Yongbin Dong

Verification of QTL for grain starch content and its genetic correlation with oil content using two connected RIL populations in high-oil maize.

Grain oil content is negatively correlated with starch content in maize in general. In this study, 282 and 263 recombinant inbred lines (RIL) developed from two crosses between one high-oil maize inbred and two normal dent maize inbreds were evaluated for grain starch content and its correlation with oil content under four environments. Single-trait QTL for starch content in single-population and joint-population analysis, and multiple-trait QTL for both starch and oil content were detected, and compared with the result obtained in the two related F2∶3 populations. Totally, 20 single-population QTL for grain starch content were detected. No QTL was simultaneously detected across all ten cases. QTL at bins 5.03 and 9.03 were all detected in both populations and in 4 and 5 cases, respectively. Only 2 of the 16 joint-population QTL had significant effects in both populations. Three single-population QTL and 8 joint-population QTL at bins 1.03, 1.04–1.05, 3.05, 8.04–8.05, 9.03, and 9.05 could be considered as fine-mapped. Common QTL across F2∶3 and RIL generations were observed at bins 5.04, 8.04 and 8.05 in population 1 (Pop.1), and at bin 5.03 in population 2 (Pop.2). QTL at bins 3.02–3.03, 3.05, 8.04–8.05 and 9.03 should be focused in high-starch maize breeding. In multiple-trait QTL analysis, 17 starch-oil QTL were detected, 10 in Pop.1 and 7 in Pop.2. And 22 single-trait QTL failed to show significance in multiple-trait analysis, 13 QTL for starch content and 9 QTL for oil content. However, QTL at bins 1.03, 6.03–6.04 and 8.03–8.04 might increase grain starch content and/or grain oil content without reduction in another trait. Further research should be conducted to validate the effect of these QTL in the simultaneous improvement of grain starch and oil content in maize.

Isolation and characterization of ZmERF1 encoding ethylene responsive factor-like protein 1 in popcorn (Zea mays L.)

AbstractThe ethylene response factor (ERF) plays a key role in the transcriptional regulation of plant growth, development, and response to various environmental perturbations. Study of ERF transcription factors, especially those in cultivated crops, could facilitate their molecular genetic modification. In this study, an ERF1 gene, designated as ZmERF1, which was found to be localized in the nucleus, was isolated from popcorn (Zea mays L.). Further analysis showed that the ZmERF1 proteins could bind to the GCC box motif and act as a transcriptional activator. A clear picture of ZmERF1 expression pattern showed that ZmERF1 expression varies during different development stages of endosperm. Furthermore, its expression could be highly induced by salinity, osmotic and heat stress, suggesting that the gene is involved in stress signaling pathways in maize. Therefore, ZmERF1 could play important role in abiotic stress tolerance and endosperm development in maize.

Dynamic Proteomic Characteristics and Network Integration Revealing Key Proteins for Two Kernel Tissue Developments in Popcorn

The formation and development of maize kernel is a complex dynamic physiological and biochemical process that involves the temporal and spatial expression of many proteins and the regulation of metabolic pathways. In this study, the protein profiles of the endosperm and pericarp at three important developmental stages were analyzed by isobaric tags for relative and absolute quantification (iTRAQ) labeling coupled with LC-MS/MS in popcorn inbred N04. Comparative quantitative proteomic analyses among developmental stages and between tissues were performed, and the protein networks were integrated. A total of 6,876 proteins were identified, of which 1,396 were nonredundant. Specific proteins and different expression patterns were observed across developmental stages and tissues. The functional annotation of the identified proteins revealed the importance of metabolic and cellular processes, and binding and catalytic activities for the development of the tissues. The whole, endosperm-specific and pericarp-specific protein networks integrated 125, 9 and 77 proteins, respectively, which were involved in 54 KEGG pathways and reflected their complex metabolic interactions. Confirmation for the iTRAQ endosperm proteins by two-dimensional gel electrophoresis showed that 44.44% proteins were commonly found. However, the concordance between mRNA level and the protein abundance varied across different proteins, stages, tissues and inbred lines, according to the gene cloning and expression analyses of four relevant proteins with important functions and different expression levels. But the result by western blot showed their same expression tendency for the four proteins as by iTRAQ. These results could provide new insights into the developmental mechanisms of endosperm and pericarp, and grain formation in maize.

Integrative detection and verification of QTL for plant traits in two connected RIL populations of high-oil maize

Plant traits play an important role in determining plant density and final grain yield. In this study, two related RIL populations developed from two crosses between one high-oil maize inbred and two normal dent maize inbreds were evaluated for 13 plant traits under four environments. QTL were detected within population and in joint-population analysis, and compared with the result obtained in the two F2:3 generations. Our main objective was to find identical QTL and key genetic regions valuable in further research. Totally, 318 single-population QTL, 142 pairs of digenic epistasis and 412 joint-population QTL were detected. Joint-population analysis could detect much more QTL and increase the accuracy of QTL localization. Consistent QTL across generations, environments and analysis methods were observed for five traits at four bins. QTL for plant height and ear height at bin 3.05, and for leaf area at bin 6.03–6.04 had the highest consistency across most situations. These QTL with high consistency were worthy to be put into marker-assisted selection in trait improvement and to construct near isogenic lines in further research. Maize breeding could be improved by integrating marker assisted selection and phenotypic selection.

A maize ADP-ribosylation factor ZmArf2 increases organ and seed size by promoting cell expansion in Arabidopsis

ADP-ribosylation factors (ARFs) are small GTP-binding proteins that regulate a wide variety of cell functions. Previously, we isolated a new ARF, ZmArf2, from maize (Zea mays). Sequence and expression characteristics indicated that ZmArf2 might play a critical role in the early stages of endosperm development. In this study, we investigated ZmArf2 function by analysis of its GTP-binding activity and subcellular localization. We also over-expressed ZmArf2 in Arabidopsis and measured organ and cell size and counted cell numbers. The expression levels of five organ size-associated genes were also determined in 35S::ZmArf2 transgenic and wild-type plants. Results showed that the recombinant ZmArf2 protein purified from Escherichia coli exhibited GTP-binding activity. Subcellular localization revealed that ZmArf2 was localized in the cytoplasm and plasma membrane. ZmArf2 over-expression in Arabidopsis showed that 35S::ZmArf2 transgenic plants were taller and had larger leaves and seeds compared to wild-type plants, which resulted from cell expansions, not an increase in cell numbers. In addition, three cell expansion-related genes, AtEXP3, AtEXP5 and AtEXP10, were upregulated in 35S::ZmArf2 transgenic lines, while the expression levels of AtGIF1 and AtGRF5, were unchanged. Collectively, our studies suggest that ZmArf2 has an active GTP-binding function, and plays a crucial role in growth and development in Arabidopsis through cell expansion mediated by cell expansion genes.

QTL consistency for agronomic traits across three generations and potential applications in popcorn

Abstract Favorable agronomic traits are important to improve productivity of popcorn. In this study, a recombinant inbred line (RIL) population consisting of 258 lines was evaluated to identify quantitative trait loci (QTLs) for nine agronomic traits (plant height, ear height, top height (plant height subtracted ear height), top height/plant height, number of leaves above the top ear, leaf area, stalk diameter, number of tassel branches and the length of tassel) under three environments. Meta-analysis was conducted then to integrate QTLs identified across three generations (RIL, F2:3 and BC2F2) developed from the same crosses. In total, 179 QTLs and 36 meta-QTLs (mQTL) were identified. The percentage of phenotypic variation (R2) explained by any single QTL varied from 3.86 to 28.4%, and 24 QTLs with contributions over 15%. Nine common QTLs located in the same or similar chromosome regions were detected across three generations. Five meta-QTLs were identified including QTLs in three independent studies. Seven important mQTLs were composed of 11–26 QTLs for 4–7 traits, respectively. Only 11 mQTLs were commonly identified in the same or similar chromosome regions across agronomic traits, popping characteristics (popping fold, popping volume and popping rate) and grain yield components (ear weight per plant, grain weight per plant, 100-grain weight, ear length, kernel number per row, ear diameter, row number per ear and kernel ratio) by meta-QTL analysis. In conclusion, we identified a list of QTLs, some of which with much higher contributions to agronomic traits should be valuable for further study in improving both popping characteristics and grain yield components in popcorn.

QTL identification and meta-analysis for kernel composition traits across three generations in popcorn

Abstract Dissecting the genetic controls of kernel composition traits would provide important information for improving popcorn’s quality. In this research, a recombinant inbred lines (RILs) population with 258 RILs was evaluated to detect quantitative trait loci (QTLs) for 4 kernel composition traits (CT, starch concentration; CP, protein concentration; CF, oil concentration; LS, lysine concentration) under three environments. As a result, 23 QTLs associated with the 4 kernel component traits were identified. Four QTLs at bins 3.04, 3.04, 4.01 and 5.03–5.04 were consistently detected in the similar chromosome locations. Three QTLs at bins 1.07–1.08, 3.04 and 6.07 were commonly detected in the same or nearby bins across three generations (RIL, F2:3 and BC2F2) derived from the same cross. A meta-analysis was conducted to integrate QTLs detected across three generations. Fifteen meta-QTLs were detected except on chromosomes 8 and 10. Three chromosome locations (bins 3.04, 4.01 and 5.03–5.04) with higher contribution to kernel composition traits showed no relation with the QTLs identified for popping characteristics. Three chromosomal regions could be further used to improve of maize kernel quality and to enhance popcorn quality.

QTL Detection for Grain Water Relations and Genetic Correlations withGrain Matter Accumulation at Four Stages after Pollination in Maize

Grain water relations were closely correlated with matter accumulation during grain development. In this study, QTL mapping for Grain Water Content (GWC) at four stages after pollination and Grain Dehydration Rate (GDR) during six intervals were done using 258 Recombinant Inbred Lines (RIL). Meta-QTL (mQTL) was revealed by meta-analysis using Bio Mercator for both traits herein and together with seven traits related with grain matter accumulation in our previous research. Among 40 QTL detected for GWC and 35 QTL for GDR, 45 QTL were stage/period specific. QTL on chromosome 5 could be considered as full-stage QTL. Eight of 11 mQTL included QTL for both traits. Grain matter traits were positively correlated with GWC, but negatively correlated with GDR in most cases. Low coincidences in QTL position and opposite allelic effects for two kinds of traits suggested that their simultaneous improvement might be realized. Selection for low grain moisture could be focused on QTL at bins 1.07- 1.08, 2.08, 4.03-4.04 and 5.03-5.04, while it should be followed to QTL at bins 7.02-7.03, 1.03-1.04 and 10.05-10.06 for high grain weight. However, this should be proved through practical selection, and the related marker intervals needed to be narrowed down in further research.

iTRAQ-Based Proteomics Analysis and Network Integration for Kernel Tissue Development in Maize

Grain weight is one of the most important yield components and a developmentally complex structure comprised of two major compartments (endosperm and pericarp) in maize (Zea mays L.), however, very little is known concerning the coordinated accumulation of the numerous proteins involved. Herein, we used isobaric tags for relative and absolute quantitation (iTRAQ)-based comparative proteomic method to analyze the characteristics of dynamic proteomics for endosperm and pericarp during grain development. Totally, 9539 proteins were identified for both components at four development stages, among which 1401 proteins were non-redundant, 232 proteins were specific in pericarp and 153 proteins were specific in endosperm. A functional annotation of the identified proteins revealed the importance of metabolic and cellular processes, and binding and catalytic activities for the tissue development. Three and 76 proteins involved in 49 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were integrated for the specific endosperm and pericarp proteins, respectively, reflecting their complex metabolic interactions. In addition, four proteins with important functions and different expression levels were chosen for gene cloning and expression analysis. Different concordance between mRNA level and the protein abundance was observed across different proteins, stages, and tissues as in previous research. These results could provide useful message for understanding the developmental mechanisms in grain development in maize.

Characterization of a maize ERF gene, ZmERF1, in hormone and stress responses

ERFs are downstream component in ethylene signaling pathway and involved in plant’s abiotic stress response. The specific role of ERFs under stress and the molecular mechanism underlying the signaling cross talk still need to be elucidated. This study describes the isolation and characterization of ZmERF1 promoter. There were many cis-regulatory elements related to stress responses in the ZmERF1 promoter sequence. ZmERF1 could be highly induced by ABA and ethylene treatment in maize, suggesting that it might be at the crossroads of multiple hormone signaling pathways. Furthermore, ZmERF1 transgenic Arabidopsis lines (35S::ZmERF1) showed higher salt-tolerant, drought- and heat resistance. Consistently, tolerance-related genes were up-regulated in 35S::ZmERF1 lines compared with the WT plants in Arabidopsis. Overall, ZmERF1 might play an important role in plant resistance to a coercive environment by mediating various physiological processes via ethylene and ABA signaling pathways.