MiR-674-5p Suppresses the Proliferation and Migration of Glioma Cells by Targeting Cul4b

Neurochemical Research - Glioma multiforme (GBM) is the most common malignant primary brain tumors. Despite the considerable advances in GBM treatment, it is still one of the most lethal forms of...     

Study on Antidepressant Effect and Mechanism of Crocin Mediated by the mTOR Signaling Pathway

Neurochemical Research - Crocin is a monomer of Chinese traditional herbs extracted from saffron, relieving depression-like behavior. However, its underlying mechanism of action remains unclear....     

Palynological evidence for the temporal stability of the plant community in the Yellow River Source Area over the last 7,400 years

Vegetation History and Archaeobotany - The terrestrial ecosystem in the Yellow River Source Area (YRSA) is sensitive to climate change and human impacts, although past vegetation change and the...     

高寒山区不同土地利用类型土壤养分化学计量特征及影响因素

了解高寒地区不同土地利用类型下土壤养分化学计量特征及其影响因素可为评估脆弱生态系统土壤质量和功能提供参数。通过测定青海省东部24个样点0—30 cm土壤基本理化性质(pH、容重BD、孔隙度P_s、黏粒含量C_y、土壤含水量SWC、有机碳SOC、全氮TN、全磷TP、速效氮AN和速效磷AP),并提取各样点环境因子数据(年均温MAT、年均降雨量MAP、年均蒸发量E_a、植被归一化指数NDVI、海拔ALT、坡度SG、地表粗糙度SR、经度LON和纬度LAT),分析了农、林、草三种土地利用类型下土壤养分化学计量比分布特征及其影响因素。结果表明,农地土壤有机碳SOC和全氮TN含量显著低于林地和草地(P<0.05),而全磷TP和速效磷AP含量则相反,农、林、草地速效氮AN含量无显著差异(P>0.05)。农、林、草地不同深度土壤C∶N(平均值19.93,变异系数<16%)和AN∶AP(平均值2.73,变异系数<71%)较为稳定且无显著差异(P>0.05),而农地C∶P和N∶P(平均值分别为19.27和0.99)却显...     

Enhanced Sucrose Loading Improves Rice Yield by Increasing Grain Size

Yield in cereals is a function of grain number and size. Sucrose (Suc), the main carbohydrate product of photosynthesis in higher plants, is transported long distances from source leaves to sink organs such as seeds and roots. Here, we report that transgenic rice plants (Oryza sativa) expressing the Arabidopsis (Arabidopsis thaliana) phloem-specific Suc transporter (AtSUC2), which loads Suc into the phloem under control of the phloem protein2 promoter (pPP2), showed an increase in grain yield of up to 16% relative to wild-type plants in field trials. Compared with wild-type plants, pPP2::AtSUC2 plants had larger spikelet hulls and larger and heavier grains. Grain filling was accelerated in the transgenic plants, and more photoassimilate was transported from the leaves to the grain. In addition, microarray analyses revealed that carbohydrate, amino acid, and lipid metabolism was enhanced in the leaves and grain of pPP2::AtSUC2 plants. Thus, enhancing Suc loading represents a promising strategy to improve rice yield to feed the global population.Rice (Oryza sativa) is a staple food for nearly one-half of the global population. Given the rapid growth of the world’s population, there is an urgent need to increase rice yield. Rice yield is a complex trait that is directly associated with grain size, panicle number, and the number of grains per panicle (Xing and Zhang, 2010). Increasing grain size is a prime breeding target, and several genes known to control rice grain size, such as GRAIN SIZE3 (GS3), GS5, GW2 QTL for rice grain width and weight (GW2), GW8, and rice seed width5, have been identified (Fan et al., 2006; Song et al., 2007; Shomura et al., 2008; Li et al., 2011a; Wang et al., 2012). However, our knowledge of the mechanisms that control rice yield is limited. Thus, further improving rice yield remains a challenge for breeders (Sakamoto and Matsuoka, 2008). Identifying and characterizing unique genes or targets that regulate yield traits would improve our understanding of the molecular mechanisms that regulate yield traits and facilitate the breeding of new rice varieties with higher yields.The carbohydrates in rice grains originate from photosynthesis that is carried out predominantly in leaves (sources). Therefore, grain filling and rice yield depend on the efficient transport of carbohydrates from the leaves to seeds (sinks). In most plants, Suc is the main carbohydrate transported long distance in the veins to support the growth and development of roots, flowers, fruits, and seeds (Baker et al., 2012; Braun, 2012). Recently, the entire pathway for the export of Suc from leaves has been elucidated (Baker et al., 2012; Braun, 2012). Suc is synthesized in leaf mesophyll cells and diffuses from cell to cell through plasmodesmata until it reaches the phloem parenchyma cells (Slewinski and Braun, 2010). The SWEET transporters mediate Suc efflux from the phloem parenchyma cells into the apoplast, where Suc is subsequently loaded into the phloem sieve element-companion cell (SE/CC) complexes by Suc transporters (SUTs; Braun and Slewinski, 2009; Ayre, 2011; Chen et al., 2012). The resultant accumulation of Suc in sieve elements produces a hydrostatic pressure gradient that results in the bulk flow of Suc through a conduit of contiguous sieve elements, leading to its arrival and unloading in sink tissues (Lalonde et al., 2004; Baker et al., 2012).Genetic evidence has demonstrated that apoplastic Suc phloem loading is critical for growth, development, and reproduction in Arabidopsis (Arabidopsis thaliana). AtSWEET11 and AtSWEET12 are localized to the plasma membrane of the phloem and are expressed in a subset of phloem parenchyma cells in minor veins. These transporters mediate Suc efflux from phloem parenchyma cells into the apoplast prior to Suc uptake by SE/CC (Chen et al., 2012). The atsweet11 or atsweet12 single mutants exhibit no aberrant phenotypes, possibly due to genetic redundancy. However, atsweet11;12 double mutants are mildly chlorotic and display slower growth and higher levels of starch and sugar accumulation in the leaves than do wild-type plants (Chen et al., 2012). Arabidopsis phloem-specific sucrose transporter (AtSUC2) is a phloem-specific SUT that is expressed specifically in companion cells (Stadler and Sauer, 1996). AtSUC2 plays an essential role in phloem Suc loading and is necessary for efficient Suc transport from source to sink tissues in Arabidopsis (Stadler and Sauer, 1996; Gottwald et al., 2000; Srivastava et al., 2008). The atsuc2 mutants show stunted growth, retarded development, and sterility. Furthermore, these mutants accumulate excess starch in the leaves and fail to transport sugar efficiently to the roots and inflorescences (Gottwald et al., 2000).The proper control of carbohydrate partitioning is fundamental to crop yield (Braun, 2012). It has been reported that increasing sink grain strength by improving assimilate uptake capacity could be a promising approach toward obtaining higher yield. For example, seed-specific overexpression of a potato (Solanum tuberosum) SUT increased Suc uptake and growth rates of developing pea (Pisum sativum) cotyledons (Rosche et al., 2002). In addition, the Suc uptake capacity of grains and storage protein biosynthesis was increased in transgenic wheat (Triticum aestivum) plants expressing the barley (Hordeum vulgare) SUT HvSUT1 under the control of an endosperm-specific promoter (Weichert et al., 2010). Moreover, it was recently found that these transgenic wheat plants had a higher thousand grain weight and grain width and length, as well as a 28% increase in grain yield (Saalbach et al., 2014).Since the carbohydrates in rice grains originate from photosynthesis in source leaves, and carbohydrate partitioning from source leaves to heterotrophic sinks (e.g. seeds) is mediated by Suc transport in plants (Lalonde et al., 2004; Ayre, 2011), enhancing the capacity for Suc transport from leaves to seeds theoretically could increase crop yield. However, until now, enhancing Suc transport from leaves to seeds has not been shown to improve yield (Ainsworth and Bush, 2011).Here, we tested the hypothesis that enhancing Suc transport from leaves to seeds would increase rice yield. We expressed Arabidopsis SUC2 under control of the phloem protein2 promoter (pPP2) in rice and found that enhancing Suc loading did indeed increase rice yield. The pPP2::AtSUC2 plants produced larger grain than the wild type and showed grain yield increases of up to 16% in field trials. Our results suggest that manipulating phloem Suc transport is a useful strategy for increasing grain yield in rice and other cereal crops.     

Novel Hypovirulence-Associated RNA Mycovirus in the Plant-Pathogenic Fungus Botrytis cinerea: Molecular and Biological Characterization

Botrytis cinerea is a pathogenic fungus causing gray mold on numerous economically important crops and ornamental plants. This study was conducted to characterize the biological and molecular features of a novel RNA mycovirus, Botrytis cinerea RNA virus 1 (BcRV1), in the hypovirulent strain BerBc-1 of B. cinerea. The genome of BcRV1 is 8,952 bp long with two putative overlapped open reading frames (ORFs), ORF1 and ORF2, coding for a hypothetical polypeptide (P1) and RNA-dependent RNA polymerase (RdRp), respectively. A −1 frameshifting region (designated the KNOT element) containing a shifty heptamer, a heptanucleotide spacer, and an H-type pseudoknot was predicted in the junction region of ORF1 and ORF2. The −1 frameshifting role of the KNOT element was experimentally confirmed through determination of the production of the fusion protein red fluorescent protein (RFP)-green fluorescent protein (GFP) by the plasmid containing the construct dsRed-KNOT-eGFP in Escherichia coli. BcRV1 belongs to a taxonomically unassigned double-stranded RNA (dsRNA) mycovirus group. It is closely related to grapevine-associated totivirus 2 and Sclerotinia sclerotiorum nonsegmented virus L. BcRV1 in strain BerBc-1 was found capable of being transmitted vertically through macroconidia and horizontally to other B. cinerea strains through hyphal contact. The presence of BcRV1 was found to be positively correlated with hypovirulence in B. cinerea, with the attenuation effects of BcRV1 on mycelial growth and pathogenicity being greatly affected by the accumulation level of BcRV1.