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  • Author or Editor: Fang Xiao x
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Sucrose synthase (SS) is one of the key enzymes in plant carbohydrate metabolism. In maize, this enzyme is encoded by two genes, Sh1 and Sus1. We have isolated and determined the 5'-upstream sequence of maize Sus1 gene and compared it with the corresponding sequence in Sh1 gene. Sequence analysis revealed that there was a weak homology between the two promoters and no common sequence elements were found. To understand the differential regulation of the expression of the two genes, we constructed chimeric GUS fusions using the two promoters of SS genes. By using the biolistic system, we delivered these constructs into various plant tissues, and their transient expression was studied. Our results showed that the two promoters of SS genes directed tissue-specific expression in the same way that the two genes are expressed in vivo. The effectiveness of the expression of the constructs was recorded by counting the total blue expression units (blue spots) per shot and by fluorometric assays. High levels of GUS activity were detected in the immature embryos, young coleoptiles, and heterotrophic young leaves bombarded with the Sus–GUS construct. More than 100 expression units were observed in these tissues. Compared with the transient expression of the 35S promoter in the same tissue, Sus promoter activity was twice as high. Strong Sus–GUS expression was also detected in the aleurone cells of developing kernels. In contrast, the Sh-GUS construct was expressed only in the endosperm with an activity twice as high as that of Sus–GUS and 35S–GUS in the same tissue. The results will be discussed in terms of the physiological roles of the two SS isozymes in plant tissues.

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The characterization of aroma of the 14 main apricot (Prunus armeniaca L.) cultivars in Xinjiang was evaluated using high-performance solid-phase microextraction (HP-SPME) with gas chromatography-mass spectroscopy (GC-MS). A total of 208 volatiles that include 80 esters, 25 aldehydes, 15 terpenes, 21 ketones, 39 alcohols, 27 olefins, and 1 acid were identified from these cultivars. The compounds propyl acetate, 3-methyl-1-butanol acetate, (Z)-3-hexen-1-ol acetate, d-limonene, β-linalool, hexanal, hexyl acetate, butyl acetate, β-myrcene, ethyl butanoate, and β-cis-ocimene were the major compounds responsible for aroma in these cultivars. GC-MS results showed that Kuchexiaobaixing, Guoxiyuluke, and seven other cultivars were characterized by a high level of esters and were considered to be fruity apricot aroma. ‘Luotuohuang’ and ‘Heiyexing’ accumulate high levels of terpenes and exhibited an outstanding floral aroma. Higher levels of alcohols and aldehydes were observed in ‘Danxing’, ‘Sumaiti’, and ‘Kumaiti’. The latter are considered green aroma cultivars. These three types of cultivars with different aroma characteristics can be significantly differentiated by using the principal component analysis (PCA) method. The contributions of volatiles to the apricot aroma were assessed by using the partial least squares regression (PLSR) model. Esters, terpenes, and C6 components were shown to be responsible for the fruity, floral, and green character of fresh apricots, respectively.

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To study the effects of soil nitrogen (N) fertilization on tea growth, quality and yield, a controlled experiment with green tea [Camellia sinensis (L.) O. Ktze] was conducted. Five N fertilization treatments in soil were designed: 0, 0.97, 1.94, 3.88, and 5.82 g/kg/pot, which were subsequently recorded as N0, N1, N2, N3, and N4. The changes to young shoot biomass, total N and carbon (C), Soil and Plant Analyzer Development (SPAD) value, photosynthetic parameters, senescent characteristics, endogenous hormones, and the quality of green tea leaves were investigated. The results showed that with the increase in N fertilization level, the young shoot biomass, total N and C, SPAD value, net photosynthetic rate (P N), transpiration rate (T r), stomatal conductance (g S), superoxide dismutase activity, indoleacetic acid, gibberellin, zeatin (ZT), caffeine, and amino acids increased at first and then decreased, the maximums appeared at 3.88 g/kg/pot; whereas the intercellular CO2 concentration (C i), malondialdehvde contents, abscisic acid (ABA), polyphenol contents, and the ratio of polyphenols (PP) to free amino acid decreased at first and then increased, the minimums appeared at 3.88 g/kg/pot. The immediately significant change in all parameters appeared after 1 month of N treatments. The experiment showed that 3.88 g/kg/pot N fertilization level was the best for growth, quality, and yield of tea, which could provide a theoretical basis for short-term N fertilization management in tea tree.

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Efficient nitrogen (N) fertilizer management is crucial for ensuring the maximum economic yield and reducing the risk of environmental pollution. The objective of this study was to determine the effect of N fertilizer management on root yield and N uptake of radish in southern China by using 15N isotope tracing. A 2-year field experiment was conducted with three N rates (0, 60, and 120 kg N/ha) and two different application proportions, viz, A [50% at basal, 20% at 15 days after seeding (DAS), 30% at 30 DAS] and B (30% at basal, 20% at 15 DAS, 50% at 30 DAS) for each N rate, which were expressed as N0, N60A, N60B, N120A, and N120B, respectively. The results showed that root yields were significantly increased with N rates increasing from 0 to 120 kg N/ha. The root yields for N120A and N120B were 67.60 t·ha−1 and 72.50 t·ha−1 at harvest, 64.07% and 66.67% higher than those for the treatments of N60A and N60B, respectively. Mean radish recovery of N fertilizer ranged from 25.90% at N120A to 32.60% at N60B, and N fertilizer residual rate in the soil ranged from 11.50% at N120A to 14.90% at N60B. About 17.50% to 35.70% of total uptake of 15N derived from basal fertilizer was absorbed at seeding stage. However, 61.87% to 80.18% of total uptake of 15N derived from topdressing fertilizer absorbed at root expanding stage. Therefore, appropriate nitrogen application with increasing topdressing nitrogen amount could increase root yield of radish and the nitrogen recovery efficiency. Nitrogen fertilizer application recommended was 120 kg N/ha with 30% for basal, 20% for 15 DAS and 50% for 30 DAS in this study.

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Three kinds of expression vectors of a pollen-S determinant were constructed to provide a reference for molecular breeding of self-compatible (SC) Prunus species. An S-haplotype-specific F-box (SFB) protein gene from the ‘Xiaobaixing’ apricot (Prunus armeniaca) was cloned by reverse transcription polymerase chain reaction (RT-PCR) and 3′-rapid-amplification of cDNA ends (3′-RACE). A 1136-bp sequence complementary to the 3′-end of the cDNA (GenBank accession number KP938528.2) with a 912-bp complete open reading frame (ORF) was obtained. The deduced amino acid sequence contained an F-box domain, two variable regions, and two hypervariable regions with structural characteristics similar to SFB in other Rosaceae plants. Sense, antisense, and RNA interference (RNAi) vectors for SFB were constructed by enzyme restriction. The target fragment was restricted using the corresponding restriction enzyme and then directionally inserted between the 35S cauliflower mosaic virus promoter and the nopaline synthase terminator (NOS-ter) of the expression vector pCAMBIA-35S-MCS-NOS-NPTII. The intron-containing hairpin RNA (ihpRNA) was obtained by fusion PCR. The constructed vectors were transferred into Agrobacterium tumefaciens strain LBA4404 by freezing/thawing. The RNAi vector of SFB was also transformed in tobacco (Nicotiana tabacum). The successful construction of these three expression vectors provides a basis for transforming ‘Xiaobaixing’ apricot and the breeding of SC Prunus cultivars.

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Ferric chelate reductase (FRO) is a critical enzyme for iron absorption in strategy I plants, reducing Fe3+ to Fe2+. To identify FRO family genes in the local Citrus junos cultivar Ziyang Xiangcheng and to reveal their expression model, the citrus (Citrus sp.) genome was searched for homologies of the published sequence CjFRO1. Five FROs were found, including CjFRO1; these were named CjFRO2, CjFRO3, CjFRO4, and CjFRO5, respectively, and cloned via reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) PCR. The deduced amino acid sequences of five CjFROs contained flavin adenine dinucleotide (FAD)-binding motifs, nicotinamide adenine dinucleotide (NAD)-binding motifs, and 6–10 transmembrane domains, with isoelectric points between 6.73 and 9.46, and molecular weights between 67.2 and 79.9 kD. CjFRO1 and CjFRO2 were predominantly found in the aboveground parts of C. junos, with CjFRO1 highly expressed in leaves, and CjFRO2 largely expressed in stems and leaves. CjFRO3 was less expressed in roots, stems, and leaves. CjFRO4 and CjFRO5 were predominately found in roots. Under iron-deficient conditions, CjFRO4 was significantly and specifically increased in the roots of C. junos, whereas CjFRO1 was upregulated in the roots and leaves.

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Head splitting resistance (HSR) in cabbage is an important trait closely related to appearance, yield, storability, and mechanical harvestability. In this study, a doubled haploid (DH) population derived from a cross between head splitting-susceptible inbred cabbage line 79-156 and resistant line 96-100 was used to analyze inheritance and detect quantitative trait loci (QTLs) for HSR during 2011–12 in Beijing, China. The analysis was performed using a mixed major gene/polygene inheritance method and QTL mapping. This approach, which uncovered no cytoplasmic effect, indicated that HSR can be attributed to additive-epistatic effects of three major gene pairs combined with those of polygenes. Major gene and polygene heritabilities were estimated to be 88.03% to 88.22% and 5.65% to 7.60%, respectively. Using the DH population, a genetic map was constructed with simple sequence repeat (SSR) markers anchored on nine linkage groups spanning 906.62 cM. Eight QTLs for HSR were located on chromosomes C4, C5, C7, and C9 based on 2 years of phenotypic data using both multiple-QTL mapping and inclusive composite interval mapping. The identified QTLs collectively explained 37.6% to 46.7% of phenotypic variation. Three or four major QTLs (Hsr 4.2, 7.2, 9.3, and/or 9.1) showing a relatively larger effect were robustly detected in different years or with different mapping methods. The HSR trait was shown to have a complex genetic basis. Results from QTL mapping and classical genetic analysis were consistent. Our results provide a foundation for further research on HSR genetic regulation and molecular marker-assisted selection (MAS) for HSR in cabbage.

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Hydrogen sulfide (H2S) has been proven to be a multifunctional signaling molecule in plants. In this study, we attempted to explore the effects of H2S on the climacteric fruit tomato during postharvest storage. H2S fumigation for 1 d was found to delay the peel color transition from green to red and decreased fruit firmness induced by ethylene. Further investigation showed that H2S fumigation downregulated the activities and gene expressions of cell wall–degrading enzymes pectin lyase (PL), polygalacturonase (PG), and cellulase. Furthermore, H2S fumigation downregulated the expression of ethylene biosynthesis genes SlACS2 and SlACS3. Ethylene treatment for 1 d was found to induce the expression of SlACO1, SlACO3, and SlACO4 genes, whereas the increase was significantly inhibited by H2S combined with ethylene. Furthermore, H2S decreased the transcript accumulation of ethylene receptor genes SlETR5 and SlETR6 and ethylene transcription factors SlCRF2 and SlERF2. The correlation analysis suggested that the fruit firmness was negatively correlated with ethylene biosynthesis and signaling pathway. The current study showed that exogenous H2S could inhibit the synthesis of endogenous ethylene and regulate ethylene signal transduction, thereby delaying fruit softening and the ripening process of tomato fruit during postharvest storage.

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