Overexpression of a New Zinc Finger Protein Transcription Factor OsCTZFP8 Improves Cold Tolerance in Rice.

Cold stress is one of the most important abiotic stresses in rice. C2H2 zinc finger proteins play important roles in response to abiotic stresses in plants. In the present study, we isolated and functionally characterized a new C2H2 zinc finger protein transcription factor OsCTZFP8 in rice. OsCTZFP8 encodes a C2H2 zinc finger protein, which contains a typical zinc finger motif, as well as a potential nuclear localization signal (NLS) and a leucine-rich region (L-box). Expression of OsCTZFP8 was differentially induced by several abiotic stresses and was strongly induced by cold stress. Subcellular localization assay and yeast one-hybrid analysis revealed that OsCTZFP8 was a nuclear protein and has transactivation activity. To characterize the function of OsCTZFP8 in rice, the full-length cDNA of OsCTZFP8 was isolated and transgenic rice with overexpression of OsCTZFP8 driven by the maize ubiquitin promoter was generated using Agrobacterium-mediated transformation. Among 46 independent transgenic lines, 6 single-copy homozygous overexpressing lines were selected by Southern blot analysis and Basta resistance segregation assay in both T1 and T2 generations. Transgenic rice overexpressing OsCTZFP8 exhibited cold tolerant phenotypes with significantly higher pollen fertilities and seed setting rates than nontransgenic control plants. In addition, yield per plant of OsCTZFP8-expressing lines was significantly (p < 0.01) higher than that of nontransgenic control plants under cold treatments. These results demonstrate that OsCTZFP8 was a C2H2 zinc finger transcription factor that plays an important role in cold tolerance in rice.

[Screening probiotic endophytic bacteria from medicinal plant flex cornuta and the phytopathogen-inhibiting effect].

Culturable endophytic bacteria were isolated from medicinal plant Ilex cornuta by plate-spreading method, strains with strong inhibitory effect on phytopathogen were screened by confrontation culture and fermentation filtrate culture methods, and the morphological changes of phytopathogen hyphae treated with endophytic bacteria were examined by microscopy and micrograph. Their phylogenetic relationships were determined by homology analysis of the 16S rDNA sequences of PCR products and the taxonomic status of the selected strains was determined based on their morphology, physiology, biochemical test results and 16S rDNA sequence analysis. A total of 85 endophytic bacteria were isolated from the healthy roots, stems, leaves and fruits of I. cornuta, and 10 strains of them showed strong inhibitory effect on Alternaria alternata, Magnaporthe grisea, Fusarium oxysporum, and were preliminarily identified belonging to four genera and seven species. Three strains with the strongest inhibitory effect, GG78 (60.3%), GG31 (48.1%) and GG13 (61.0%) belonged to Enterobacter cloacae, Enterobacter ludwigii and Bacillus cereus, respectively. Microscopic analyses showed that the inhibited phytopathogen hyphae became deformed, distorted, and partially expanded forming plasma concentration and hair-like branch on the hyphae base. These morphological changes could be caused by the extracellular metabolic substances secreted by the endophytic bacteria, such as antibiotics, hydrolytic enzymes, alkaloids and so on.

Paper-based electroanalytical devices for in situ determination of salicylic acid in living tomato leaves.

Detection of phytohormones in situ has gained significant attention due to their critical roles in regulating developmental processes and signaling for defenses in plants at low concentration. As one type of plant hormones, salicylic acid has recently been found to be one of pivotal signal molecules for physiological behaviors of plants. Here we report the application of paper-based electroanalytical devices for sensitively in situ detection of salicylic acid in tomato leaves with the sample volume of several microliters. Specifically, disposable working electrodes were fabricated by coating carbon tape with the mixture of multiwall carbon nanotubes and nafion. We observed that the treatment of the modified carbon tape electrodes with oxygen plasma could significantly improve electrochemical responses of salicylic acid. The tomato leaves had a punched hole of 1.5mm diameter to release salicylic acid with minor influence on continuous growth of tomatoes. By incorporating the tomato leaf with the paper-based analytical device, we were able to perform in situ determination of salicylic acid based on its electrocatalytic oxidation. Our experimental results demonstrated that the amounts of salicylic acid differed statistically in normal, phytoene desaturase (PDS) gene silent and diseased (infected by Botrytis cinerea) tomato leaves. By quantifying salicylic acid at the level of several nanograms in situ, the simple paper-based electroanalytical devices could potentially facilitate the study of defense mechanism of plants under biotic and abiotic stresses. This study might also provide a sensitive method with spatiotemporal resolution for mapping of chemicals released from living organisms.

Identification of quantitative trait loci for cadmium accumulation and distribution in rice (Oryza sativa).

Cadmium (Cd) poses a serious risk to human health due to its biological concentration through the food chain. To date, information on genetic and molecular mechanisms of Cd accumulation and distribution in rice remains to be elucidated. We developed an independent F7 RIL population derived from a cross between two japonica cultivars with contrasting Cd levels, 'Suwon490' and 'SNU-SG1', for QTLs identification of Cd accumulation and distribution. 'Suwon490' accumulated five times higher Cd in grain than 'SNU-SG1'. Large genotypic variations in Cd accumulation (17-fold) and concentration (12-fold) in grain were found among RILs. Significant positive correlations between Cd accumulation in grain with shoot Cd accumulation and shoot to grain distribution ratio of Cd signify that both shoot Cd accumulation and shoot to grain Cd distribution regulate Cd accumulation in japonica rice grain. A total of five main effect QTLs (scc10 for shoot Cd accumulation; gcc3, gcc9, gcc11 for grain Cd accumulation; and sgr5 for shoot to grain distribution ratio) were detected in chromosomes 10, 3, 9, 11, and 5, respectively. Of these, the novel potential QTL sgr5 has the strongest effect on shoot to grain Cd distribution. In addition, two digenic epistatic interaction QTLs were identified, suggesting the substantial contribution of nonallelic genes in genetic control of these Cd-related traits.

Population-specific quantitative trait loci mapping for functional stay-green trait in rice (Oryza sativa L.).

The functional stay-green trait gives leaves a longer duration of greenness and photosynthetic capacity during the grain-filling period. We developed two independent recombinant inbred line populations from the intra- and intersubspecific crosses of Oryza sativa L. subsp. japonica 'Suweon490' (japonica) × O. sativa subsp. japonica 'SNU-SG1' (japonica) and O. sativa subsp. indica 'Andabyeo' (indica) × O. sativa subsp. japonica 'SNU-SG1' (japonica), respectively. The common parental line 'SNU-SG1' was the functional source for the stay-green trait. Quantitative trait locus (QTL) mapping based on simple sequence repeat markers identified a total of six QTLs associated with two stay-green traits across two populations. The two traits were cumulative chlorophyll content (SPAD value) of flag leaf (CSFL) and total cumulative SPAD value of the four upper leaves (TCS). Four QTLs, tcs4, csfl6, csfl9 (or tcs9), and csfl12, located on chromosomes 4, 6, 9, and 12, respectively, were detected simultaneously in both populations. The remaining two QTLs, csfl2 (or tcs2) and tcs5, on chromosomes 2 and 5, respectively, were found to be population specific. Moreover, the functional stay-green trait of 'SNU-SG1' positively correlated with grain yield performance. Two yield QTLs, yld6 and yld9, on chromosomes 6 and 9 found in both populations were positioned at the same locations with the csfl6 and tcs9 QTLs for stay-green traits. Thus, the identified chromosomal regions can be promising targets of marker-assisted introgression of the functional stay-green trait into breeding materials for improvement of rice yield.