In angiosperms, seed development initiates from double fertilization, which produces a diploid embryo and a triploid endosperm. The endosperm, a terminally differentiated tissue that nourishes the embryo during seed development and germination, is the prominent tissue of imprinting in plants. Proper endosperm development is crucial for normal embryo and seed development. The expression of imprinted genes is regulated by epigenetic mechanisms, including DNA methylation, H3K27 trimethylation and PolIV-dependent siRNA (p4-siRNA). Such epigenetic regulation of imprinting is vital to proper endosperm development and seed viability. Recent studies show that endosperm DNA methylation is reduced genome-wide, which likely originates from demethylation in the central cell nucleus of the female gametophyte. This review focuses on the latest research advances in the epigenetic regulation in plant seed development, including the mechanism of plant genomic imprinting and dynamics of the genome-wide demethylation in endosperm.

Cold-regulated proteins (CORPs) are induced by cold and thus closely related with cold tolerance. Most cold-induced genes may respond to water stress. We used RT-PCR to confirm that cold-induced siCOR in Sasussured involucrata was also induced by water stress. To investigate the possible role of S. involucrata siCOR in drought tolerance, we performed the drought-tolerance analysis using siCOR transgenic tobacco. Compared with untransformed wild-type (WT) plants, transgenic lines had greener leaves and more roots. Water stress experiments showed transgenic lines with delayed and slightly wilted leaves, but they recovered faster and more completely after rewatering as compared with WT plants. Transgenic lines also showed lower reduction of relative water content and relative quantum yield of PSII and smaller increase of relative conductivity and malondialdehyde content as compared with WT plants. Under drought stress simulated with PEG6000 treatment, transgenic T3 seeds showed higher germination rate and reduced inhibition of main root growth than WT. These results suggested that siCOR may play an important role in drought stress.

N₂O and CH₄ are two important greenhouse gases. However, their sources have not been well characterized. Plants are known to emit N₂O and CH₄, which has received widespread attention. We investigated N₂O and CH₄ emissions from fresh aboveground parts (branches and leaves) of 8 xerophytic herbaceous plants. All species could emit both N₂O and CH₄. Lolium perenne, Ixeridium sonchifolium and Spinacia oleracea showed high CH₄ emission, with fluxes of 165.38, 52.28 and 21.64 ngCH₄·g^–1dw·h^–1, respectively. I. sonchifolium, Artemisia mongolica, Glycine max and S. oleracea emitted more N₂O, with fluxes of 7.19, 6.92, 5.44 and 4.05 ngN₂O·g^–1dw·h^–1, respectively. These results provide further evidence of the universality of plants emitting N₂O and CH₄ but also reveal suitable plant species (I. sonchifolium and S. oleracea) for further mechanistic studies.

We collected 144 dinoflagellate cyst samples at 24 stations in the Bohai Sea in May and August 2008 to investigate species diversity and geographical distribution, as well as water eutrophication. We identified 32 dinoflagellate cyst species belonging to 6 groups, including 11 species of Protoperidinioids, 6 Gymnodinioids, 7 Gonyaulacoids, 5 Calcoidinellids, 2 Diplopsalids and 1 Tuberculodinioid. In the 17 autotrophic dinoflagellate cyst species, the dominant species are Scrippsiella trochoidea, and Polykrikos schwartzii and Protoperidinium conicum in the 15 heterotrophic dinoflagellate cyst species. Alexandrium tamarense, a species producing paralytic shellfish poisoning toxins, was found only at 3 stations. In general, the enriched heterotrophic dinoflagellate cyst species indicates relatively high eutrophication in the Bohai Sea. The predominance of S. trochoidea contributed substantially to the formation of harmful algal blooms in the studied area. We collected 10 cm vertical surface sediments from each sampling site and cut them into 3-cm-high sections representing the surface, middle and bottom layers. Species compositions were similar among the 3 layers and ranged from 5.58 to 7.29 in species numbers and from 58.82 to 103.57 cysts·g^–1 dry weight in density. The mean biodiversity indexes in May in the surface, middle and bottom sediments were 1.69, 1.61 and 1.52 and in August 1.83, 1.89, and 1.60.

We studied the morpho-anatomic characteristics of the clonal growth of root suckers of Populus pruinosa by the conventional paraffin method. Transverse lateral roots were formed by periderm, secondary vascular tissue, and the tetrarch’s primary xylem, with developed vascular rays and secondary elongated parenchyma in secondary vascular tissues. The clonal growth of root suckers of P. pruinosa is based on the development and growth of adventitious buds on transverse lateral roots. Adventitious buds originated from cork cambium of transverse lateral roots and expressed the time characteristics of synchronous and asynchronous generation and the spatial characteristics of single-point and multi-point gathered generation. The cork cambium cells formed primordia of adventitious buds by cell division. The cell division, proliferation, and differentiation of adventitious primordia formed visible primordia on the surface of transverse lateral roots and directly developed as root suckers. The features of adventitious bud development, distribution, and growth were the key reason for root suckers to keep growing to different sizes and form a densely fasciculate shape. P. pruinosa has good ability for clonal growth of root suckers.

Although the proteasome pathway has long been considered one of the most important proteolytic systems in pollen development, the dynamic changes of proteasome activity and distribution during pollen development are largely unknown. We performed fluorogenic kinetic assays using fluorogenic substrate sLLVY-AMC to measure proteasome activity in Pinus bungeana pollen grains. Our experiment results revealed that proteasome activity increased from the uninucleate to 3-cell stage, but slightly decreased in mature pollen grains. Immunofluorescence labelling detected proteasome signals in the nuclei of pollen grains at all stages as well as in cytosol. Unequal distribution of proteasomes was observed in the two degradating prothallial cells. Our data indicate a link between pollen development and dynamic changes in activity and distribution of proteasome, and proteasome might take a part in the degradation of prothallial cells.

We established the metabolomics method for investigating metabolites in Corydalis yanhusuo bulbs by gas chromatography-mass spectrometry. We also investigated the effect of different volumes of extracts and derived reagents (MSTFA) for peak signal intensity and numbers. We determined the best conditions with each 100 mg material extracted by use of 300 μL extract and 100 μL MSTFA. To detect samples of C. yanhusuo tuber, we obtained 92 kinds of compounds, which contained 5 fatty acids, 21 organic acids, 16 amino acids, 6 sugars, 23 other ingredients, and 21 unknown compounds. We also studied the pattern recognition of C. yanhusuo tuber metabolites by principal component analysis. We could provide valid data and reference values for further research into C. yanhusuo tubers.

The technique of pollen-mediated plant genetic transformation assisted by ultrasonication was patented by the Biotechnology Research Center of the Shanxi Academy of Agricultural Sciences. Here, we further investigated the conditions for sampling, storage and treatment of maize (Zea mays L.) pollen and effects on in vitro germination of pollen with the method. The optimal sucrose concentration for pollen suspension solution differed for maize pollen collected from plants with different flowering time. We determined the storage time and condition of pollen and their effects on pollen germination after ultrasonication. These results would be useful for improving pollen vitality in genetic transformation and verifying the feasibility of this plant transformation technique. We discuss some key steps for conducting in vitro germination of maize pollen and related parameters to increase transformation efficiency of pollen-mediated plant genetic transformation.

We examined the effect of genotypes, explant types, combinations and concentrations of growth regulators on sesame callus induction and shoot regeneration with the cultivars Sesamum indicum L., 2n=26; the wild species S. radiatum, 2n=64, and S. schinzianum, 2n=64; and their distant hybrid strain S. schinzianum × S. indicum. We established the technical system of sesame callus induction and shoot regeneration with high frequency. Among the growth regulators, BA and NAA are suitable for inducing compact green callus, which gives a high differentiation frequency. The optimal medium for sesame callus induction and differentiation was MS basal medium supplemented with 0.1 mg·L^–1 NAA, 2.0 mg·L^–1 6-BA and 30 g·L^–1 sucrose. With this medium, the ratios of the highest level of callus induction and differentiation were 97.50% and 94.02% respectively, which were obtained from wild sesame hypocotyl explants, with the corresponding frequencies of 40.60% and 8.16% for cultivar hypocotyl explants. For the immature embryo explants from the distant hybrids, we achieved the maximum ratios of callus induction (46.67%) and differentiation (89.29%) with this medium. These results form the basis for both germplasm conservation and transgene studies in sesame.

Sorghum bicolor is one of the most important crops in the world, used for food, fodder, alcoholic beverages, as well as biofuel production, and also serves as a C₄ model plant. Aphids are major agricultural pests injuring nearly all cultivated crops. Sorghum aphid (Melanaphis sacchari), greenbug (Schizaphis graminum) and corn leaf aphid (Rhopalosiphum maidis) are the major aphid species damaging sorghum growth. We lack sorghum aphid-resistance germplasm and systematic study. Some progress has been made in sorghum greenbug resistance research. Recently 20 resistant quantitative trait loci (QTL) were mapped, and the maximum resistant phenotypic variation explained by a single QTL reached 80.3%, but little is known about the resistance to sorghum aphid and corn leaf aphid. The morphological characters and chemical contents of sorghum could affect aphid resistance. Such resistance-related traits may be useful for breeding. The published sorghum and pea aphid (Acyrthosiphon pisum) genome sequences could help in better understanding the aphid-plant interaction and plant aphid-resistance mechanism. Two aphid-resistance genes have been cloned, but more genes and QTLs are needed. Here, we review recent studies of sorghum aphid resistance and propose possible future research.

The suspensor is a terminal embryonic structure that provides nutrients and growth regulators to the embryo proper during embryo development. In contrast to the embryo proper, the suspensor has a simple structure and a one-cell type that has a unique advantage in studies of gene regulation and cell fate determination. This paper presents advances in studies of suspensor formation, characteristics of the suspensor cell, genes that may be involved in suspensor development, and possible roles that suspensors play during embryogenesis.