Vol 63, No 3 (2016)

Using mutant plants of Arabidopsis thaliana, participation of the genes involved in abscisic acid (ABA) and cytokinins (CKs) metabolism and signaling in plant defense responses to heat shock (HS) was investigated. The magnitude of the stress action was assessed with biochemical indicators, such as accumulation of proline and malonic dialdehyde (MDA) and changes in the content of gene transcripts of heat shock proteins (HSPs) (HSP90.1 and HSP90.5) and transcription factor of HS (HSFA2) as well as stress-inducible genes, markers of oxidative stress (AOX1a, RD29, PRODH1, and P5CS1). Mutants with inactivated genes of ABA synthesis and, especially, signal perception exhibited lower thermo-resistance and accumulated elevated amounts of CK metabolism and signal transduction genes. In contrast, plants with inactivated components of CK synthesis and signal perception displayed increased tolerance to high temperatures and reduced levels of mRNA of oxidative stress genes as compared to wild type (WT) plants. However, enhancement of HS contributed to decrease of thermo-resistance of CKs receptor mutants up to the level of WT plants. Under hyperthermia, the stimulation of the plant defense mechanisms was accompanied by downregulation of the expression of CK metabolism and signal transduction genes (IPT3, CKX1, ARR5, AHK2, and AHK4) and ABA catabolism gene (CYP707A1) and upregulation of the expression of ABA synthesis and signal perception genes (ABA3 and ABI2). In the mutants insensitive to ABA, CYP707A1 gene was upregulated under the HS, while the expression of CK receptor gene expression did not reliably change. The results indicate that the response of the plants to elevated temperatures was determined not only by strength and the duration of the stress but the state of their ABA and CK metabolic and signaling systems as well.

The influence of cold hardening of rye (Secale cereale L.) and wheat (Triticum aestivum L.) seedlings on their resistance to the oxidative stress (OS) agents, namely, 50 mM hydrogen peroxide or 5 mM iron (II) sulfate was studied. Unhardened rye seedlings were more resistant to hydrogen peroxide than those of wheat, since their growth was less inhibited, and they accumulated lesser amounts of lipid peroxidation products after a treatment with H₂O₂. The interspecific differences in responses to FeSO₄ were less significant. The unhardened seedlings of rye, in comparison with those of wheat, possessed more active guaiacol peroxidase (GPO) and more levels of anthocyanins and proline. In response to the OS agents, the unhardened rye seedlings enhanced activities of superoxide dismutase and catalase, whereas the wheat seedlings enhanced GPO activity and proline content. The cold hardening (6 days at 2°C) increased activities of antioxidant (AO) enzymes, contents of proline, sugars, and anthocyanins in seedlings of both species, and made the seedlings more resistant to the OS agents. After the cold hardening, rye seedlings were more resistant to OS than wheat seedlings. The hardened seedlings of both species activated the AO enzymes in response to H₂O₂ or FeSO₄ greater than the unhardened ones. However, the hardened wheat seedlings, in contrast to the unhardened ones, did not augment the proline content in contact with the OS agents. The conclusion was drawn on different contributions of AO enzymes and low-molecular weight compounds to the basal and induced by the cold—hardening resistances of rye and wheat seedlings to OS.

The effects of low and moderate salinity (100 and 200 mM NaCl, respectively) and iso-osmotic stress generated by polyethylene glycol PEG (1) (–0.3 MPa) and PEG (2) (–0.6 MPa) on maximum quantum yield of photosystem II (PSII), growth, photosynthesis, transpiration, dark respiration, water use efficiency (WUE), water content, chlorophyll, proline, Na⁺ and K⁺ concentrations were investigated in shoots of two ecotypes С₃–С₄ xero-halophyte Bassia sedoides (Pall.) Aschers. Plants were grown from seeds of two Southern Urals populations (Makan and Podolsk) differing in their bioproductivity. Aboveground biomass of the Makan plants was approximately 10-fold higher than that of the Podolsk ecotype. The plants of both ecotypes were sensitive to water deficit. They showed similar decrease in biomass, water content, net photosynthesis and transpiration intensity under both low and moderate osmotic stress (PEG). However, the content of сhlorophyll and free proline in shoots of the Podolsk plants increased under moderate osmotic stress (PEG(2)). Under salinity the differences between transpiration, F_v/F_m, WUE, water content, chlorophyll and proline concentrations in shoots of two ecotypes were no found. But, the Podolsk plants showed decrease in the growth parameters (1.5-fold), increase in the dark respiration intensity (2-fold) and the Na⁺/K⁺ ratio (1.2-fold) under moderate salinity (200 mM NaCl). Thus, the reduction of bioproductivity of the Podolsk ecotype under salinity was the result of ionic rather than osmotic factor of salinity. In the Podolsk plants the additional transpiration costs and consumption of assimilates (correspondingly) increased with the toxic sodium ion accumulation under salinity. This led to decrease in the growth parameters. Thus, two B. sedoides ecotypes have different adaptive strategies of tolerance to the ionic factor of salt stress at the level of the physiological processes associated with the dark CO₂ gas exchange. Moreover, in less tolerant and productive Podolsk ecotype the increase in proline content in shoots characterized comparatively low adaptation to osmotic factor, and the increase in dark respiration and the Na⁺/K⁺ ratio pointed to relatively low resistance to ion factor of salinity as compared with the Makan ecotype.

Nitrogen (N) is an essential macronutrient for plant growth and development. Insufficient supply of N leads to extensive physiological and biochemical changes in plant. However, the molecular mechanisms of response to N are still unknown. In this study, global transcriptome profiles of wheat (Triticum aestivum L.) leaf and root under limited and sufficient N conditions were generated using Illumina RNA-sequencing. Then SeqPrep and Sickle were used to filter the raw reads and genes were assembled and predicted using Trinity. The Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) for wheat transcripts were obtained from GO and KEGG databases, respectively. Clusters of orthologous group terms were obtained using Blastx 2.2.24+ in STRING 9.0. Differentially expressed genes (DEGs) were then screened using edgeR software with false discovery rate <0.05 and |log₂FC| ≥ 1, followed by the protein–protein interaction (PPI) network construction for DEGs using Cytoscape. As a result, 126956 transcripts were obtained. Among them, 47590 transcripts were categorized into 56 GO terms, such as metabolic process; 25607 transcripts were assigned to 42 KEGG pathways, such as metabolic pathways; and 27194 unique sequences were classified into 25 COG categories, such as transcription. Moreover, 1267 (179 up-regulated and 1088 down-regulated) and 1996 DEGs (868 up-regulated and 1128 down-regulated) were obtained in leaf and root, respectively. In the PPI networks, BRADI1G77050.1, BRADI2G40600.1 and rpl2 were found to be the hub nodes. Thus, these screened DEGs might be associated with N metabolism and stress response in wheat, especially BRADI1G77050.1, BRADI2G40600.1 and rpl2.

Cyclization of 2,3-oxidosqualene by different oxidosqualene cyclase (OSC) genes is responsible for sapogenin heterogeneity. The very first phase is the conversion of 2,3-oxidosqualene into β-amyrin by β-amyrin synthase (BAS) gene, a member of OSC family, in soy saponin biosynthesis pathway. This paper reports the identification of a new BAS gene (GmBAS3) and its expression pattern in soybean (Glycine max (L.) Merr.). GmBAS3 gene was identified by PCR/RACE method with an open reading frame of 2286 bp nucleotides encoding a 762 amino acid long protein devouring a characteristic QW motif repeated five times and DCTAE motif. GmBAS3 shared 96 and 92% homology with Glycyrrhiza uralensis BAS and Lotus japonicus putative BAS respectively. Expression of the gene was detected by RT-PCR in regard to seedlings age and tissue type. A spatio-temporal expression of GmBAS3 was found in 21-day-old seedlings in the hypocotyls, young leaves and mature leaves but not observed in stem and root tissues. No expression was perceived in 10-day-old seedling. This study also support the premise that β-amyrin synthesis hang on more than one type of BAS genes with there expression in different plant parts at different times.

Alkaligrass (Puccinellia chinampoensis Ohwi), one of the important forage grasses in saline-alkalieroded grasslands, has been proved to be invaluable for improving saline-alkali soils. However, little is known of its genetic instabilities during in vitro culture for its artificial breeding. In this paper, a simple and efficient regeneration system of mature seed-induced calli in alkaligrass was established, and the somaclonal variation in the regenerated plants was assessed by inter-simple sequence repeat (ISSR) and retrotransposon-microsatellite amplified polymorphism (REMAP) markers. 18 randomly chosen regenerants were subjected to ISSR and REMAP analysis with the shoot from the same grain of seed as the control. ISSR analysis showed that of the 145 scored bands, 13 were polymorphic among the analyzed samples, giving rise to a genetic variation frequency of 8.97%. REMAP analysis revealed that 4 out of 127 scored bands were polymorphic, a genetic variation frequency of 3.15% occurred. Cluster analysis indicated that the genetic similarity index calculated on the basis of ISSR data or REMAP data among the 18 regenerated plants and the donor plant was 0.974 and 0.996 respectively. All the results confirmed that somaclonal variation was induced by tissue culture in alkaligrass at a higher frequency, and indicated that the regeneration system could be a viable option for genetic improvement of alkaligrass by biotechniques.

Reference genes are frequently used as a normalization standard to obtain reliable data during quantitative real-time polymerase chain reaction (qRT-PCR). However, recent studies showed that most traditional reference genes were not stable under different treatments or environmental stresses, which may lead to misinterpret expression of the target genes. In this study, 7 candidate reference genes in tea plant (Camellia sinensis (L.) Kuntze cv. Yingshuang) were selected and their expression stability under different abiotic stresses was analyzed using geNorm, NormFinder, and BestKeeper methods. Our results suggest that TUA1 (alpha-1 tubulin) has the most stable expression under damage stresses according to 3 methods of analysis. For drought stresses, 18S rRNA, and GAPDH (glyceraldehyde-3-phosphate dehydrogenase) were the most stable genes. For cold, Al, and NaCl stresses, GAPDH and TUA1 may be the alternative options. Our results may provide an insight for identification of the optimal reference genes for tea plants under various treatments.