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Stem non-structural carbohydrates (NSCs) and its relationship with yield formation was investigated under low nitrogen (LN) and normal nitrogen (NN) treatments, using 46 recombinant inbred lines from Zhenshan 97 × Minghui 63 (Oryza sativa). Apparent contribution of transferred NSC to grain yield (AC(NSC) ) ranged from approximately 1 to 28% under LN and from 1 to 15% under NN. Concentration and total mass of NSC in stem (TM(NSC) ) at heading, apparent transferred mass of NSC (ATM(NSC) ) and AC(NSC) were larger under LN compared with NN. However, there was no significant difference in the apparent ratio of transferred NSC from stems to grain (AR(NSC) ). ATM(NSC) was positively correlated with grain yield, 1000-grain weight and AC(NSC) under both nitrogen levels, whereas AR(NSC) was highly correlated with harvest index and AC(NSC) . Leaf area contributed more strongly to grain yield compared with ATM(NSC) under both LN and NN. ATM(NSC) showed larger direct effects on grain yield under LN compared with NN. TM(NSC) at heading, small vascular bundles (SVBs) and spikelets per m(2) under LN had positive direct effects on ATM(NSC) . SVB and spikelets per m(2) under LN had larger and positive direct effects, and large vascular bundles had negative direct effects on AR(NSC) . TM(NSC) at heading and SVB under LN had positive direct effects on AC(NSC) . In brief, LN supply increased stem NSC accumulation and translocation to developing grain. Components of the source-sink-flow system showed different effects on NSC translocation and contribution to yield formation, depending on genotype and nitrogen level.

Type VI secretion systems (T6SSs) are involved in the pathogenicity of several Gram-negative bacteria. The VgrG protein, a core component and effector of T6SS, has been demonstrated to perform diverse functions. The N-terminal domain of VgrG protein is a homologue of tail fiber protein gp27 of phage T4, which performs a receptor binding function and determines the host specificity. Based on sequence analysis, we found that two putative T6SS loci exist in the genome of the avian pathogenic Escherichia coli (APEC) strain TW-XM. To assess the contribution of these two T6SSs to TW-XM pathogenesis, the crucial clpV clusters of these two T6SS loci and their vgrG genes were deleted to generate a series of mutants. Consequently, T6SS1-associated mutants presented diminished adherence to and invasion of several host cell lines cultured in vitro, decreased pathogenicity in duck and mouse infection models in vivo, and decreased biofilm formation and bacterial competitive advantage. In contrast, T6SS2-associated mutants presented a significant decrease only in the adherence to and invasion of mouse brain microvascular endothelial cell (BMEC) line bEnd.3 and brain tissue of the duck infection model. These results suggested that T6SS1 was involved in the proliferation of APEC in systemic infection, whereas VgrG-T6SS2 was responsible only for cerebral infection. Further study demonstrated that VgrG-T6SS2 was able to bind to the surface of bEnd.3 cells, whereas it did not bind to DF-1 (chicken embryo fibroblast) cells, which further proved the interaction of VgrG-T6SS2 with the surface of BMECs.

cStreptococcus suis is an emerging zoonotic pathogen causing severe infections in pigs and humans. In previous studies, 33 serotypes of S. suis have been identified using serum agglutination. Here, we describe a novel S. suis strain, CZ130302, isolated from an outbreak of acute piglet meningitis in eastern China. Strong pathogenicity of meningitis caused by strain CZ130302 was reproduced in the BALB/c mouse model. The strain showed a high fatality rate (8/10), higher than those for known virulent serotype 2 strains P1/7 (1/10) and 9801 (2/10). Cell adhesion assay results with bEnd.3 and HEp2 cells showed that CZ130302 was significantly close to P1/7 and 9801. Both the agglutination test and its complementary test showed that strain CZ130302 had no strong cross-reaction with the other 33 S. suis serotypes. The multiplex PCR assays revealed no specified bands for all four sets used to detect the other 33 serotypes. In addition, genetic analysis of the whole cps gene clusters of all serotypes was performed in this study. The results of comparative genomics showed that the cps gene cluster of CZ130302, which was not previously reported, showed no homology to the gene sequences of the other strains. Especially, the wzy, wzx, and acetyltransferase genes of strain CZ130302 are phylogenetically distinct from strains of the other 33 serotypes. Therefore, this study suggested that strain CZ130302 represents a novel variant serotype of S. suis (designated serotype Chz) which has a high potential to be virulent and associated with meningitis in animals. Streptococcus suis causes meningitis and septicemia in pigs and is also known as a zoonotic agent (1). Human infections of S. suis were first reported in Denmark in 1968 (2). Since then, this pathogen has spread all over the world. The human Streptococcus suis was epidemic in most Europe countries (3, 4), as well as in Asian countries, such as Vietnam and Thailand (5-7). In China, two outbreaks of human streptococcosis have occurred, affecting more than 100 people and causing 39 deaths (8). More and more S. suis infections from China, Thailand, Hong Kong, Taiwan, and Singapore have been reported, which indicates that S. suis has been an important cause of adult meningitis, endocarditis, septicemia, and arthritis in Asia (9).The serotyping of S. suis isolates rests on the basis of the antigenicity of their capsular polysaccharides (CPs); 35 serotypes have been identified by agglutination tests (10). With the development of sequence analysis of 16S rRNA and cpn60 genes in S. suis, the original S. suis serotypes 32 and 34 were reclassified as Streptococcus orisratti (11). Phylogenetic analyses of the cps gene cluster, conserved Wzy polymerase, Wzx flippase, and glycosyltransferase are all taken as important means of classifying a novel serotype (12). Multiplex PCR assays against the specific genes of the cps clusters have also been developed to identify serotypes in S. suis (13)(14)(15).From March to May 2013, strain CZ130302 caused an outbreak of streptococcosis in piglets at ...

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This study provides a foundation for further research on root genetic regulation and molecular breeding with emphasis on correlations among root traits to ensure robust root growth and well-developed root systems. A set of 447 recombinant inbred lines (RILs) derived from a cross between Jingdou23 (cultivar, female parent) and ZDD2315 (semi-wild, male parent) were used to analyze inheritance and detect QTLs related to root traits at the seedling stage using major gene plus polygene mixed inheritance analysis and composite interval mapping. The results showed that maximum root length (MRL) was controlled by three equivalent major genes, lateral root number (LRN) was controlled by two overlapping major genes, root weight (RW) and volume (RV) were controlled by four equivalent major genes. Hypocotyl length (HL) was controlled by four additive main genes, and hypocotyl weight (HW) was controlled by four additive and additive × additive epistatic, major genes; however, polygene effects were not detected in these traits. Shoot weight (SW) was controlled by multi-gene effects, but major gene effects were not detected. Twenty-four QTLs for MRL, LRN, RW, RV, SW, HL, HW were mapped on LG A1 (chromosome 5), LG A2 (chromosome 8), LG B1 (chromosome 11), LG B2 (chromosome 14), LG C2 (chromosome 6), LG D1b (chromosome 2), LG F_1 (chromosome 13), LG G (chromosome 18), LG H_1 (chromosome 12), LG H_2 (chromosome 12), LG I (chromosome 20), LG K_2 (chromosome 9), LG L (chromosome 19), LG M (chromosome 7), LG N (chromosome 3), LG O (chromosome 10), separately. Root traits were shown to have complex genetic mechanisms at the seedling stage, SW was controlled by multi-gene effects, and the other six traits were controlled by major gene effects. It is concluded that correlations among root traits must be considered to improve the development of beneficial root traits.

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