GmSYP24, a putative syntaxin gene, confers osmotic/drought, salt stress tolerances and ABA signal pathway.

As major environment factors, drought or high salinity affect crop growth, development and yield. Transgenic approach is an effective way to improve abiotic stress tolerance of crops. In this study, we comparatively analyzed gene structures, genome location, and the evolution of syntaxin proteins containing late embryogenesis abundant (LEA2) domain. GmSYP24 was identified as a dehydration-responsive gene. Our study showed that the GmSYP24 protein was located on the cell membrane. The overexpression of GmSYP24 (GmSYP24ox) in soybean and heteroexpression of GmSYP24 (GmSYP24hx) in Arabidopsis exhibited insensitivity to osmotic/drought and high salinity. However, wild type soybean, Arabidopsis, and the mutant of GmSYP24 homologous gene of Arabidopsis were sensitive to the stresses. Under the abiotic stresses, transgenic soybean plants had greater water content and higher activities of POD, SOD compared with non-transgenic controls. And the leaf stomatal density and opening were reduced in transgenic Arabidopsis. The sensitivity to ABA was decreased during seed germination of GmSYP24ox and GmSYP24hx. GmSYP24hx induced up-regulation of ABA-responsive genes. GmSYP24ox alters the expression of some aquaporins under osmotic/drought, salt, or ABA treatment. These results demonstrated that GmSYP24 played an important role in osmotic/drought or salt tolerance in ABA signal pathway.

Screening Chinese soybean genotypes for Agrobacterium-mediated genetic transformation suitability.

The Agrobacterium-mediated transformation system is the most commonly used method in soybean transformation. Screening of soybean genotypes favorable for Agrobacterium-infection and tissue regeneration is the most important step to establish an efficient genetic transformation system. In this study, twenty soybean genotypes that originated from different soybean production regions in China were screened for transient infection, regeneration capacity, and stable transgenic efficiency. Three genotypes, Yuechun 04-5, Yuechun 03-3, and Tianlong 1, showed comparable stable transgenic efficiencies with that of the previously reported American genotypes Williams 82 and Jack in our experimental system. For the Tianlong 1, the average stable transformation efficiency is 4.59%, higher than that of control genotypes (Jack and Williams 82), which is enough for further genomic research and genetic engineering. While polymerase chain reaction (PCR), LibertyLink strips, and ß-glucuronidase (GUS) staining assays were used to detect the insertion and expression of the transgene, leaves painted with 135 mg/L Basta could efficiently identify the transformants.

Large-scale sequencing of normalized full-length cDNA library of soybean seed at different developmental stages and analysis of the gene expression profiles based on ESTs.

Although GenBank has now covered over 1,400,000 expressed sequence tags (ESTs) from soybean, most ESTs available to the public have been derived from tissues or environmental conditions rather than developing seeds. It is absolutely necessary for annotating the molecular mechanisms of soybean seed development to analyze completely the gene expression profiles of its immature seed at various stages. Here we have constructed a full-length-enriched cDNA library comprised of a total of 45,408 cDNA clones which cover various stages of soybean seed development. Furthermore, we have sequenced from 5' ends of these clones, 36,656 ESTs were obtained in the present study. These EST sequences could be categorized into 27,982 unigenes, including 22,867 contigs and 5,115 singletons, among which 27,931 could be mapped onto soybean 20 chromosome sequences. Comparative genomic analysis with other plants has revealed that these unigenes include lots of candidate genes specific to dicot, legume and soybean. Approximately 1,789 of these unigenes currently show no homology to known soybean sequences, suggesting that many represent mRNAs specifically expressed in seeds. Novel abundant genes involved in the oil synthesis have been found in this study, may serve as a valuable resource for soybean seed improvement.