Genome editing of a rice CDP-DAG synthase confers multipathogen resistance.

The discovery and application of genome editing introduced a new era of plant breeding by giving researchers efficient tools for the precise engineering of crop genomes1. Here we demonstrate the power of genome editing for engineering broad-spectrum disease resistance in rice (Oryza sativa). We first isolated a lesion mimic mutant (LMM) from a mutagenized rice population. We then demonstrated that a 29-base-pair deletion in a gene we named RESISTANCE TO BLAST1 (RBL1) caused broad-spectrum disease resistance and showed that this mutation caused an approximately 20-fold reduction in yield. RBL1 encodes a cytidine diphosphate diacylglycerol synthase that is required for phospholipid biosynthesis2. Mutation of RBL1 results in reduced levels of phosphatidylinositol and its derivative phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). In rice, PtdIns(4,5)P2 is enriched in cellular structures that are specifically associated with effector secretion and fungal infection, suggesting that it has a role as a disease-susceptibility factor3. By using targeted genome editing, we obtained an allele of RBL1, named RBL1Δ12, which confers broad-spectrum disease resistance but does not decrease yield in a model rice variety, as assessed in small-scale field trials. Our study has demonstrated the benefits of editing an LMM gene, a strategy relevant to diverse LMM genes and crops.

Genetic analysis and fine mapping of a novel semidominant dwarfing gene LB4D in rice.

A dwarf mutant, designated LB4D, was obtained among the progeny of backcrosses to a wild rice introgression line. Genetic analysis of LB4D indicated that the dwarf phenotype was controlled by a single semidominant dwarfing gene, which was named LB4D. The mutants were categorized as dn-type dwarf mutants according to the pattern of internode reduction. In addition, gibberellin (GA) response tests showed that LB4D plants were neither deficient nor insensitive to GA. This study found that tiller formation by LB4D plants was decreased by 40% compared with the wild type, in contrast to other dominant dwarf mutants that have been identified, indicating that a different dwarfing mechanism might be involved in the LB4D dominant mutant. The reduction of plant height in F(1) plants ranged from 27.9% to 38.1% in different genetic backgrounds, showing that LB4D exerted a stronger dominant dwarfing effect. Using large F(2) and F(3) populations derived from a cross between heterozygous LB4D and the japonica cultivar Nipponbare, the LB4D gene was localized to a 46 kb region between the markers Indel 4 and Indel G on the short arm of chromosome 11, and four predicted genes were identified as candidates in the target region.

The role of sterile chitosan-based dressing in reducing complications related to a peripherally inserted central catheter in patients with hematological tumors.

BACKGROUND: Intravenous chemotherapy is one of the most common treatments for hematological tumors, a major threat to human health and life. Due to its safety, comfort, and convenience, a peripherally inserted central catheter (PICC) is the preferred route of administration of intravenous chemotherapy. However, some PICC-related complications are drawing increasing attention. In this study, we investigated the use and role of sterile chitosan-based dressing in PICC-related complications in patients with hematological tumors. METHODS: We retrospectively analyzed the clinical data of 205 patients with hematological tumors who had a PICC placed. The patients were divided into two groups, the observation group (sterile chitosan-based dressing, n=105) and the control group (sterile gauze dressing; n=100). The incidences of bleeding, infection, poor healing, and phlebitis, as well as the risk of bleeding, infection, and poor healing at the puncture site within a week of PICC placement, were analyzed. RESULTS: The overall incidences of bleeding, infection, and poor healing were, respectively, 42.9%, 6.7%, and 6.7% in the observation group and 63.0%, 22.0%, and 34% in the control group (all P<0.05). The risk of local bleeding was significantly lower in the observation group than in the control group [odds ratio (OR) 0.366; 95% confidence interval (CI): 0.211-0.634; P<0.001]. The risk of local bleeding was significantly higher in the platelets <50×109/L group than in the platelets >100×109/L group (OR 3.068; 95% CI: 1.397-6.740; P=0.005), while no significant difference was observed in the risk of bleeding between the platelets 50×109-100×109/L group and the platelets >100×109/L group (OR 0.839; 95% CI: 0.404-1.742; P=0.638). The risk of infection (OR 0.214; 95% CI: 0.088-0.522; P<0.001) and the risk of poor healing (OR 0.139; 95% CI: 0.058-0.331; P<0.001) were significantly lower in the observation group than in the control group. CONCLUSIONS: For patients with hematological tumors, sterile chitosan-based dressing after PICC placement reduces the risk of bleeding and infection and promotes healing at the puncture site.

Abscisic Acid Regulates Auxin Distribution to Mediate Maize Lateral Root Development Under Salt Stress.

Roots are important plant organs. Lateral root (LR) initiation (LRI) and development play a central role in environmental adaptation. The mechanism of LR development has been well investigated in Arabidopsis. When we evaluated the distribution of auxin and abscisic acid (ABA) in maize, we found that the mechanism differed from that in Arabidopsis. The distribution of ABA and auxin within the primary roots (PRs) and LRs was independent of each other. Auxin localization was observed below the quiescent center of the root tips, while ABA localized at the top of the quiescent center. Furthermore, NaCl inhibited LRI by increasing ABA accumulation, which mainly regulates auxin distribution, while auxin biosynthesis was inhibited by ABA in Arabidopsis. The polar localization of ZmPIN1 in maize was disrupted by NaCl and exogenous ABA. An inhibitor of ABA biosynthesis, fluridone (FLU), and the ABA biosynthesis mutant vp14 rescued the phenotype under NaCl treatment. Together, all the evidence suggested that NaCl promoted ABA accumulation in LRs and that ABA altered the polar localization of ZmPIN1, disrupted the distribution of auxin and inhibited LRI and development.

Phenotypic characterization, genetic analysis and gene-mapping for a brittle mutant in rice.

Plant mechanical strength is an important agronomic trait of rice. An ethyl methane sulfonate (EMS)-induced rice mutant, fragile plant 2 (fp2), showed morphological changes and reduced mechanical strength. Genetic analysis indicated that the brittle of fp2 was controlled by a recessive gene. The fp2 gene was mapped on chromosome 10. Anatomical analyses showed that the fp2 mutation caused the reduction of cell length and cell wall thickness, increasing of cell width, and the alteration of cell wall structure as well as the vessel elements. The consequence was a global alteration in plant morphology. Chemical analyses indicated that the contents of cellulose and lignin decreased, and hemicelluloses and silicon increased in fp2. These results were different from the other mutants reported in rice. Thus, fp2 might affect the deposition and patterning of microfibrils, the biosynthesis and deposition of cell wall components, which influences the formation of primary and secondary cell walls, the thickness of cell walls, cell elongation and expansion, plant morphology and plant strength in rice.

Genetic analysis and gene mapping of purple stigma in rice.

A new double-haploid (rdh) rice plant with purple stigma and red seeds was discovered by tissue culture. Genetic analysis suggested that the trait of rdh purple stigma was controlled by a pair of dominant gene. Polymorphic analysis of microsatellite markers demonstrated that the purple stigma gene of rdh was located on rice chromosome 6 at 4.2 cM, 0.35 cM and 0.53 cM from microsatellite markers RM276, RM253 and RM111, respectively. It was believed that the purple stigma gene of rdh was the first mapped purple stigma gene on rice chromosome 6. This purple stigma gene was designated tentatively as Ps-4.

Evolutionary Comparison of Two Combinatorial Regulators of SBP-Box Genes, MiR156 and MiR529, in Plants.

A complete picture of the evolution of miRNA combinatorial regulation requires the synthesis of information on all miRNAs and their targets. MiR156 and miR529 are two combinatorial regulators of squamosa promoter binding protein-like (SBP-box) genes. Previous studies have clarified the evolutionary dynamics of their targets; however, there have been no reports on the evolutionary patterns of two miRNA regulators themselves to date. In this study, we investigated the evolutionary differences between these two miRNA families in extant land plants. Our work found that miR529 precursor, especially of its mature miRNA sequence, has a higher evolutionary rate. Such accelerating evolution of miR529 has significantly effects on its structural stability, and sequence conservation against existence of itself. By contrast, miR156 evolves more rapidly in loop region of the stable secondary structure, which may contribute to its functional diversity. Moreover, miR156 and miR529 genes have distinct rates of loss after identical duplication events. MiR529 genes have a higher average loss rate and asymmetric loss rate in duplicated gene pairs, indicating preferred miR529 gene losses become another predominant mode of inactivation, that are implicated in the contraction of this family. On the contrary, duplicated miR156 genes have a low loss rate, and could serve as another new source for functional diversity. Taken together, these results provide better insight into understanding the evolutionary divergence of miR156 and miR529 family in miRNA combinational regulation network.

[Rapid establishment of suspension cell lines in japonica rice].

With Jingkang No.5 (PiA), calli of the PiA induced for 10-15 days were transferred into amino acid liquid culture medium, to establish excellent rice suspension cell lines successfully in a relative short time. The growth characteristics and differentiation conditions of suspension cells were measured at different phases. Results revealed that the optimal subculture time was 7-10 days, and the cells cultured for 30-120 days had the best differentiation ability (57.1%) and regeneration ability (20%). This study is promising in further using the suspension cell for genetic transformation and protoplasm isolation.

Morphological, anatomical and genetic analysis for a rice mutant with abnormal hull.

A mutant with abnormal hull was first discovered from a twin-seedling strain W2555 in rice (Oryza sativa L.). The mutant had sparse branches and decreased number of florets from the base to the peak. Frequently, the florets at the top of the panicle did not develop completely. The underdeveloped florets often showed slender and white in their life cycle. Genetic analysis indicated that the mutant traits were controlled by a single recessive gene (temporarily designated as ah). ah gene controlled the development of inflorescence meristem and the flower organ. The florets of mutant showed degenerated lemma and palea. Stamens and lodicules were homeoticly transformed into pistils and palea/lemma-like structures, respectively. It seemed that ah mutant phenotypes of the homeotic conversions in lodicules and stamens were very similar to that of the B loss-of-function spw1 gene reported previously in rice.