[Advances in plant microRNA and stresses response.].

MicroRNAs (miRNAs) are endogenous 16-29 nt non-coding small RNAs that were are generally found in species and typically encoded by endogenous genes. They play an important regulatory role at post-transcription level by targeting mRNA cleavage and translation repression. More and more plant miRNAs had been predicted and identified along with the development of bioinformatics and experimental techniques. At stress conditions, plant miRNAs also play a role in adaptation by up-regulating or down-regulating the miRNA expression. The biogenesis, action mode with target genes, bio-logical functions of plant miRNAs, as well as the stress-responsive miRNAs, were reviewed and the methodologies of miRNA study were also briefly summarized in this paper.

[QTL mapping of plant height and ear position in maize (Zea mays L.)].

A molecular linkage map for the maize hybrid of cross between Ye478 and Dan340 was constructed by using 150 co-dominant SSR markers. The total map length was 1 478.7 cM with an average interval of 10.0 cM. Composite interval mapping was used to identify the plant height (PH) and ear position (EH) QTL at 5 environments based on the phenotypic data of 397 F2:3 families. Then 21 PH and 25 EH relevant QTL were identified. The mean contribution of 12.2% and 14.9% QTL for plant height was identified at the interval of umc2025 - umc1035 on chromosome 1 and umc1822 - bnlg1118 on chromosome 5, respectively. Meanwhile, the mean contribution of 10.2% and 22.8% to ear position were identified at the interval of phi029 - umc1102 on chromosome 3 and phi109188 - bnlg1118 on chromosome 5. The main QTL for PH and EH were both found at the regions of Bin5.05 - 5.07 on chromosome 5. The additive and partial dominant effects were the main genetic basis for plant height and ear position in maize. The effect of population size and environments on QTL mapping were analyzed.

[Comparative QTL mapping of resistance to sugarcane mosaic virus in maize based on bioinformatics].

The development of genomics and bioinformatics offers new tools for comparative gene mapping. In this paper, an integrated QTL map for Sugarcane mosaic virus (SCMV) resistance in maize was constructed by compiling a total of 81 QTL loci available with the Genetic Map IBM2 2005 Neighbors as reference. These 81 QTL loci were scattered on 7 chromosomes of maize, and most of them was clustered on chromosome 3 and 6. By using meta- analysis method, we identified one and two "consensus QTLs" on chromosomes 3 and 6, respectively. These three QTLs cover the genetic distances of 6.44 cM, 6.16 cM and 27.48 cM on the genetic map IBM2 2005 Neighbors, respectively. Four positional candidate resistant genes were identified within the "consensus QTL" on chromosome 3 via comparative genomics strategy. These results suggested that application of the combined meta-analysis within a species with sequence homologous comparison in a related model plant is an efficient approach to identify the major QTL and its candidate gene(s) for the target traits. The results of this study provided useful information for identifying and cloning of the major gene(s) conferring resistance to SCMV in maize.

[Construction of a SSR linkage map and mapping of quantitative trait loci (QTL) for leaf angle and leaf orientation with an elite maize hybrid].

Maize (Zea mays L.) breeders have begun selecting for more compact plants for higher density planting in order to increase yield per unit area. Leaf angle and leaf orientation are very important traits affecting maize plant type (compactness). In this study, a genetic linkage map containing 138 simple sequence repeat (SSR) markers was constructed based on a mapping population consisting of 500 F2 individuals from the cross between inbred lines Ye478 and Dan340. This SSR linkage map spans a total of 1 394.9 cM with an average interval of 10.1 cM. Quantitative trait loci (QTL) for leaf angle and leaf orientation were identified in 397 F2:3 families. Six QTL for leaf angle were detected that could explain 41.0% of the phenotypic variation; while, eight QTL were detected for leaf orientation that could explain 60.8% of the phenotypic varia-tion. Single QTL contribution to phenotypic variation ranged from 2.9% to 13.6%. Additive and partial dominance were the main genetic effects for leaf angle and leaf orientation; in addition, nine pairs of locus interactions were detected for the two traits, indicating that epistatic interactions at the two-loci level also play a measurable role in the genetic basis of the two traits.

[Progress of chlamydomonas as a model organism].

The unicellular alga Chlamydomonas offers a simple life cycle, easy culture and isolation of series of mutants, established the techniques and tool kit for molecular genetics and genetics analysis. It is now becoming the model organism for studies on photosynthesis in plant, flagellar assembly and function, cell cycle and circadian rhythms, signal transduction, light perception and cell recognition. It is summarized the progress of study on Chlamydomonas as a model organism in this paper.

Comparison of base substitutions in response to nitrogen ion implantation and 60Co-gamma ray irradiation in Escherichia coli

To identify the specificity of base substitutions, a novel experimental system was established based on rifampicin-resistant (Rif r) mutant screening and sequencing of the defined region of the rpoB gene in E. coli. We focused on comparing mutational spectra of base substitutions induced by either low energy nitrogen ion beam implantation or 60Co-gamma rays. The most significant difference in the frequency of specific kinds of mutations induced by low energy nitrogen ion beam was that CG -> TA transitions were significantly increased from 32 to 46, AT -> TA transversions were doubled from 7 to 15 in 50 mutants, respectively. The preferential base substitutions induced by nitrogen ion beam implantation were CG -> TA transitions, AT -> GC transitions, AT -> TA transversions, which account for 92.13 percent (82/89) of the total. The mutations induced by 60Co-gamma rays were preferentially GC -> AT and AT -> GC transitions, which totaled 84.31 percent (43/51).