Chen Shouyi

Identification, inheritance and QTL mapping of root traits related to tolerance to rhizo-spheric stresses in soybean (G. max (L.) Merr.)

A sample of soybean accessions (Glycine max (L.) Merr.) from Huanghe-Huaihe-Haihe and Middle-Lower Changjiang Valleys in China was used to identify their tolerance to rhizo-spheric stresses, including drought, aluminum toxin and low phosphorus. A total of 15 accessions highly tolerant to at least one of the abiotic stresses were screened out. The correlation between drought tolerance and the relative values of total root length, root volume and dry root weight (relative to dry plant weight) were all significant at 0.01 level, respectively. So did for the correlation between aluminum toxin tolerance and the stress to non-stress ratios of the number of lateral roots, tap root length, total root length, root volume and dry root weight. The inheritance study on the above three root traits related to drought tolerance under segregation analysis indicated that between the two parents of the recombinant inbred line (RIL) population of (Kefeng 1 × Nannong 1138-2), the relative values of dry root weight, total root length and root volume were controlled by two major genes plus polygenes with their major gene heritability values 62.26%–91.81% and polygene heritability values 2.99%–24.75%, respectively, and for the latter two traits, the two major genes linked together with recombination value 4.30% and 1.93%, respectively. The inheritance study on the five root traits related to aluminum toxin tolerance revealed that between the two parents of the recombinant inbred line (RIL) population of (Bogao × NG94-156), the stress to non-stress ratios of lateral root number, tap root length, total root length and dry root weight were controlled by three major genes plus polygenes with their major gene heritability values 80.22%–91.81% and polygene heritability values 3.52%–11.39%, while the stress to non-stress ratio of root volume was controlled by three major genes with their major gene heritability value 93.44%. The (Kefeng 1 × Nannong 1138-2) RIL population was also used for mapping QTLs of relative dry root weight, total root length and root volume related to drought tolerance. Five, three and five QTLs located on Linkage group N6-C2, N8-D1b+W, N11-E and N18-K for each of the three traits, respectively, were identified. Each of the traits appeared to have one locus (Dw1, Rl1, Rv1) with relatively large effect in comparison with their other loci, and the three loci in above parentheses were located in the same region STAS8_3T-STAS8_6T on N6-C2 with a same distance to the flanking markers. Thus, Dw1, Rl1, and Rv1 even might be a same locus and performed as pleiotropic of a same gene. The results between segregation analysis and QTL mapping appeared relatively consistent, therefore could be used for verification each other.

RAPD tagging of a salt tolerant gene in rice

A salt tolerant rice mutant was obtained through tissue culture. The inheritance of salt tolerance in F2 population of mutant crossed with its original variety under salt stress was studied. According to the standard, the ratio of salt tolerant: sensitive was about 3:1 suggesting that there was a major gene related to salt tolerance in the mutant. By RAPD analysis with 220 10-mer primers, the gene was tagged by a 1.0 kb DNA fragment named OPS12-10 which was located on chromosome 7. The genetic distance between the major salt tolerant gene was 16.4 cm.

WRKY transcription factor superfamily: Structure, origin and functions

WRKY transcription factors are transcriptional regulatory factors in which N-terminal ends contain the WRKYGQR amino acid sequence and a zinc-finger motif. WRKY transcription factors can regulate the expression of target genes that contain the W-box elements (C/T)TGAC(C/T) in the promoter regions by specifically binding to the (C/T)TGAC(C/T) sequence. WRKY transcription factors regulate the expression of pathogen-induced, senescence-induced, abscisic acid (ABA)-induced, gibberellic acid (GA)-induced and salcylic acid (SA)-induced genes and play an important role in the regulation of plant growth and development as well as in their response to many kinds of biotic and abiotic stress. The progress of research on the basic structure, origin and biological function of plant WRKY transcription factor in recent years was reviewed in this paper.

Density-enhanced genetic linkage map of RIL population NJRIKY and its impacts on mapping genes and QTLs in soybean.

A high-density genetic linkage map with informative markers is essential for plant genome analysis,including gene mapping,identification of quantitative trait locus (QTL),map-based cloning,and physical map construction.Though four genetic linkage maps for the recombinant inbred line population NJRIKY derived from (Kefeng 1×Nannong 1138-2) have been established already,there are still problems of precision and accuracy in mapping genes and QTLs due to insufficiency of genetic information and number of markers.A total of 401 polymorphic SSR markers were screened out from 967 ones for density-enhancement of the previous maps.Along with other marker data,a new genetic linkage map was constructed by using Mapmaker/Exp 3.0b,with 553 markers,including 316 SSR,197 RFLP,39 EST and one morphologic markers,spanning 25 linkage groups,covering total length 2 071.6 cM of the soybean genome,with an average marker interval distance of 3.70 cM.In comparison with the old map,the number of gaps larger than 20 cM decreased from forty-two to two on the enhanced map.Using this map to relocate the seven SMV resistant genes,Rsc-3,Rsc-7,Rsc-9,Rsc-13,Rsa,Rn1,and Rn3 were mapped on LG D1b again with distances to the flanking markers all less than 6 cM,among them,Rsc-9,Rn1,and Rsa less than 1 cM and Rsc-13 co-segregating with EST-SSR marker GMKF168a.After re-mapping the QTLs for eight agronomic traits,42 QTLs were detected on 12 linkage groups,with 20 of them accounted for more than 10% of the total variation,respectively,and their marker intervals obviously shortened.

Tobacco floral homeotic gene homologues: partial sequence and expression pattern

Using PCR approach, three cDNA sequences. NTSQUA4, NTSQUA12 and NTSQUA15, were amplified from firststrand cDNAs of wild tobacco flower buds and identified as homologues for floral homeotic genes. All the three clones contained domains that a floral homeotic gene generally had, i.e. I domain, K domain and C-terminal domain except MADS box since the PCR primers were designed beyond this region. In addition, the amino acid sequences of them showed 50%–60% identity (70% –80% similarity) with the known floral organ identity class A gene AP1 and SQUA, possibly indicating that they are class A-like genes. NTSQUA4 and NTSQUA412 shared 95% identity in their amino acid sequence, while NTSQUA415 exhibited only 47% identity as compared with NTSQUA4 and NTSQUA12. Within tobacco flower, NTSQUA4 was expressed in sepals, petals and carpels, but not in stamens, while NTSQUAl5 wah expressed in every whorl of the flower. The possible functions of these genes are discussed.

Cloning, expression and characterization of a nucleoside diphosphate kinase (NDPK) gene from tobacco

Abstract Nucleoside diphosphate kinase (NDPK) is a housekeeping enzyme that maintains the intracellular levels of all (d)NTPs used in biosynthesis except ATP. Here we report that a full-length cDNA encoding nucleoside diphosphate kinase (NDPK) was cloned using yeast two-hybrid approach. A tobacco NDPK gene was obtained and designated as NtNDPK1. NtNDPK1 is 704 bp in length and encodes a putative 16.2 kD protein of 148 amino acids. Phylogenic analysis showed that NtNDPK1 is highly homologous to other plant NDPK genes and identified as type i (NDPK1). RNA-gel blot analysis showed that there was no significant difference of NtNDPK1 expression in roots, stems, leaves and buds. And expression of NtNSPK1 was induced by ABA and PEG and repressed by NaCl, but not significantly affected by Paraquat, wounding and low temperature (4°C) treatments, indication that NtNDPK1 may play a certain role in response to abiotic stress. In vitro phosphorylation assay demonstrated that NtNDPK1 had autophosphorylation activity. *...

Genomic cloning and sequencing of betaine aldehyde dehydrogenase gene in spinach

A genornic library derived from leaves of spinach was constructed with the λGeml1-BamHI Arms as the vector. The library was screened using thc BADH cDNA of mountiain spinach as a probe and six positive clones were obtained through three rounds of screening. One of the positive clones named D, which was hybridized with the 5’600 bp fragment of mountain spinach BADH cDNA, was sclcctrd and further analyzed. The size of the insert in clone D was about 12 kb. 8 856 nucleotides of the insert were sequenced which contained 2 459 nucleotides of 5′ noncoding region, 6 111 nucleotides of the complete sequence of the BADH gene, and 286 nuclrotides of a 3′ noncoding rcgion. The result of sequence analysis indicated that the BADH gene contained 14 introns and the junction scquenccs at splicing sites followed the GT-AG rule basically.