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Marked increases were found in the content of total soluble sugars, reducing sugars and ATP in winter wheat (Triticum aestivum L. cv. Frederick) during cold hardening. The changes in soluble sugars and ATP of spring wheat (T. aestivum L. cv. Glenlea) grown. under similar conditions were less pronounced. The increase in ATP content during hardening of winter wheat was not associated with significant changes in the content of ADP or AMP. The adenylate energy charge did not change during hardening in either cultivar, but it was higher in the winter cultivar under both growth conditions. This difference could be related to the cold hardiness capacity of winter wheat. [ABSTRACT FROM AUTHOR]

Winter, as compared with spring cereals, possess better acclimation mechanisms that allow them to overwinter and survive freezing temperatures. This difference is genetically programmed and involves a complex genetic system. To understand the nature of this system and its regulation by low temperature, genes associated with freezing tolerance in wheat (Triticum aestivum L.) were identified and characterized. Among these, the wcs120 gene family encodes a group of proteins ranging in size from 12 to 200 Wa. As shown by biochemical, immunohistochemical, molecular and genetic analyses, this gene family is specific to the Poaceae, highly abundant and coordinately regulated by low temperature. Furthermore, accumulation of WCS protein is directly correlated with the development of freezing tolerance. These analyses also revealed a regulatory control of the vernalization process over low temperature gene expression in winter cereals. Recent studies suggest that the molecular mechanisms controlling the expression of these genes involve negative regulatory factors that are modulated by phosphorylation. [ABSTRACT FROM AUTHOR]

Efficient procedures are described for high-yield isolation of mesophyll protoplasts from spring wheat (Triticum aestivum L. cv. Glenlea), winter wheat (Triticum aestivum L. cv. Frederick), barley (Hordeum vulgare L. cv. Bruce) and rye (Secale cereale L. cv. Puma). Factors such as plant age, composition of the incubation medium during isolation, purification procedures and culture medium affect protoplast yield, viability and metabolic competence, as measured by light-dependent CO2 fixation. Optimal osmolarity of the isolation medium was equivalent to 1.8 times that measured in the leaves of all plant material used. The presence of 2 mM ascorbic acid in the preincubation and isolation medium increased the yield by 50% and conserved viability and metabolic competence. The protoplasts were stable for up to 48 h without loss of either viability or of original activity of CO2 fixation, which was in the order of 100 μmol CO2 (mg chl)-1 h-1. In our MC-56 liquid medium these protoplasts regenerated cell walls within 72 h and a few divided. [ABSTRACT FROM AUTHOR]

We assessed the effects of short-term elevated CO2 on the light-saturated rates of photosynthesis ( Asat) of spring ('SR4A', 'Katepwa') and winter ('Musketeer', 'Norstar') wheat ( Triticum aestivum L.) and rye ( Secale cereale L.) cultivars grown at ambient CO2 (380 µmol C·mol-1) at either 20/16 °C (nonacclimated, NA) or 5/5 °C (cold acclimated, CA). In spring wheat-rye, cold acclimation decreased CO2-stimulation of Asat by 45%-60% relative to NA controls following a short-term (80 h) shift of plants from ambient to elevated CO2 (700 µmol C·mol-1). In contrast, in winter wheat-rye, cold acclimation enhanced CO2-stimulation of Asat by 15%-35% relative to NA controls upon a shift to elevated CO2. The stimulation observed for CA spring cultivars was about 60% less than that of CA winter cultivars. We conclude that a short-term exposure of spring cultivars to elevated CO2 cannot compensate for the cold acclimation-induced inhibition of Asat. Cold acclimation of spring cultivars appeared to exacerbate Rubisco CO2 substrate limitations present under ambient CO2. Furthermore, CA spring cultivars were unable to adjust their short-term temperature sensitivity of Asat under elevated CO2 compared with the winter cultivars. [ABSTRACT FROM AUTHOR]

Examines the expression profiling and bioinformatic analyses of a novel stress-regulated multispanning transmembrane protein family from cereals and arabidopsis. Presence of a highly conserved phosphorylation site; Development of freezing tolerance in cereals and Arabidopsis; Lack of homologous sequence found.

Cold acclimation and winter survival in cereal species is determined by complicated environmentally regulated gene expression. However, studies investigating these complex cold responses are mostly conducted in controlled environments that only consider the responses to single environmental variables. In this study, we have comprehensively profiled global transcriptional responses in crowns of field-grown spring and winter wheat (Triticum aestivum) genotypes and their near-isogenic lines with the VRN-A1 alleles swapped. This in-depth analysis revealed multiple signaling, interactive pathways that influence cold tolerance and phenological development to optimize plant growth and development in preparation for a wide range of over-winter stresses. Investigation of genetic differences at the VRN-A1 locus revealed that a vernalization requirement maintained a higher level of cold response pathways while VRN-A1 genetically promoted floral development. Our results also demonstrated the influence of genetic background on the expression of cold and flowering pathways. The link between delayed shoot apex development and the induction of cold tolerance was reflected by the gradual up-regulation of abscisic acid-dependent and C-REPEAT-BINDING FACTOR pathways. This was accompanied by the down-regulation of key genes involved in meristem development as the autumn progressed. The chromosome location of differentially expressed genes between the winter and spring wheat genetic backgrounds showed a striking pattern of biased gene expression on chromosomes 6A and 6D, indicating a transcriptional regulation at the genome level. This finding adds to the complexity of the genetic cascades and gene interactions that determine the evolutionary patterns of both phenological development and cold tolerance traits in wheat. [ABSTRACT FROM AUTHOR]

Background: Wheat is a major staple crop with broad adaptability to a wide range of environmental conditions. This adaptability involves several stress and developmentally responsive genes, in which microRNAs (miRNAs) have emerged as important regulatory factors. However, the currently used approaches to identify miRNAs in this polyploid complex system focus on conserved and highly expressed miRNAs avoiding regularly those that are often lineage-specific, condition-specific, or appeared recently in evolution. In addition, many environmental and biological factors affecting miRNA expression were not yet considered, resulting still in an incomplete repertoire of wheat miRNAs. Results: We developed a conservation-independent technique based on an integrative approach that combines machine learning, bioinformatic tools, biological insights of known miRNA expression profiles and universal criteria of plant miRNAs to identify miRNAs with more confidence. The developed pipeline can potentially identify novel wheat miRNAs that share features common to several species or that are species specific or clade specific. It allowed the discovery of 199 miRNA candidates associated with different abiotic stresses and development stages. We also highlight from the raw data 267 miRNAs conserved with 43 miRBase families. The predicted miRNAs are highly associated with abiotic stress responses, tolerance and development. GO enrichment analysis showed that they may play biological and physiological roles associated with cold, salt and aluminum (Al) through auxin signaling pathways, regulation of gene expression, ubiquitination, transport, carbohydrates, gibberellins, lipid, glutathione and secondary metabolism, photosynthesis, as well as floral transition and flowering. Conclusion: This approach provides a broad repertoire of hexaploid wheat miRNAs associated with abiotic stress responses, tolerance and development. These valuable resources of expressed wheat miRNAs will help in elucidating the regulatory mechanisms involved in freezing and Al responses and tolerance mechanisms as well as for development and flowering. In the long term, it may help in breeding stress tolerant plants. [ABSTRACT FROM AUTHOR]

Background: Wheat is a major staple crop with broad adaptability to a wide range of environmental conditions. This adaptability involves several stress and developmentally responsive genes, in which microRNAs (miRNAs) have emerged as important regulatory factors. However, the currently used approaches to identify miRNAs in this polyploid complex system focus on conserved and highly expressed miRNAs avoiding regularly those that are often lineage-specific, condition-specific, or appeared recently in evolution. In addition, many environmental and biological factors affecting miRNA expression were not yet considered, resulting still in an incomplete repertoire of wheat miRNAs. Results: We developed a conservation-independent technique based on an integrative approach that combines machine learning, bioinformatic tools, biological insights of known miRNA expression profiles and universal criteria of plant miRNAs to identify miRNAs with more confidence. The developed pipeline can potentially identify novel wheat miRNAs that share features common to several species or that are species specific or clade specific. It allowed the discovery of 199 miRNA candidates associated with different abiotic stresses and development stages. We also highlight from the raw data 267 miRNAs conserved with 43 miRBase families. The predicted miRNAs are highly associated with abiotic stress responses, tolerance and development. GO enrichment analysis showed that they may play biological and physiological roles associated with cold, salt and aluminum (Al) through auxin signaling pathways, regulation of gene expression, ubiquitination, transport, carbohydrates, gibberellins, lipid, glutathione and secondary metabolism, photosynthesis, as well as floral transition and flowering. Conclusion: This approach provides a broad repertoire of hexaploid wheat miRNAs associated with abiotic stress responses, tolerance and development. These valuable resources of expressed wheat miRNAs will help in elucidating the regulatory mechanisms involved in freezing and Al responses and tolerance mechanisms as well as for development and flowering. In the long term, it may help in breeding stress tolerant plants. [ABSTRACT FROM AUTHOR]

The einkorn wheat mutant mvp-1 (maintained vegetative phase 1) has a non-flowering phenotype caused by deletions including, but not limited to, the genes CYS, PHYC, and VRN1. However, the impact of these deletions on global gene expression is still unknown. Transcriptome analysis showed that these deletions caused the upregulation of several pathogenesis-related (PR) and jasmonate-responsive genes. These results suggest that jasmonates may be involved in flowering and vernalization in wheat. To test this hypothesis, jasmonic acid (JA) and methyl jasmonate (MeJA) content in mvp and wild-type plants was measured. The content of JA was comparable in all plants, whereas the content of MeJA was higher by more than 6-fold in mvp plants. The accumulation of MeJA was also observed in vernalizationsensitive hexaploid winter wheat during cold exposure. This accumulation declined rapidly once plants were deacclimated under floral-inductive growth conditions. This suggests that MeJA may have a role in floral transition. To confirm this result, we treated vernalization-insensitive spring wheat with MeJA. The treatment delayed flowering with significant downregulation of both TaVRN1 and TaFT1 genes. These data suggest a role for MeJA in modulating vernalization and flowering time in wheat. [ABSTRACT FROM AUTHOR]

The einkorn wheat mutant mvp-1 (maintained vegetative phase 1) has a non-lowering phenotype caused by deletions including, but not limited to, the genes CYS, PHYC, and VRN1. However, the impact of these deletions on global gene expression is still unknown. Transcriptome analysis showed that these deletions caused the upregulation of several pathogenesis-related (PR) and jasmonate-responsive genes. These results suggest that jasmonates may be involved in lowering and vernalization in wheat. To test this hypothesis, jasmonic acid (JA) and methyl jasmonate (MeJA) content in mvp and wild-type plants was measured. The content of JA was comparable in all plants, whereas the content of MeJA was higher by more than 6-fold in mvp plants. The accumulation of MeJA was also observed in vernalization-sensitive hexaploid winter wheat during cold exposure. This accumulation declined rapidly once plants were deac-climated under floral-inductive growth conditions. This suggests that MeJA may have a role in floral transition. To confirm this result, we treated vernalization-insensitive spring wheat with MeJA. The treatment delayed lowering with significant downregulation of both TaVRN1 and TaFT1 genes. These data suggest a role for MeJA in modulating vernalization and lowering time in wheat. [ABSTRACT FROM AUTHOR]

This study compared the photosynthetic performance and the global gene expression of the winter hardy wheat Triticum aestivum cv Norstar grown under non-acclimated (NA) or cold-acclimated (CA) conditions at either ambient CO2 or elevated CO2. CA Norstar maintained comparable light-saturated and CO2-saturated rates of photosynthesis but lower quantum requirements for PSII and non-photochemical quenching relative to NA plants even at elevated CO2. Neither NA nor CA plants were sensitive to feedback inhibition of photosynthesis at elevated CO2. Global gene expression using microarray combined with bioinformatics analysis revealed that genes affected by elevated CO2 were three times higher in NA (1,022 genes) compared with CA (372 genes) Norstar. The most striking effect was the down-regulation of genes involved in the plant defense responses in NA Norstar. In contrast, cold acclimation reversed this down-regulation due to the cold induction of genes involved in plant pathogenesis resistance; and cellular and chloroplast protection. These results suggest that elevated CO2 has less impact on plant performance and productivity in cold-adapted winter hardy plants in the northern climates compared with warmer environments. Selection for cereal cultivars with constitutively higher expression of biotic stress defense genes may be necessary under elevated CO2 during the warm growth period and in warmer climates. [ABSTRACT FROM PUBLISHER]

Abstract: The flavone, tricin (5,7,4′-trihydroxy-3′,5′-dimethoxyflavone) has great potential as an anticancer agent, due to its specific chemopreventive activity. In spite of these characteristics, its use in preclinical studies is still limited, mainly because of its limited availability and high production cost. Tricin is found mainly in cereal grains, such as wheat, rice, barley, oat and maize. However, its concentration in these plants is not sufficient for commercial use. To find a reliable, rich source of tricin, we investigated its distribution in different parts of wheat (Triticum aestivum) and designed an efficient method for its isolation and purification. The highest amount (770±157mg/kg dry weight) was found in the husks of winter wheat. This concentration is one of the highest in any plant species and is considered as a cheap source of natural tricin. The purified wheat husks tricin was found to be a selective potent inhibitor of two cancer cell lines of liver and pancreas, while having no side effects on normal cells. This selective action suggests that tricin could be considered as a potential candidate for pre-clinical trials as a chemopreventive agent. In addition, fibre-rich crude wheat husk could be used as a natural chemopreventive agent in food supplement. [Copyright &y& Elsevier]

Abstract: Diabetes is a global epidemic that affects about 285million people worldwide. For severely-ill patients with type I diabetes, whole pancreas or islet transplantation is the only therapeutic option. Islet transplantation is hindered by the scarce supply of fresh functional islets and limitations in cryopreservation procedures. Thus, improved cryopreservation procedures are needed to increase the availability of functional islets for clinical applications. Towards this goal, this work developed a cryopreservation protocol for pancreatic cells using proteins that accumulate naturally in freezing-tolerant plants. A preincubation of cells with 1% lecithin-1% glycerol-1% N-methylpyrrolidone followed by cryopreservation with partially purified proteins from wheat improved the viability and insulin-secreting properties of INS832/13 cells, compared to cryopreservation with 10% dimethyl sulfoxide (Me2SO). The major factor that enhanced the cryoprotective effect of the wheat protein formulation was preincubation with the lipid lecithin. Expression profiles of genes involved in metabolic and signaling functions of pancreatic cells (Ins, Glut1/2/3, Pdx1, Reg1α) were similar between fresh cells and those cryopreserved with the plant protein formulation. This novel plant-based technology, which is non-toxic and contains no animal material, is a promising alternative to Me2SO for cryopreservation of insulin-secreting pancreatic cells. [Copyright &y& Elsevier]

Abstract: In plants, O-methylation is mediated by an enzyme family of O-methyltransferases (OMTs) that transfer the methyl groups from the methyl donor, S-adenosyl-L-methionine (AdoMet) to suitable phenolic acceptor molecules. In a previous study [1], a flavonoid OMT (TaOMT2) was isolated and characterized from wheat (Triticum aestivum L.) leaves. Its novel gene product catalyzes three sequential O-methylations of the flavone tricetin (5,7,3′,4′,5′-pentahydroxyflavone) to its 3′-monomethyl-(selgin)→3′,5′-dimethyl-(tricin)→3′,4′,5′-trimethyl (TMT) ether derivatives, with tricin being the major product of the reaction. In this report, the biological significance of tricetin methylation was investigated by measuring the OMT activity, its expression level, and the accumulation of its major product (tricin) at different stages of development of wheat plants exposed to different abiotic stresses such as cold, salt and drought. The results showed that tricin accumulates mostly in wheat inflorescences under normal conditions compared to leaves and other developmental stages. Tricin accumulation was associated with increased TaOMT2 expression level and its enzyme activity, suggesting a possible de novo synthesis of the enzyme at this important developmental stage. This phenomenon may be attributed to the putative role of tricin in protecting seeds against biotic and abiotic stresses. The functions of tricin during growth and development of wheat and the importance of tricetin methylation during abiotic stresses are discussed. [Copyright &y& Elsevier]

The transition to flowering in winter wheat requires prolonged exposure to low temperature, a process called vernalization. This process is regulated by a genetic pathway that involves at least three genes, Triticum aestivum VERNALIZATION 1 ( TaVRN1), Triticum aestivum VERNALIZATION 2 ( TaVRN2) and Triticum aestivum FLOWERING LOCUS T- like 1 ( TaFT1). These genes regulate flowering by integrating environmental and developmental cues. To determine whether the expression of these genes is associated with the chromatin methylation state during vernalization in wheat, the level of two markers of histone modifications, the activator histone H3 trimethylation of lysine 4 (H3K4me3) and the repressor histone H3 trimethylation of lysine 27 (H3K27me3) were measured at the promoter regions of these three genes. Bioinformatics analysis of these promoters demonstrates the presence of conserved cis-acting elements in the promoters of the three vernalization genes, TaVRN1, TaVRN2 and TaFT1. These elements are targeted by common transcription factors in the vernalization responsive cereals. These promoters also contain the functional 'units' PRE/TRE targeted by Polycomb and Trithorax proteins that maintain repressed or active transcription states of developmentally regulated genes. These proteins are known to be associated with the regulation of H3K4me3 and H3K27me3. Expression studies indicate that TaVRN1 and TaFT1 are up-regulated by vernalization in winter wheat. This up-regulation is associated with increased level of the activator H3K4me3 with no change in the level of the repressor H3K27me3 at the promoter region. This study shows that the flowering transition induced by vernalization in winter wheat is associated with histone methylation at the promoter level of TaVRN1 and TaFT1 while the role of these markers is less evident in TaVRN2 repression. This may represent part of the cellular memory of vernalization in wheat. [ABSTRACT FROM AUTHOR]

The contributions of phenotypic plasticity to photosynthetic performance in winter (cv Musketeer, cv Norstar) and spring (cv SR4A, cv Katepwa) rye (Secale cereale) and wheat (Triticum aestivum) cultivars grown at either 20°C [non-acclimated (NA)] or 5°C [cold acclimated (CA)] were assessed. The 22-40% increase in light-saturated rates of CO2 assimilation in CA vs NA winter cereals were accounted for by phenotypic plasticity as indicated by the dwarf phenotype and increased specific leaf weight. However, phenotypic plasticity could not account for (1) the differential temperature sensitivity of CO2 assimilation and photosynthetic electron transport, (2) the increased efficiency and light-saturated rates of photosynthetic electron transport or (3) the decreased light sensitivity of excitation pressure and non-photochemical quenching between NA and NA winter cultivars. Cold acclimation decreased photosynthetic performance of spring relative to winter cultivars. However, the differences in photosynthetic performances between CA winter and spring cultivars were dependent upon the basis on which photosynthetic performance was expressed. Overexpression of BNCBF17 in Brassica napus generally decreased the low temperature sensitivity (Q10) of CO2 assimilation and photosynthetic electron transport even though the latter had not been exposed to low temperature. Photosynthetic performance in wild type compared to the BNCBF17-overexpressing transgenic B. napus indicated that CBFs/DREBs regulate not only freezing tolerance but also govern plant architecture, leaf anatomy and photosynthetic performance. The apparent positive and negative effects of cold acclimation on photosynthetic performance are discussed in terms of the apparent costs and benefits of phenotypic plasticity, winter survival and reproductive fitness. [ABSTRACT FROM AUTHOR]

Abstract: A study of wheat (Triticum aestivum L.) leaves phenolome was carried out during cold acclimation of the winter (Claire) and spring (Bounty) varieties using a combination of HPLC–ESI–MS techniques. A total of 40 phenolic and flavonoid compounds were identified, and consisted mainly of two coumarin derivatives, eight simple phenolic derivatives, 10 hydroxycinnamoyl amides and 20 flavonoid derivatives. Identification and quantification of individual compounds were performed using an HPLC system coupled with a photodiode array detector and two different ESI–MS systems, in combination with a multiple reaction monitoring (MRM) technique. The analyses indicated that, although there were no qualitative differences in their profiles, the winter variety exhibited a higher phenolic content compared to the spring variety when both were grown under non-acclimated (control) conditions. Cold acclimation, on the other hand, resulted in a significant differential accumulation of phenolic compounds in both varieties: mostly as luteolin C-glycosides and their O-methyl derivatives in the winter variety (Claire) and a derivative of hydroxycinnamoyl amide in the spring variety (Bounty). These compounds accumulated in relatively large amounts in the apoplastic compartment. The accumulation of the O-methylated derivatives was associated with a marked increase in O-methyltransferase (OMT) activity. In addition, the trimethylated flavone, 3′,4′,5′-trimethyltricetin was identified for the first time in the native extracts of both control and cold-acclimated wheat leaves. The accumulation of a mixture of beneficial flavonoids, such as iso-orientin, vitexin and tricin in cold acclimated wheat leaves, attests for its potential as an inexpensive source of a health-promoting supplement to the human diet. [Copyright &y& Elsevier]

Abstract: The aim of this study was to produce adjuvant with high biosafety, efficacy and low cost. Towards this goal, the plant Nicotiana benthamiana transient expression system was successfully used to express Salmonella typhimurium''s flagellin (FljB). The yield of the expressed FljB was 280mg per kg of fresh weight (FW) leaves. The lyophilized plant powder containing plant expressing FljB was mixed with ovalbumin (OVA) and used for oral immunization of BALB/c mice. The ELISA analysis showed higher and accelerated OVA-specific serum antibody responses in mice given the mixture when compared to animals receiving OVA alone. Furthermore, FljB elicited a mixed Th1/Th2 response as shown by the presence of specific anti-OVA IgG1, IgG2a and IgG2b isotypes. OVA-specific IgAs were also detected in mice given the mixture. Cell-mediated immune response to OVA was induced by FljB as determined by a spleen lymphocyte specific proliferation test. No immune response was generated against FljB. In conclusion, our results showed for the first time the production of FljB in plants and the efficient use of the crude lyophilized extract as an adjuvant for oral immunization. [Copyright &y& Elsevier]

The vernalization gene 2 (VRN2), is a major flowering repressor in temperate cereals that is regulated by low temperature and photoperiod. Here we show that the gene from Triticum aestivum (TaVRN2) is also regulated by salt, heat shock, dehydration, wounding and abscissic acid. Promoter analysis indicates that TaVRN2 regulatory region possesses all the specific responsive elements to these stresses. This suggests pleiotropic effects of TaVRN2 in wheat development and adaptability to the environment. To test if TaVRN2 can act as a flowering repressor in species different from the temperate cereals, the gene was ectopically expressed in the model plant Arabidopsis. Transgenic plants showed no alteration in morphology, but their flowering time was significantly delayed compared to controls plants, indicating that TaVRN2, although having no ortholog in Brassicaceae, can act as a flowering repressor in these species. To identify the possible mechanism by which TaVRN2 gene delays flowering in Arabidopsis, the expression level of several genes involved in flowering time regulation was determined. The analysis indicates that the late flowering of the 35S::TaVRN2 plants was associated with a complex pattern of expression of the major flowering control genes, FCA, FLC, FT, FVE and SOC1. This suggests that heterologous expression of TaVRN2 in Arabidopsis can delay flowering by modulating several floral inductive pathways. Furthermore, transgenic plants showed higher freezing tolerance, likely due to the accumulation of CBF2, CBF3 and the COR genes. Overall, our data suggests that TaVRN2 gene could modulate a common regulator of the two interacting pathways that regulate flowering time and the induction of cold tolerance. The results also demonstrate that TaVRN2 could be used to manipulate flowering time and improve cold tolerance in other species. [ABSTRACT FROM AUTHOR]

Background: Lipocalins are a large and diverse family of small, mostly extracellular proteins implicated in many important functions. This family has been studied in bacteria, invertebrate and vertebrate animals but little is known about these proteins in plants. We recently reported the identification and molecular characterization of the first true lipocalins from plants, including the Apolipoprotein D ortholog AtTIL identified in the plant model Arabidopsis thaliana. This study aimed to determine its physiological role in planta. Results: Our results demonstrate that the AtTIL lipocalin is involved in modulating tolerance to oxidative stress. AtTIL knock-out plants are very sensitive to sudden drops in temperature and paraquat treatment, and dark-grown plants die shortly after transfer to light. These plants accumulate a high level of hydrogen peroxide and other ROS, which causes an oxidative stress that is associated with a reduction in hypocotyl growth and sensitivity to light. Complementation of the knock-out plants with the AtTIL cDNA restores the normal phenotype. On the other hand, overexpression enhances tolerance to stress caused by freezing, paraquat and light. Moreover, this overexpression delays flowering and maintains leaf greenness. Microarray analyses identified several differentially-regulated genes encoding components of oxidative stress and energy balance. Conclusion: This study provides the first functional evidence that a plant lipocalin is involved in modulating tolerance to oxidative stress. These findings are in agreement with recently published data showing that overexpression of ApoD enhances tolerance to oxidative stress and increases life span in mice and Drosophila. Together, the three papers strongly support a similar function of lipocalins in these evolutionary-distant species. [ABSTRACT FROM AUTHOR]

In wheat, VRN1/TaVRN1 and VRN2/TaVRN2 determine the growth habit and flowering time. In addition, the MADS box transcription factor VEGETATIVE TO REPRODUCTIVE TRANSITION 2 (TaVRT2) is also associated with the vernalization response in a manner similar to TaVRN2. However, the molecular relationship between these three genes and their products is unknown. Using transient expression assays in Nicotiana benthamiana, we show that TaVRT2 acts as a repressor of TaVRN1 transcription. TaVRT2 binds the CArG motif in the TaVRN1 promoter and represses its activity in vivo. In contrast, TaVRN2 does not bind the TaVRN1 promoter and has no direct effect on its activity, but it can enhance the repression effect of TaVRT2. This suggests that a repressor complex regulates the expression of TaVRN1. In winter wheat, TaVRT2, TaVRN2 and TaVRN1 transcripts accumulate in the shoot apical meristem and young leaves, and temporal expression is consistent with TaVRT2 and TaVRN2 being repressors of floral transition, whereas TaVRN1 is an activator. Non-vernalized spring wheat grown under a short-day photoperiod accumulates TaVRT2 and shows a delay in flowering, suggesting that TaVRT2 is regulated independently by photoperiod and low temperature. The data presented suggest that TaVRT2, in association with TaVRN2, represses the transcription of TaVRN1. [ABSTRACT FROM AUTHOR]

In plants and algal cells, changes in light intensity can induce intrachloroplastic and retrograde regulation of gene expression in response to changes in the plastoquinone redox status. We review the evidence in support of the thesis that the chloroplast acts as a general sensor of cellular energy imbalance sensed through the plastoquinone pool. Alteration in cellular energy balance caused by chloroplast or mitochondrial metabolism can induce intracellular signalling to affect chloroplastic and nuclear gene expression in response, not only to light intensity, but to a myriad of abiotic stresses. In addition, this chloroplastic redox sensing also appears to have a broader impact, affecting long-distance systemic signalling related to plant growth and development. The organization of the respiratory electron transport chains of mitochondria and heterotrophic prokaryotes is comparable to that of chloroplast thylakoid membranes, and the redox state of the respiratory ubiquinone pool is a well-documented cellular energy sensor. Thus, modulation of electron transport component redox status by abiotic stress regulates organellar as well as nuclear gene expression. From the evidence presented, we suggest that the photosynthetic and respiratory machinery in prokaryotic and eukaryotic organisms have a dual function: primary cellular energy transformation, and global environmental sensing. [ABSTRACT FROM AUTHOR]

Lipocalins are a group of proteins that have been characterized in bacteria, invertebrate, and vertebrate animals. However, very little is known about plant lipocalins. We have previously reported the cloning of the first true plant lipocalins. Here we report the identification and characterization of plant lipocalins and lipocalin-like proteins using an integrated approach of data mining, expression studies, cellular localization, and phylogenetic analyses. Plant lipocalins can be classified into two groups, temperature- induced lipocalins (TILs) and chloroplastic lipocalins (CHLs). In addition, violaxanthin de-epoxidases (VDEs) and zeaxanthin epoxidases (ZEPs) can be classified as lipocalin-like proteins. CHLs, VDEs, and ZEPs possess transit peptides that target them to the chloroplast. On the other hand, TILs do not show any targeting peptide, but localization studies revealed that the proteins are found at the plasma membrane. Expression analyses by quantitative real-time PCR showed that expression of the wheat (Triticum aestivum) lipocalins and lipocalin-like proteins is associated with abiotic stress response and is correlated with the plant's capacity to develop freezing tolerance. In support of this correlation, data mining revealed that lipocalins are present in the desiccation-tolerant red algae Porphyra yezoensis and the cryotolerant marine yeast Debaryomyces hansenii, suggesting a possible association with stress-tolerant organisms. Considering the plant lipocalin properties, tissue specificity, response to temperature stress, and their association with chloroplasts and plasma membranes of green leaves, we hypothesize a protective function of the photosynthetic system against temperature stress. Phylogenetic analyses suggest that TIL lipocalin members in higher plants were probably inherited from a bacterial gene present in a primitive unicellular eukaryote. On the other hand, CHLs, VDEs, and ZEPs may have evolved from a cyanobacterial ancestral gene after the formation of the cyanobacterial endosymbiont from which the chloroplast originated. [ABSTRACT FROM AUTHOR]

Freezing tolerance in plants is a complex trait that occurs in many plant species during growth at low, nonfreezing temperatures, a process known as cold acclimation. This process is regulated by a multigenic system expressing broad variation in the degree of freezing tolerance among wheat cultivars. Microarray analysis is a powerful and rapid approach to gene discovery. In species such as wheat, for which large scale mutant screening and transgenic studies are not currently practical, genotype comparison by this methodology represents an essential approach to identifying key genes in the acquisition of freezing tolerance. A microarray was constructed with PCR amplified cDNA inserts from 1184 wheat expressed sequence tags (ESTs) that represent 947 genes. Gene expression during cold acclimation was compared in 2 cultivars with marked differences in freezing tolerance. Transcript levels of more than 300 genes were altered by cold. Among these, 65 genes were regulated differently between the 2 cultivars for at least 1 time point. These include genes that encode potential regulatory proteins and proteins that act in plant metabolism, including protein kinases, putative transcription factors, Ca2+ binding proteins, a Golgi localized protein, an inorganic pyrophosphatase, a cell wall associated hydrolase, and proteins involved in photosynthesis. [ABSTRACT FROM AUTHOR]

The initiation of the reproductive phase in winter cereals is delayed during winter until favorable growth conditions resume in the spring. This delay is modulated by low temperature through the process of vernalization. The molecular and genetic bases of the interaction between environmental factors and the floral transition in these species are still unknown. However, the recent identification of the wheat (Triticum aestivum L.) TaVRT-1 gene provides an opportunity to decipher the molecular basis of the flowering-time regulation in cereals. Here, we describe the characterization of another gene, named TaVRT-2, possibly involved in the flowering pathway in wheat. Molecular and phylogenetic analyses indicate that the gene encodes a member of the MADS-box transcription factor family that belongs to a clade responsible for flowering repression in several species. Expression profiling of TaVRT-2 in near-isogenic lines and different genotypes with natural variation in their response to vernalization and photoperiod showed a strong relationship with floral transition. Its expression is up-regulated in the winter genotypes during the vegetative phase and in photoperiod-sensitive genotypes during short days, and is repressed by vernalization to a level that allows the transition to the reproductive phase. Protein-protein interaction studies revealed that TaVRT-2 interacts with proteins encoded by two important vernalization genes (TaVRT-1/VRN-1 and VRN-2) in wheat. These results support the hypothesis that TaVRT-2 is a putative repressor of the floral transition in wheat. [ABSTRACT FROM AUTHOR]

To understand the molecular basis of freezing tolerance in plants, several low temperature-responsive genes have been identified from wheat. Among these are two genes named TaIRI-1 and TaIRI-2 (Triticumaestivum ice recrystallization inhibition) that are up-regulated during cold acclimation in freezing-tolerant species. Phytohormones involved in pathogen defense pathways (jasmonic acid and ethylene) induce the expression of one of the two genes. The encoded proteins are novel in that they have a bipartite structure that has never been reported for antifreeze proteins. Their N-terminal part shows similarity with the leucine-rich repeat-containing regions present in the receptor domain of receptor-like protein kinases, and their C-terminus is homologous to the ice-binding domain of some antifreeze proteins. The recombinant TaIRI-1 protein inhibits the growth of ice crystals, confirming its function as an ice recrystallization inhibition protein. The TaIRI genes were found only in the species belonging to the Pooideae subfamily of cereals. Comparative genomic analysis suggested that molecular evolutionary events took place in the genome of freezing-tolerant cereals to give rise to these genes with putative novel functions. These apparent adaptive DNA rearrangement events could be part of the molecular mechanisms that ensure the survival of hardy cereals in the harsh freezing environments. [ABSTRACT FROM AUTHOR]

Progress in freezing tolerance (FT) improvement through plant breeding approaches has met with little success in the last 50 years. Engineering plants for greater FT through plant transformation is one possible way to reduce the damage caused by freezing. Here, we report an improvement of the selection procedure and the transfer of the wheat Wcor410a acidic dehydrin gene in strawberry. The encoded protein has previously been shown to be associated with the plasma membrane, and its level of accumulation has been correlated with the degree of FT in different wheat genotypes. The WCOR410 protein was expressed in transgenic strawberry at a level comparable with that in cold-acclimated wheat. Freezing tests showed that cold-acclimated transgenic strawberry leaves had a 5 °C improvement of FT over wild-type or transformed leaves not expressing the WCOR410 protein. However, no difference in FT was found between the different plants under non-acclimated conditions, suggesting that the WCOR410 protein needs to be activated by another factor induced during cold acclimation. These data demonstrate that the WCOR410 protein prevents membrane injury and greatly improves FT in leaves of transgenic strawberry. A better understanding of the limiting factors allowing its activation may open up the way for engineering FT in different plant organs, and may find applications for the cryopreservation of human tissues and organs. [ABSTRACT FROM AUTHOR]

The molecular genetics of vernalization, defined as the promotion of flowering by cold treatment, is still poorly understood in cereals. To better understand this mechanism, we cloned and characterized a gene that we named TaVRT-1 (wheat [Triticum aestivum] vegetative to reproductive transition-1). Molecular and sequence analyses indicated that this gene encodes a protein homologous to the MADS-box family of transcription factors that comprises certain flowering control proteins in Arabidopsis. Mapping studies have localized this gene to the Vrn-1 regions on the long arms of homeologous group 5 chromosomes, regions that are associated with vernalization and freezing tolerance (FT) in wheat. The level of expression of TaVRT-1 is positively associated with the vernalization response and transition from vegetative to reproductive phase and is negatively associated with the accumulation of COR genes and degree of FT. Comparisons among different wheat genotypes, near-isogenic lines, and cereal species, which differ in their vernalization response and FT, indicated that the gene is inducible only in those species that require vernalization, whereas it is constitutively expressed in spring habit genotypes. In addition, experiments using both the photoperiod-sensitive barley (Hordeum vulgare cv Dicktoo) and short or long day de-acclimated wheat revealed that the expression of TaVRT-1 is also regulated by photoperiod. These expression studies indicate that photoperiod and vernalization may regulate this gene through separate pathways. We suggest that TaVRT-1 is a key developmental gene in the regulatory pathway that controls the transition from the vegetative to reproductive phase in cereals. [ABSTRACT FROM AUTHOR]

Focuses on the molecular and biochemical characterization of a gene encoding a novel O-methyltransferase that catalyzes the methylation of 7,8-dihydroxycoumarin, daphnetin. Methylation of position 8 of daphnetin; Role in modulating cold acclimation and photosystem II excitation pressure.

Two cDNAs corresponding to a novel lipocalin were identified from wheat and Arabidopsis. The two cDNAs designated Tatil for Triticum aestivum L. temperature-induced lipocalin and Attil for Arabidopsis thaliana temperature-induced lipocalin encode polypeptides of 190 and 186 amino acids respectively. Structure analyses indicated the presence of the three structurally conserved regions that characterize lipocalins. Sequence analyses revealed that this novel class of plant lipocalin shares homology with three evolutionarily related lipocalins: the mammalian apolipoprotein D (ApoD), the bacterial lipocalin and the insect Lazarillo. The comparison of the putative tertiary structures of both the human ApoD and the wheat TaTIL suggest that the two proteins differ in membrane attachment and ligand interaction. Northern analyses demonstrated that Tatil and Attil transcripts are upregulated during cold acclimation and heat-shock treatment. The putative functions of this novel class of plant lipocalins during temperature stresses are discussed. [Copyright &y& Elsevier]

Four immunologically related proteins that belong to the annexin family were identified in cold acclimated wheat (Triticum aestivum). Two soluble forms with molecular masses of 34 and 36 kDa were found to bind phospholipid membranes in a calcium-dependent manner. These two forms are similar to the previously reported doublet in several plant species. The other two forms, with molecular masses of 39 and 22.5 kDa, were found associated with the microsomal fraction. Biochemical analysis showed that both forms are intrinsic membrane proteins and their association with the membrane is calcium independent. This is, to our knowledge, the first report of the presence of these annexin forms in plants. Membrane purification by two phase partitioning demonstrated that the p39 form is localized to the plasma membrane. Immunoblot analysis showed that the protein level of both p39 and p22.5 increases gradually reaching a maximum level after one day of low temperature exposure. The protein accumulation was similar in both hardy and less hardy cultivars, suggesting that the accumulation is not correlated with freezing tolerance. The results are discussed with respect to the possible role of these new intrinsic membrane annexins in low temperature signal transduction pathway. [ABSTRACT FROM AUTHOR]

The accumulation of the osmolyte betaine was found to be correlated with the development of freezing tolerance (FT) of two wheat cultivars where it increases by about three fold during the cold acclimation period. Exogenous betaine application resulted in a large increase in total osmolality mostly due to betaine accumulation. Plants that accumulated betaine are more tolerant to freezing stress since a four day exposure to 250 mM betaine resulted in a LT50 of −8°C (in spring wheat Glenlea) and −9°C (in winter wheat Fredrick) compared to −3°C (Glenlea) and −4°C (Fredrick) for control non-exposed plants. Betaine treatment (250 mM) during cold acclimation increased FT in an additive manner since the LT50 reached −14°C (Glenlea) and −22°C (Fredrick) compared to −8°C (Glenlea) and −16°C (Fredrick) for plants that are cold acclimated in the absence of betaine. These results show that betaine treatment can improve FT by more than 5°C in both non-acclimated and cold-acclimated plants. The betaine treatment resulted in the induction of a subset of low temperature responsive genes, such as the wcor410, and wcor413, that are also induced by salinity or drought stresses. In addition to these genetic responses, betaine treatment was also able to improve the tolerance to photoin-hibition of PSII and the steady-state yield of electron transport over PSII in a manner that mimicked cold-acclimated plants. These data also suggest that betaine improves FT by eliciting some of the genetic and physiological responses associated with cold acclimation. [ABSTRACT FROM AUTHOR]

To elucidate the molecular basis of cold acclimation in strawberry (Fragaria × anannassa), we have begun studies to identify genes associated with low temperature (LT) acclimation. Differential screening of a cDNA library prepared from cold-acclimated strawberry plants allowed us to isolate several cDNAs showing differential expression at LT. Northern analysis showed that the transcript level of Fcorl (Fragaria cold-regulated) peaked after 2 days of LT exposure while that of Fcor2 peaked after 2 weeks. On the other hand, the level of Fcor3 transcript decreased within 24 hours of LT exposure and remained low during the 8 weeks acclimation period. Fcorl and Fcor2 are expressed in all tissues while Fcor3 is specific to leaves. The Fcorl-encoded protein has a compositional bias for leucine, isoleucine, glycine, proline and serine. This protein shares homology with the proteins encoded by blt101, a LT-re-sponsive gene from barley, and ESI3, a gene induced by salt stress in Lophopyrum. The FCOR2 protein is rich in lysine, leucine, valine, alanine and arginine, and shows no homology with any known gene products. The partial Fcor3 cDNA clone encodes a polypeptide that shows a very high identity with the spinach PSI subunit V and with the PSI PsaG polypeptide from barley. The level of Fcor1 transcript accumulation is correlated with the freezing tolerance of the strawberry cultivars used in our study. This suggests that Fcorl may be useful as a molecular marker to select for this trait in related species of the Rosaceae family. [ABSTRACT FROM AUTHOR]

The article discusses a research on changes in gene expression of the einkorn wheat mutant mvp-1 (maintained vegetative phase 1) and the role of jasmonate in vernalization and flowering in wheat plants as of 2014. The topics discussed include accumulation of methyl jasmonate (MeJA) in hexaploid winter wheat during cold exposure, role of MeJA in floral transitions of the plant, and the results of transcriptome analysis of wheat mvp mutants.