Identification and analysis of differentially expressed genes involved in dark-induced photoperiod response and senescence of soybean leaves by suppression subtractive hybridization

A cDNA subtractive library enriched for dark-induced up-regulated ESTs was constructed by suppression subtractive hybridization(SSH) from leaf tissues of soybean cultivar DongNong L13 treated with short-day(8-h light/16-h dark) and long-day(16-h light/8-h dark) conditions.A total of 148 clones were sequenced,representing 76 unique ESTs which corresponded to about 20% of 738 clones from the cDNA library and showed a significant up-regulation of at least three fold verified by dot blot hybridization.The putative functions of ESTs were predicted by Blastn and Blastx.The 43 differentially expressed genes identified by subtractions were classified according to their putative functions generated by Blast analysis.Genetic functional analysis indicated that putative proteins encoded by these genes were related to diverse functions during organism development,which include biological regulation pathways such as transcription,signal transduction and programmed cell death,protein,nucleic acid and carbohydrate macromolecule degradation,the cell wall modification,primary and secondary metabolism and stress response.Two soybean transcription factors enhanced in SD conditions,GAMYB-binding protein and DNA binding protein RAV cDNAs that may be involved in SD soybean photoperiod response,had been isolated using 5'-and 3'-rapid amplification of cDNA ends(RACE)(Genbank Accession numbers DQ112540 and DQ147914).

Mapping Quantitative Trait Loci Associated with Photoperiod Sensitivity in Maize(Zea mays L.)

Photoperiod sensitivity in maize plays an essential role in utilizing tropic and sub-tropic germplasm to temperate areas. This study aims to identify and map the QTLs responsible for the characteristics measuring photoperiod sensitivity, days from planting to silking （SD）, photoperiod response coefficient of silking （PRC）, and anthesis-silking interval （ASI）. Using the population derived from Zheng 58, photoperiod-insensitive parent, and Ya 8701, photoperiod-sensitive parent, a linkage map was constructed with 93 single sequence repeat （SSR） markers. Phenotyping of 296 F2-3 families of the population in replicated-field test was conducted in both long-day （Beijing, China） and short-day （Sichuan, China） conditions. Ten QTLs were identified to be associated with the SD and ASI on chromosomes 3, 4, 6, 8, and 10 in the longday conditions, and 11 QTLs were detected to be related to the SD and ASI on chromosomes 2, 3, 4, 5, 6, 8, and 10 in the short-day conditions, respectively. A QTL associated with the PRC as a major effect in the long-day conditions located in the same position as the QTL related to the SD and ASI in the map, and was on chromosome 10 linked with marker bnlg1655. Using these QTLs in the marker-assisted selection, the photoperiod sensibility could be reduced by selection of the alleles responsible for the SD, PRC, and ASI in breeding programs.

Cloning and Characterization of Putative Hd6 Ortholog Associated with Zea mays L. Photoperiod Sensitivity

The photoperiod response of lowering is critical to the survival and successful reproduction in crops. The Hd6 gene, encoding a protein similar to the Arabidopsis α-subunit of CASEIN KINASE2α （CK2α） has been reported to affect flowering time through the photoperiodic pathway in rice. In this study, the maize ortholog, ZmHd6, has been cloned and its role in the photoperiodic pathway was investigated. ZmHd6 encodes 332 amino acids with six distinct domains： two CK2 active domains, a nuclear localization signal sequence, a N terminal domain, an ATP binding site, and an active site of serine/threonine protein kinase. ZmHd6 was constitutively expressed in the leaves and shoot apical meristem （SAM） with the highest expression in SAMs of plants with seven leaves under long and short day conditions. Delayed flowering time under long day （LD） conditions were observed in ZmHd6 overexpression transgenic Arabidopsis plants compared to the wild type. In transgenic Arabidopsis plants, ZmHd6 was expressed in a circadian oscillatory pattern, TOC1 peak expression was delayed, new GI, CO, and FT expressions reached to peak after 3 h while entering illumination period and oscillatory expression patterns of CO and FT were created during the dark phase. These results suggested that ZmHd6 might negatively regulate flowering time under LD conditions by delaying TOC1 peak expression and disrupting CO and FT expression in transgenic Arabidopsis plants.

Evaluation of Aegilops tauschii for Heading Date and Its Gene Location in a Re-synthesized Hexaploid Wheat

The successful worldwide cultivation of hexaploid wheat in a diverse range of environments is because of, in part, breeding and selection for appropriate heading date. To adjust and fine-tune the heading time of hexaploid wheat to particular geographical regions and specific environment within these, there is an urgent need to evaluate and use alternative alleles for heading time. Aegilops tauschii, the donor species of D-genome of hexaploid wheat, has a wide geographic distribution. The present study revealed a wide variation for heading time among 56 Ae. tauschii accessions. All the accessions with short heading dates belonged to the ssp. tauschii, whereas most of ssp. strangulata accessions showed very long heading date. The heading date was also related to distribution of this species. The monotelosomic and monosomic analysis of a synthetic hexaploid wheat showed that chromosome 2D derived from ssp. tauschii accession AS60 had a major effect on promoting heading time with a reduction of more than 5 days. It is postulated that this Ae. tauschii genotype possess the allele Ppd-D^t1 responsible for the insensitivity to photoperiod. This allele is probably different from Ppd-D1 existing in hexaploid wheat. The new allele Ppd-D^t1 derived from Ae. tauschii might be used as a source for hexaploid wheat breeding on photoperiod response.

Genetic analysis and QTL mapping of growth period traits and plant height traits in soybean recombinant inbred lines from Dongnong 47 × PI 317334-B

High and stable yield is the main goal of soybean genetic improvement.In this study,association analysis was used to detect the quantitative trait loci(QTL)for the plant height,and soybean growth period using 182 SSR markers in the RIL population of 136 F_(4:8) lines,which developed from a cross between photoperiod-insensitive cultivar‘Dongnong 47’and photoperiod-sensitive variety PI317334–B.The results showed that 33 QTLs related to soybean growth period and plant height traits were detected by compound interval mapping,and were located on 12 linkage groups including N,C1,C2,J,D1a,B2,E,G,A2,O,L,I,with the contribution rate of 7.85–33.84%.These QTL loci and linkage markers related to soybean photoperiod sensitivity,would be helpful to identify key genes that control soybean photoperiod sensitivity,and provide an important basis for the breeding of new photoperiod-insensitive soybean varieties based on molecular design breeding.

Shaping polyploid wheat for success:Origins,domestication,and the genetic improvement of agronomic traits

Bread wheat(Triticum aestivum L.,AABBDD,2 n=6 x=42),which accounts for most of the cultivated wheat crop worldwide,is a typical allohexaploid with a genome derived from three diploid wild ancestors.Bread wheat arose and evolved via two sequential allopolyploidization events and was further polished through multiple steps of domestication.Today,cultivated allohexaploid bread wheat has numerous advantageous traits,including adaptive plasticity,favorable yield traits,and extended end-use quality,which have enabled its cultivation well beyond the ranges of its tetraploid and diploid progenitors to become a global staple food crop.In the past decade,rapid advances in wheat genomic research have considerably accelerated our understanding of the bases for the shaping of complex agronomic traits in this polyploid crop.Here,we summarize recent advances in characterizing major genetic factors underlying the origin,evolution,and improvement of polyploid wheats.We end with a brief discussion of the future prospects for the design of gene cloning strategies and modern wheat breeding.