Two novel eukaryotic translation initiation factor 5A genes from Populus simonii×P.nigra confer tolerance to abiotic stresses in Saccharomyces cerevisiae

The role of plant eIF5A proteins in multiple biological processes, such as protein synthesis regulation, translation elongation, mRNA turnover, programmed cell death and stress tolerance is well known. Toward using these powerful proteins to increase stress tolerance in agricultural plants, in the present study, we cloned and characterized PsneIFSA2 and PsneIFSA4 from young poplar （P. simonii × P. nigra） leaves. The deduced amino acid sequences of PsneIF5A2 and PsneIF5A4 were 98 % similar to each other, and they are orthologs of eIF5A 1 in Arabidopsis. In a subcellular localization analysis, PsneIF5A2 and PsneIF5A4 proteins were localized in the nucleus and cytoplasm, qRT-PCR analysis showed that PsneIF5A2 and PsneIF5A4 were transcribed in poplar flowers, stem, leaves, and roots. In addition, they were also induced by abiotic stresses. Transgenic yeast expressing PsneIF5A2 and PsneIF5A4 had increased salt, heavy metal, osmotic, oxidative tolerance. Our results suggest that PsneIF5A2 and PsneIF5A4 are excellent candidates for genetic engineering to improve salt and heavy metal tolerance in agricultural plants.

Association Analysis of the Growth of Black Poplar (Populus Nigra L.) Under Contrasting Nitrogen Levels

The European black poplar(Populus nigra L.)has been used as a germplasm resource for the breeding of new poplar varieties around the world.The identification and screening of its high nitrogen use efficiency genotypes could enable the breeding of new resource-efficient poplar varieties.The accessions were screened using MALDI-TOF MS genotyping technology for ammonium transporter(AMT)and nitrate transporters(NRT)genes against phenotypic data for seedling height and ground diameter traits,in both low and high nitrogen environments.Allele re-sequencing of seven genes related to root development was carried out using the minisequencing method.By cluster analysis,101 accessions of black poplar were divided into 4 populations,and it was concluded that Central Europe is the origin of the evolution of low-nitrogen and high-efficiency populations of European black poplar.Association study between SNP typing and seedling height and ground diameter traits showed that there were significant correlations between four SNP loci and growth traits under the contrasting N levels.We found that SNP3 and SNP4 in the PttAMT1;3 gene were significantly associated with seedling height traits,and that SNP2 and SNP7 in the PttAMT1;2 and PttAMT1;5 genes,respectively,were significantly associated with ground diameter traits.Thus,considerable allelic diversity is present within the candidate genes studied and can be utilized to develop functional markers to select for poplars with improved growth under N stress conditions.

No consistent daily variation in DNA methylation detected in Populus nigra leaves by methylation-sensitive amplification polymorphism analysis

DNA methylation, an epigenetic mechanism used by cells to control gene expression, has an important biological role in plant development and environmental fitness. Since plant DNA methylation is closely related to environmental conditions, variation during the day is expected. Here, in genetically identical plants of Populus nigra clone N46, DNA methylation changes in leaves over a 24 h period were detected using the methylation-sensitive amplification polymorphism method. The results showed different DNA methylation patterns in mature poplar leaves: not only in individuals at the same time, but also in samples at each of the six time during the day. In addition, night samples had a higher percentage of methylation than in morning samples. However, no statistically significant differences were found among the samples gathered at different times. Similar results were obtained for three other P. nigra clones with different genetic backgrounds. Real time qPCR showed that the DNA methyltransferase genes Pt-MET1 and Pt-SOM1 involved in CG DNA methylation in poplar were stable over a 24 h period in leaves of P. nigra N46 compared with circadian-controlled genes. That could be part of the reason that methylation of CCGG sites is stable in those leaves. That DNA methylation differed even in genetically identical plants indicates the specificity of DNA methylation changes in their genomes. No statistically significant differences in methylation changes were found between day and night, suggesting that DNA methylation is more stable than expected and is unlikely to be involved in circadian regulation in plants.

The effect of number of joints on bending properties of laminated lumber made from poplar (Populus nigra)

Connection plays an important role in structural components and end jointing is one of the most common connections in structural applications. This study was designed to investigate some mechanical properties （MOE and MOR） of solid wood samples manufactured from poplar （Populus nigra）, joined together through end jointing. As well, we studied combinations of lumber manufactured from 10-mm veneer, using a polyvinyl acetate adhesive. The results show that non-jointed lumber （control samples） have better bending properties （MOE and MOR） than jointed specimens and lumber made from laminated layers. On the whole, side-by- side joints have a negative effect on the MOR and MOE of laminated products, which is more pronounced in the MOR. By increasing the number of joints, the properties of combination of three-ply, i.e., bending strength and modulus of elasticity, decreased.

金叶杨不定芽诱导及增殖培养

本研究以金叶杨的叶片作为试验材料,对其不定芽诱导及增殖培养进行了研究。比较在不同消毒时间、基本培养基、激素配比的条件下,不定芽诱导及其增殖情况。结果表明:使用2%NaClO最佳消毒时间为9 min;金叶杨叶片诱导不定芽的最佳培养基为MS+6-BA 1.0 mg/L+IBA 0.3 mg/L,不定芽诱导率达到95.5%;金叶杨不定芽增殖的最佳培养基为6-BA 1.0 mg/L+IBA 0.4 mg/L+GA30.2 mg/L,不定芽增殖系数达到4.53。本研究成功建立了金叶杨不定芽诱导及增殖培养体系,为其快速繁殖提供理论基础。