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2019  Vol. 37  No. 2

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Ecology and Biogeography
Abstract:
Sphagnum species are among the most important carbon sequestration plants in peatland systems and are closely related to regional and global material energy balance. Here, we analyzed the spectral characteristics of the Sphagnum magellanicum Brid community based on the measured canopy spectrum and remote sensing sensor simulated spectrum. Results showed that the spectral differences between S. magellanicum and northern coniferous forest were obvious, and the best spectral recognition intervals were 740-1140 nm and 1230-1412 nm. In the visible light band, the ‘green peak’ position of S. magellanicum was different from that of Picea engelmannii Parry ex Engelmann and Pinus contorta Douglas ex Loudon. Spectral identification characteristics of Phyllostachys heteroclada Oliver and S. magellanicum were concentrated in the visible-near-infrared bands at 400-550, 560-696, and 1025-1143 nm. There were subtle differences in the characteristic spectral bands between S. magellanicum, northern coniferous forest, and P. heteroclada; for example, S. magellanicum and P. heteroclada showed good separability in the visible light region, thus the characteristic spectral width of the S. magellanicum community in different latitudes was different. The infrared band was the best spectral range for S. magellanicum recognition. The recognition effect of S. magellanicum was better at the multispectral remote sensing level, whereas the recognition performance of the sensor was as follows:MSI > ALI > OLI > ASTER. In the spectral characteristic analysis of the two S. magellanicum communities, the spectral dimension reduction ability of the derivative, logarithm, and continuum removal methods was different, among which the continuum removal method was the best.
Abstract:
Based on 123 distribution points of Astragalus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao and 19 ecological variables, four ecological niche models (i.e., BIOCLIM, DOMAIN, GARP, and MAXENT) were used to predict the potential distribution areas of Astragalus membranaceus, with the different models then judged and compared using areas under the receiver operating characteristic curves (AUC) and Kappa values. Results showed that the four models had good prediction accuracy and consistency, with AUC values above 0.8 and Kappa values above 0.6. The DOMAIN model demonstrated the highest AUC and Kappa values, indicating that the prediction accuracy and results of this model were optimal and stable. The predicted suitable area range of the GARP model was the widest, with the MAXENT and BIOCLIM models showing similar prediction ranges and DOMAIN demonstrating relatively dispersed prediction regions. The four models showed that the northwest regions could be used as major production areas for A. membranaceus var. mongholicus cultivation. The prediction results indicated that the potential distribution areas for A. membranaceus var. mongholicus were mainly located in north of 33°N, and included Mongolia, Shaanxi, Shanxi, Gansu, Ningxia, Hebei, and the border area of northeastern provinces and Inner Mongolia. In addition, small potentially suitable areas were also located in Xinjiang, Tibet, Qinghai, and Sichuan. However, the most suitable areas were distributed in Gansu, Ningxia, Shaanxi, Shanxi, Hebei and Inner Mongolia Autonomous Region.
Abstract:
To reveal the dynamic changes in ecosystem patterns, we analyzed ecosystem composition structure and variation using distribution data collected in 2010 and 2015 for priority areas in Hubei Province. Results showed that:(1) there were seven types of ecosystems, including forest, shrub, grassland, wetland, cropland, urban land, and bare land, with the forest area being the largest, followed by shrub and farmland. Vegetation coverage was relatively high, and the overall ecological environment was relatively good; (2) All ecosystem types changed over the five years; forest, shrub, and bare land areas all decreased, whereas grassland, wetland, cropland, and urban areas all increased, with the urban area changing significantly; (3) Urbanization, water resource development, ecological protection and restoration, agricultural development, geological disasters, and climate change all significantly impacted the ecosystems, with urbanization found to be the major factor. To protect the sustainable development of the ecosystems within the priority areas, ecological protection red lines should be delineated and combined with various protected areas, land use should be reasonably planned in the course of urbanization, arable land should be protected, and the development of important wetlands should be prohibited or restricted.
Abstract:
Based on a systematic survey of rare and endangered plants in Gutianshan National Nature Reserve, Qianjiangyuan National Park, we conducted a systematic study on the species composition, conservation value, geographic characteristics, and distribution of rare and endangered plants in the region. Results showed a total of 63 national and provincial endangered seed plant species in the Gutianshan area, belonging to 32 families and 55 genera. Among them, one Class Ⅰ and 15 Class Ⅱ species were included in the National List of Key Protected Wild Plant, along with 15 species in the China Plant Red Data Book, 19 species in Zhejiang Province's Key Protected Wild Plants, and the remaining species in the China Species Red List and Threatened Species List of China's Higher Plants. The majority of threatened species maintained only small populations and a narrow distribution range, except for a few species including Glycine soja, Michelia skinneriana, and Cleyera japonica. Threatened species such as Ulmus elongata, Emmenopterys henryi, Torreya grandis, Euchresta japonica, and Croomia japonica only sporadically spread into the core area of the reserve, whereas species such as Taxus wallichiana var. mairei and Ormosia henryi were scattered in the buffer or test zones. Floristic geographic analysis showed that a higher percentage of threatened species were temperate rather than tropical genera and the degree of endangerment for endemic genera was high. Improved measures should be established to strengthen the protection of these rare and endangered species.
Abstract:
To explore the paternal origin of offspring and the pollen dispersal pattern in natural populations under open-pollination, we conducted paternity analysis for seeds of H. rhamnoides ssp. sinensis using SSR markers. Results showed that in 104 seedlings of 193 open-pollinated offspring, the pollen source was identified at an 80% confidence level. In 20 male parents deduced, 16 were H. rhamnoides ssp. sinensis and four were H. neurocarpa S. W. Liu et T. N. He. Pollination pattern analysis showed that the effective distance of H. rhamnoides ssp. sinensis pollen dispersal was in the range of 3-71 m, with an average distance of 20.4 m. Furthermore, 87.23% and 78.95% of the effective pollen received by the two respective female parents examined came from a distance range of 30 m. These results indicate that the natural populations of H. rhamnoides ssp. sinensis are mainly pollinated within a close range. In addition, in the seabuckthorn hybrid zone of the upper reaches of Heihe River, the average pollen contribution from H. neurocarpa to the offspring of H. rhamnoides ssp. sinensis reaches 14.84%, indicating that H. rhamnoides ssp. sinensis and H. neurocarpa possess a relatively high frequency of contemporary interspecific pollen flow.
Genetics and Breeding
Abstract:
‘Jinyuan’ is a kiwifruit cultivar bred in 2002 by backcrossing interspecific hybrid cultivar ‘Jinyan’ (A. chinensis×A. eriantha) as the female parent and Chinese kiwifruit (A. chinensis) as the male parent, which produced the medium-mature yellow fruit from the F1 group. The botanical characters, specificity, nutrient composition, and storage ability of the ‘Jinyuan’ kiwifruit were studied in this paper. Results showed that the ‘Jinyuan’ fruit had a short columnar shape, with a weight of 80-100 g. The flesh of the soft ripening fruit was orange-yellow, and the number of petals and filaments were close to those of its female parent ‘Jinyan’. The corolla diameter and number of stigmas were 9.31% and 52% higher than that of ‘Jinyan’, respectively. The length of the flower stalk was 16.75% lower, and the germination and fruit branching rates were also slightly lower than that of ‘Jinyan’ but were 55.26% and 43.33% higher than the ‘Hayward’ variety, respectively. The contents of soluble solids, total sugar, and organic acids in ‘Jinyuan’ were similar to those of ‘Jinyan’, but vitamin C content was 4.63% higher than ‘Jinyan’ and 2.2 times higher than ‘Hayward’. ‘Jinyuan’ exhibited mineral element richness, with P and K content 30.86% and 22.53% higher than that of ‘Jinyan’, respectively, and with Mg content 24.86% higher than that of ‘Hayward’. ‘Jinyuan’ also demonstrated abundant amino acid content (8 mg/g), and the E/N and E/T values were higher than those of ‘Jinyan’ and ‘Hayward’, close to the ideal model. After 150 d of storage in a harsh environment (T:1℃ -2℃, RH:90%-95%), the good fruit rate was above 80%. After 200 d of storage, the good fruit rate was still 65%. The ‘Jinyuan’ storage property was slightly lower than that of ‘Jinyan’, but significantly higher than that of ‘Hayward’. Three bands were observed after amplification by Geo7-223, which were different from those of ‘Jinyan’ and ‘Jintao’ at the molecular level, thus exhibiting specificity. Therefore, the ‘Jinyuan’ kiwifruit possessed good agronomic characteristics and quality, which provides a choice for improving yellow-fleshed kiwifruit and responding to market demand.
Abstract:
Cyanobacteriochromes contain GAF (cGMP phosphodiesterase, adenylyl cyclase, and FhlA protein) domains in the N-terminal region that bind phycocyanobilin autocatalytically. In the current study, we amplified the cyanobacteriochrome gene fragment of all1280 gaf2 from Anabaena sp. PCC 7120 using PCR, and then inserted it into pET-30a(+). For over-expression, both pET-all1280 gaf2 and pACYC-ho1-pcyA, which catalyze phycocyanobilin (PCB) biosynthesis, were transformed into E. coli BL21 (DE3). Cells harboring pET-all1280 gaf2 and pACYC-ho1-pcyA expressed chromophorylated All1280 GAF2 successfully. Results showed that All1280 GAF2 underwent reversible photoconversion between the 15E form (λmax=560 nm) and 15Z form (λmax=413 nm). Using fluorescent microscopy, we detected a red fluorescence/no fluorescence reversible photoconversion of All1280 GAF2 in E.coli BL21(DE3). Cys53 was essential for photoconversion of All1280 GAF2 because its mutagenesis resulted in a PCB adduct, which exhibited no photoconversion but stable red fluorescence. Compared with the wild-type, All1280 GAF2(C53A) had stronger red fluorescence with higher extinction coefficients and fluorescence yields. It is expected that these two constructs could serve well in the labeling of living cells.
Abstract:
The mitochondrial genome of Oryza rufipogon Griff. was used to analyze the codon usage characteristics of protein-coding genes and the differences with Asian cultivated rice (O.sativa L.), and to explore the influencing factors of codon usage bias and codon evolution. Results showed that the effective number of codons (Nc) ranged from 45.32 to 61.00, indicating that codon bias was weak. GC content at the three codon positions was 49.18%, 42.67%, and 40.86%. The Nc value was significantly correlated with GC3 but not with GC1 or GC2, suggesting that base composition at the third codon position had a greater effect on codon bias. In the corresponding analysis, the first axis showed 9.91% variation and was significantly correlated with GC3s, Nc, CBI, and Fop. Furthermore, GC12 showed non-significant correlation with GC3. Codon bias in the mitogenome of O. rufipogon was mainly affected by natural selection. In addition, we identified 21 optimal codons, with most of the preferred synonymous codons ending in A or T. The mitochondrial codons showed convergent evolution with Oryza chloroplast codons, but different preferences with the nuclear genome. Based on neutrality plot analysis, PR2-plot analysis, and RSCU analysis, we found no significant differences among the three Oryza species. Our results also confirmed homogeneity in mitochondrial codon usage among the three Oryza species.
Abstract:
High-throughput sequencing was used to analyze the gene expression of the reproductive buds, fruits, and shoots of Hylocereus undulatus Britt ‘Dahong2’ at different developmental stages. In total, 468.68 Gb of raw data were generated and de novo assembled into 239 152 transcripts and 162 519 unigenes. Approximately 53.74% of all unigenes were annotated based on seven public databases. In total, 600 283 SNPs and 56147 SSRs were identified from 43 506 and 16 251 unigenes, respectively. Gene expression analysis showed that 31, 7, 5, 152, 17, 63, 17, and 8 unigenes were specifically expressed in Fl510, Fl513, Fl514, Fl518, F711, F715, S513, and S419, respectively. Through GO and KEGG enrichment analyses, several unique GO terms and metabolic pathways in different tissues were identified; for example, terpenoid backbone biosynthesis (ko00900) showed significant enrichment in Fl510. We also focused on the molecular mechanism of H.undulatus ‘Dahong2’ flower development and identified a suite of unigenes involved in floral development, including COL, FT-like, meristem identity, and organ identity genes.
Abstract:
The genetic loci of the SRAP molecular marker in 780 Pinus yunnanensis Franch samples from the whole distribution area were used to establish a high-quality P. yunnanensis timber germplasm bank. Four P. yunnanensis germplasm subsets were constructed by improved least distance stepwise sampling at four sampling proportions, i.e., 10%, 20%, 30%, and 40%. Results showed that polymorphic locus retention rate of the four germplasm subsets was above 90% and the allele retention rate was greater than 95%. The minimum values of the five genetic diversity parameters were obtained from the germplasm subset constructed using the 10% sampling proportion, and the genetic diversity in the population of this subset was smaller than that of the original germplasm. Mean t-tests between the original and germplasm subsets showed significant differences between the 10% sampling ratio germplasm subset and the original. Furthermore, for the variance t-tests, several indicators of genetic diversity demonstrated significant differences between the original germplasm and the 10% and 20% germplasm subsets, respectively, and the variances of these germplasm subsets were smaller than those of the original. The correlation coefficients of the mean genetic diversity between the original germplasm and the four germplasm subsets all reached 0.99. The correlation coefficients of genetic diversity between the original and the 40% and 30% germplasm subsets were more than 0.80. The average genetic distance of the 30% germplasm subset was 52.16% higher than that of the original germplasm; at the same time, the distribution pattern of variance components of the original germplasm was well maintained and similar clustering to the original germplasm was achieved with a large genetic distance. Therefore, the 30% sampling proportion germplasm subset could be used as a representative subset of the germplasm resources of P. yunnanensis.
Abstract:
Phenylalanine ammonia-lyase (PAL) is the first key enzyme in the synthesis of flavonoids and the rate-limiting enzyme of the phenylpropanoid pathway, which is associated with secondary metabolites, growth and development, as well as defense of plants. In this study, the mRNA of Arisaema heterophyllum Blume was used as a template and the full-length open reading frame (ORF) of the phenylalanine ammonia-lyase gene (AhPAL) was amplified by real-time polymerase chain reaction (RT-PCR). The structure and physicochemical properties of AhPAL were then analyzed by bioinformatics. Results showed that the ORF of AhPAL was 2,184 bp in length, encoding a protein with 727 amino acids. Furthermore, AhPAL had the closest relationship with PAL of Tulipa fosteriana W. Irving, with a sequence identity of 88%. Structure analysis indicated that AhPAL was a homotypic tetramer, and each monomer consisted of three domains. Among these domains, the MIO domain was highly important for the activity of AhPAL, containing a conserved sequence of the PAL family and Ala-Ser-Gly triad residues. The expression levels of three AhPAL unigenes in the roots, tubers, and leaves were detected by quantitative RT-PCR (qRT-PCR), with higher expression found for all three in the roots compared with that in the leaves and tubers.
Physiology and Development
Abstract:
Aquatic plants are important primary producers in the littoral zone of lakes and wetlands. As aquatic plants have a close relationship with the aquatic environment, their leaves usually do not need to adapt to water shortages in the soil. Therefore, the leaf traits of aquatic plants are likely to be different from those of terrestrial plants. In addition, leaf vein type is the fundamental basis of leaf functional traits; however, previous studies on leaf vein types and functional traits have not yet been conducted for aquatic plants. In this study, nine aquatic plants with different vein type were selected to analyze the relationship between the changes in leaf traits (e.g., morphology, pigment content, and chlorophyll fluorescence) and vein type after vein cutting. Results showed that the three species with parallel veins exhibited strong tolerance to the main vein cut, whereas the four species with pinnate veins demonstrated significantly reduced pigment content and inhibited leaf growth following the main vein cut. In contrast, the side vein cuts had distinct effects on different species, indicating species-specific effects. Based on leaf vein type, this study provides theoretical guidance for species selection in the re-establishment of aquatic plants in the littoral zone of large lakes.
Abstract:
Based on the model plant Arabidopsis thaliana (L.) Heynh, we studied the biological effects of carbon quantum dots (CQDs), a new nanomaterial, and investigated their distribution and transportation, effects on growth and development, photosynthetic pigment content, oxidative stress, and stress-related gene expression levels in A. thaliana. Results showed that CQDs could be absorbed by the roots of A. thaliana and transported continuously to the leaves, which had no significant effect on seed germination rate, but significantly promoted the growth of seedling roots and plant weight. With the increase in CQD concentration, the pigment content in the chloroplast of seedlings decreased significantly, whereas the content of proline and malondialdehyde increased at first and then decreased. Superoxide dismutase (SOD) and catalase (CAT) played a leading role in the antioxidant enzyme system, and showed increasing and then decreasing activity as CQD concentration increased. The accumulation of endogenous hydrogen peroxide (H2O2) in leaves also indicated that CQDs could induce oxidative stress with concentration-dependent effects. Sulfur assimilation and stress-related genes were down-regulated after CQD treatment, which might be related to the characteristics of the CQD particles themselves. These results are of great significance for exploration of the molecular mechanisms of the bio-effects of nanomaterials on plants and for evaluating their biosafety.
Abstract:
Dalbergia odorifera T. Chen was used to study the effects of different concentrations of exogenous Ca2+ on seedling growth and physiological characteristics under different artificial temperature conditions. Significant effects were found on stem height, leaf length, Pn, Gs, Tr, and photosynthetic pigment content under different concentrations of Ca2+ at normal temperature. However, limited effects were found on the relative water content and dew point water potential of leaves, relative conductivity, MDA, and soluble protein content. The optimum Ca2+ concentration to improve plant growth was 5 mmol/L. In addition, stem height, leaf length, Pn, Gs, Tr, WUE, content of photosynthetic pigment, relative water content, dew point water potential, relative conductivity, MDA, and soluble protein content were significantly affected by cold stress. These negative effects could be alleviated by applying exogenous Ca2+, with the optimal Ca2+ concentration again found to be 5 mmol/L, followed by 10, 15, and 2.5 mmol/L under normal temperature and cold stress. The results of this study provide scientific guidance in regard to the adaptation of D. odorifera to cold stress and its cultivation in low temperature regions of subtropical areas.
Review
Abstract:
Polyploidy(or whole-genome doubling) is an important pathway for plant speciation, with existing angiosperms possibly occurring once or even multiple times. The traditional definition of polyploidization is that the number of chromosomes doubles relative to the ancestral group. The most commonly used research method for understanding polyploidy is karyotype analysis, which provides basic cytological parameters of the studied species, including chromosome number, ploidy level, karyotypic asymmetry, and karyotype coefficient of variation. At present, karyotype research has evolved from basic parameter analysis of species to multi-group/multi-disciplinary study, with an associated shift from lower taxonomic level (e.g., population, species, or family/genus) to higher taxonomic level research (e.g., tree of life). In addition, the integration of phylogeny and karyotypes will provide insightful evidence on the potential evolutionary characteristics and tendencies of karyotypes, and the cytological mechanism driving the evolution of plant diversity at the phylogenetic scale. Furthermore, exploring cytological features of the chromosome atlas or polyploidy at the regional or floral scale will help elucidate the influence of geo-ecological environmental shifts on chromosome ploidy. Additionally, constructing a regional chromosome atlas will shed light on the formation and evolutionary history of flora. Plant karyotype research provides new ideas for study on the origin and evolution of systematics, molecular phylogeny, tree of life, and floristic geography. As new methods are used in plant karyotype analysis and polyploidy, results on the effects and mechanisms will reveal the chromosomal evolution and cellular geographic features of plant groups and flora. Future trends in plant cytology research will be multi-disciplinary and integrate evidence from various research fields and will clarify the causes and significance of plant karyotype diversity at different levels to more fully understand plant species diversity and speciation.