated populations to become the predominant type of cultivar. The change to hybrids evolved with little or no understanding of heterosis or hybrid vigor in this crop. Therefore, the purpose of the present study was to determine levels of heterosis expressed by a set of hybrids derived by crossing relatively elite, modern inbreds (n = 9). An additional objective was to determine if PCR-based marker derived genetic similarities among the parents can be useful to predict heterosis in this crop. Thirty-six hybrids derived from a diallel mating design involving nine parents were evaluated for five horticultural characters including the head characteristics of head weight, head stem diameter, and maturity (e.g., days from transplant to harvest), and the plant vigor characteristics of plant height, and plant width in four environments. A total of 409 polymorphic markers were generated by 24 AFLP, 23 SRAP and 17 SSR primer combinations. Euclidean distances between parents were determined based on phenotypic traits. About half of the hybrids exhibited highparent heterosis for head weight (1–30 g) and stem diameter (0.2–3.5 cm) when averaged across environments. Almost all hybrids showed highparent heterosis for plant height (1–10 cm) and width (2–13 cm). Unlike other traits, there was negative heterosis for maturity, indicating that heterosis for this character in hybrids is expressed as earliness. Genetic similarity estimates among the nine parental lines ranged from 0.43 to 0.71 and were significantly and negatively correlated with highparent heterosis for all traits except for stem diameter and days from transplant to harvest. Euclidean distances were not correlated with heterosis. With modern broccoli inbreds, less heterosis was observed for head characteristics than for traits that measured plant vigor. In addition, genetic similarity based on molecular markers was more highly correlated with plant vigor characteristics than head traits. Unlike with molecular marker-based estimates of genetic similarity, euclidean distance determined using phenotypic trait data was not predictive of heterosis. In conclusion, this study has documented heterosis in Brassica oleracea L., and the ability to predict heterosis in this crop using molecular marker-based estimates of genetic similarity among parents used in producing the hybrid. The contents of this publication do not necessarily reflect the views or policies of the USDA, nor does the mention of trade names, commercial products, or organizations imply endorsement by the US Government. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked as advertisement solely to indicate this fact.     

The defense response of germinating maize embryos against fungal infection: a proteomics approach

Pathogen attack on plants results in numerous host-specific biochemical responses, the activation of some of them being critical for the ability of the plant to withstand disease. We have used high-resolution two-dimensional gel electrophoresis (2-DE) and mass spectrometry to identify proteins that are differentially expressed in response to fungal infection in maize embryos. Differential spots corresponding to induced or repressed proteins were apparent in silver stained 2-DE gels of proteins extracted from sterile and fungal-infected germinating embryos. Selected spots were subjected to tryptic digestion followed by identification using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry and nanospray ion-trap tandem mass spectrometry. Among the proteins induced in response to infection are proteins involved in protein synthesis, or in protein folding and stabilization, as well as proteins involved in oxidative stress tolerance. Additionally, the accumulation of specific pathogenesis-related proteins in tissues of the fungal-infected germinating embryos was studied by 2-DE and immunoblotting.     

A proteomic analysis of leaf sheaths from rice

The proteins extracted from the leaf sheaths of rice seedlings were separated by 2-D PAGE, and analyzed by Edman sequencing and mass spectrometry, followed by database searching. Image analysis revealed 352 protein spots on 2-D PAGE after staining with Coomassie Brilliant Blue. The amino acid sequences of 44 of 84 proteins were determined; for 31 of these proteins, a clear function could be assigned, whereas for 12 proteins, no function could be assigned. Forty proteins did not yield amino acid sequence information, because they were N-terminally blocked, or the obtained sequences were too short and/or did not give unambiguous results. Fifty-nine proteins were analyzed by mass spectrometry; all of these proteins were identified by matching to the protein database. The amino acid sequences of 19 of 27 proteins analyzed by mass spectrometry were similar to the results of Edman sequencing. These results suggest that 2-D PAGE combined with Edman sequencing and mass spectrometry analysis can be effectively used to identify plant proteins.     

Comparative proteomic and phosphoproteomic analysis of the silkworm (Bombyx mori) posterior silk gland under high temperature treatment

The proteins from the posterior silk gland of silkworm hybrids and their parents reared under high temperatures were studied by using comparative proteomic and phosphoproteomic analysis. A total of 82.07, 6.17 and 11.76 % protein spots showed additivity, overdominance and underdominance patterns, respectively. Fifteen differentially expressed protein spots were identified by peptide mass fingerprinting. Among these, four spots, including sHSPs and prohibitin protein that were directly relevant to heat response, were identified. Eleven protein spots were found to play an important role in silk synthesis, and nine protein spots expressed phosphorylation states. According to Gene ontology and KEGG pathway analysis, these nine spots played an important role in stress-induced signal transduction. Expression of most silk synthesis-related proteins was reduced, whereas stress-responsive proteins increased with heat exposure time in three breeds. Furthermore, most proteins showed under- or overdominance in the hybrids compared to the parents. The results suggested that high temperature could alter the expression of proteins related to silk synthesis and heat response in silkworm. Moreover, differentially expressed proteins occurring in the hybrid and its parents may be the main explanation of the observed heterosis.     

Proteomic Analysis of Silk Viability in Maize Inbred Lines and Their Corresponding Hybrids

A long period of silk viability is critical for a good seed setting rate in maize (Zea mays L.), especially for inbred lines and hybrids with a long interval between anthesis and silking. To explore the molecular mechanism of silk viability and its heterosis, three inbred lines with different silk viability characteristics (Xun928, Lx9801, and Zong3) and their two hybrids (Xun928×Zong3 and Lx9801×Zong3) were analyzed at different developmental stages by a proteomic method. The differentially accumulated proteins were identified by mass spectrometry and classified into metabolism, protein biosynthesis and folding, signal transduction and hormone homeostasis, stress and defense responses, and cellular processes. Proteins involved in nutrient (methionine) and energy (ATP) supply, which support the pollen tube growth in the silk, were important for silk viability and its heterosis. The additive and dominant effects at a single locus, as well as complex epistatic interactions at two or more loci in metabolic pathways, were the primary contributors for mid-parent heterosis of silk viability. Additionally, the proteins involved in the metabolism of anthocyanins, which indirectly negatively regulate local hormone accumulation, were also important for the mid-parent heterosis of silk viability. These results also might imply the developmental dependence of heterosis, because many of the differentially accumulated proteins made distinct contributions to the heterosis of silk viability at specific developmental stages.     

Temporal Regulation of the Metabolome and Proteome in Photosynthetic and Photorespiratory Pathways Contributes to Maize Heterosis

Heterosis or hybrid vigor is widespread in plants and animals. Although the molecular basis for heterosis has been extensively studied, metabolic and proteomic contributions to heterosis remain elusive. Here we report an integrative analysis of time-series metabolome and proteome data in maize (Zea mays) hybrids and their inbred parents. Many maize metabolites and proteins are diurnally regulated, and many of these show nonadditive abundance in the hybrids, including key enzymes and metabolites involved in carbon assimilation. Compared with robust trait heterosis, metabolic heterosis is relatively mild. Interestingly, most amino acids display negative mid-parent heterosis (MPH), i.e., having lower values than the average of the parents, while sugars, alcohols, and nucleoside metabolites show positive MPH. From the network perspective, metabolites in the photosynthetic pathway show positive MPH, whereas metabolites in the photorespiratory pathway show negative MPH, which corresponds to nonadditive protein abundance and enzyme activities of key enzymes in the respective pathways in the hybrids. Moreover, diurnally expressed proteins that are upregulated in the hybrids are enriched in photosynthesis-related gene-ontology terms. Hybrids may more effectively remove toxic metabolites generated during photorespiration, and thus maintain higher photosynthetic efficiency. These metabolic and proteomic resources provide unique insight into heterosis and its utilization for high yielding maize and other crop plants.     

Heterosis of biomass production in Arabidopsis. Establishment during early development

Heterosis has been widely used in agriculture to increase yield and to broaden adaptability of hybrid varieties and is applied to an increasing number of crop species. We performed a systematic survey of the extent and degree of heterosis for dry biomass in 63 Arabidopsis accessions crossed to three reference lines (Col-0, C24, and Nd). We detected a high heritability (69%) for biomass production in Arabidopsis. Among the 169 crosses analyzed, 29 exhibited significant mid-parent-heterosis for shoot biomass. Furthermore, we analyzed two divergent accessions, C24 and Col-0, the F(1) hybrids of which were shown to exhibit hybrid vigor, in more detail. In the combination Col-0/C24, heterosis for biomass was enhanced at higher light intensities; we found 51% to 66% mid-parent-heterosis at low and intermediate light intensities (60 and 120 micromol m(-2) s(-1)), and 161% at high light intensity (240 micromol m(-2) s(-1)). While at the low and intermediate light intensities relative growth rates of the hybrids were higher only in the early developmental phase (0-15 d after sowing [DAS]), at high light intensity the hybrids showed increased relative growth rates over the entire vegetative phase (until 25 DAS). An important finding was the early onset of heterosis for biomass; in the cross Col-0/C24, differences between parental and hybrid lines in leaf size and dry shoot mass could be detected as early as 10 DAS. The widespread occurrence of heterosis in the model plant Arabidopsis opens the possibility to investigate the genetic basis of this phenomenon using the tools of genetical genomics.     

The regulatory network mediated by circadian clock genes is related to heterosis in rice

Exploitation of heterosis in rice(Oryza sativa L.) has contributed greatly to global food security.In this study,we generated three sets of reciprocal F1 hybrids of indica and japonica subspecies to evaluate the relationship between yield heterosis and the circadian clock.There were no differences in trait performance or heterosis between the reciprocal hybrids,indicating no maternal effects on heterosis.The indica-indica and indica-japonica reciprocal F1 hybrids exhibited pronounced heterosis for chlorophyll and starch content in leaves and for grain yield/biomass.In contrast,the japonica-japonica F1 hybrids showed low heterosis.The three circadian clock genes investigated expressed in an above-high-parent pattern(AHP)at seedling stage in all the hybrids.The five genes downstream of the circadian clock,and involved in chlorophyll and starch metabolic pathways,were expressed in AHP in hybrids with strong better-parent heterosis(BPH).Similarly,three of these Research Arfive genes in the japonica-japonica F1 hybrids showing low BPH were expressed in positive overdominance,but the other two genes were expressed in additive or negative overdominance.These results indicated that the expression patterns of circadian clock genes and their downstream genes are associated with heterosis,which suggests that the circadian rhythm pathway may be related to heterosis in rice.     

短乳杆菌DM9218核苷酸代谢过程中的蛋白组学分析

目的探讨短乳杆菌DM9218在核苷酸代谢过程中的蛋白表达差异。方法分别提取DM9218菌株与底物(肌苷+鸟苷)反应前后的菌体蛋白,利用蛋白双向凝胶电泳(2-DE)技术,找出该菌株与底物反应前后的差异蛋白质点,选取其中差异变化较大的蛋白点进一步做蛋白质谱分析。结果 2-DE分析显示两样品蛋白点主要分布在等电点4~9和分子量11~90 kD范围内,将所得的蛋白点结合其蛋白得率、浓度、储存蛋白含量进行比较,得到匹配的蛋白点数为732个。从中选取14个差异显著的蛋白点进行质谱分析,质谱结果显示所选取蛋白质点主要与物质代谢、能量转换及基因水平转录和翻译等生物学功能密切相关。结论本研究为后期分析研究短乳杆菌DM9218在核苷酸代谢过程中蛋白的表达奠定了基础。     

Absence of heterosis in hybrid corn. Description of the effect

Three unrelated homozygous maize lines, TS11, P22, and ST156, that produced hybrids in which heterosis was either absent or insignificant were identified. These hybrids were phenotypically similar to self-pollinated homozygous lines. Reciprocal crosses showed that the absence of heterosis is controlled by nuclear genes and is not associated with the cytoplasm of inbred lines. Analysis of F2 plants demonstrated that lines TS11, P22, and ST156 contained allelic genes determining the absence of heterosis in hybrid plants. Crosses of lines TS11, P22, and ST156 with a common selection line 092 generated hybrids with normal heterosis. It was concluded that heterozygosity or homozygosity of particular genes in lines TS11, P22, and ST156 play a pivotal role in the manifestation or the absence of hybrid vigor in hybrids.     

Differential protein expression in the cytosol fraction of an MCF-7 breast cancer cell line selected for resistance toward melphalan

Analysis of differential protein expression in the cytosol of melphalan-resistant and -susceptible MCF-7 cell lines has been carried out using a combination of two-dimensional gel electrophoresis, mass spectrometry, and bioinformatics. Comparison of multiple digitized gel arrays detected several spots as candidates for differentially expressed proteins in melphalan-resistant MCF-7 cells. The up-regulated proteins included retinoic acid binding protein II, an isoform of the macrophage migration inhibition factor, and other unidentified proteins. The down-regulated proteins included calreticulin, cyclophin A, and an isoform of the 27 kD heat shock protein. Correlation of the differential expression of some of the proteins with acquired resistance of MCF7 cells to melphalan is discussed.     

Hybrid vigor in cotton—Cytogenelic aspects and practical applications

The utilization of heterosis in first generation hybrids constitutes one of the more important contributions of plant breeding to agricultural production. Heterosis is pronounced in interspecific hybrids of Gossypium and is manifest in certain intraspecific crosses. The utilization of hybrid vigor in the commercial production of cotton is a current problem of much interest.     

Contributions of heterosis and epistasis to hybrid fitness

Early-generation hybrid fitness is difficult to interpret because heterosis can obscure the effects of hybrid breakdown. We used controlled reciprocal crosses and common garden experiments to distinguish between effects of heterosis and nuclear and cytonuclear epistasis among morphotypes and advanced-generation hybrid derivative populations in the Piriqueta caroliniana (Turneraceae) plant complex. Seed germination, growth, and sexual reproduction of first-generation hybrids, inbred parental lines, and outbred parental lines were compared under field conditions. Average vegetative performance was greater for hybrids than for inbred lines, and first-season growth was similar for hybrids and outbred parental lines. Hybrid survival surpassed that of inbred lines and was equal to or greater than outbred lines' survival, and more F(1) than parental plants reproduced. Reductions in hybrid fitness due to Dobzhansky-Muller incompatibilities (epistasis among divergent genetic elements) were expressed as differences in vegetative growth, survival, and reproduction between plants from reciprocal crosses for both F(1) and backcross hybrid generations. Comparing performance of hybrids against parental genotypes from intra- and interpopulation crosses allowed a more robust prediction of F(1) hybrids' success and more accurate interpretations of the genetic architecture of F(1) hybrid vigor.     

Analysis of the proteome in the human pituitary

The pituitary is the master endocrine gland responsible for the regulation of various physiologic and metabolic processes. Proteomics offers an efficient means for a comprehensive analysis of pituitary protein expression. This paper reports on the application of proteomics for the mapping of major proteins in a normal (control) pituitary. Pituitary proteins were separated by two-dimensional gel electrophoresis with immobilized pH 3-10 gradient strips. Major protein spots that were visualized in the two-dimensional gel by silver staining were excised, and the proteins in these spots were digested with trypsin. The tryptic digests were analyzed by mass spectrometry, and the mass spectrometric data were used to identify the proteins through searches of the SWISS-PROT or NCBInr protein sequence databases. The majority of the proteins were identified on the basis of peptide mass fingerprinting data obtained by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Several proteins were also characterized based on product-ion spectra measured by post-source decay analysis and/or liquid chromatography-electrospray-quadrupole ion trap mass spectrometry. To date, 62 prominent protein spots, corresponding to 38 different proteins, were identified. The identified proteins include important pituitary hormones, structural proteins, enzymes, and other proteins. The protein identification data were used to establish a two-dimensional reference database of the human pituitary, which can be accessed over the Internet (http://www.utmem.edu/proteomics). This database will serve as a tool for further proteomics studies of pituitary protein expression in health and disease.