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Fusarium graminearum is a mycotoxin-producing pathogen involved in Fusarium head blight (FHB) disease of cereals, and is responsible for compromising grain yield and quality.Over the course of infection, the fungus secretes various metabolites and proteins, of which only a handful have been fully characterized in the context of FHB. We report herein the role of a secreted cerato-platanin protein (FGSG_10212, FgCPP1) in the growth and aggressiveness of F. graminearum. Pathogen strains in which FgCPP1 was disrupted (Δfgcpp1) or overexpressed (FgCPP1-OX1) did not differ from the wild-type with respect to macroconidial germination or mycelial growth, nor in sensitivity to chemicals targeting fungal cell walls. Host—plant interaction studies were conducted including disease assays in wheat and host-cell localization of FgCPP1 in tobacco cells. Consistent with previous reports for FgCPP1 disruption mutants of F. graminearum, no difference was observed among FgCPP1-OX1, Δfgcpp1 and the wild-type in their ability to cause disease spread in point-inoculated wheat spikes. Spray inoculation of the wheat spikes with FgCPP1-OX1 resulted in an increase in diseased spikelets as early as 3 days post-inoculation in each of the three wheat genotypes assessed; however, this increase was not observed when the disease assay was repeated in the cultivar ‘Penhold’ with an additional FgCPP1-OX transformant, FgCPP1-OX2. FgCPP1-OX1 also resulted in increased levels of deoxynivalenol accumulation in axenic culture, as well as in spray-inoculated wheat spikes. We propose that FgCPP1 is a minor contributor to pathogen aggressiveness in wheat.

Plant signaling hormones such as ethylene have been shown to affect the host response to various pathogens. Often, the resistance responses to necrotrophic fungi are mediated through synergistic interactions of ethylene (ET) with the jasmonate signaling pathway. On the other hand, ET is also an inducer of senescence and cell death, which could be beneficial for some invading necrotrophic pathogens. Fusarium graminearum, a causative agent in Fusarium head blight of wheat, is a hemibiotrophic pathogen, meaning it has both biotrophic and necrotrophic phases during the course of infection. However, the role of ET signaling in the host response to Fusarium spp. is unclear; some studies indicate that ET mediates resistance, while others have shown that it is associated with susceptibility. These discrepancies could be related to various aspects of different experimental designs, and suggest that the role of ET signaling in the host response to FHB is potentially dependent on interactions with some undetermined factors. To investigate whether wheat genotype can influence the ET-mediated response to FHB, the effect of chemical treatments affecting the ET pathway was studied in six wheat genotypes in detached-head assays. ET-inhibitor treatments broke down resistance to both initial infection and disease spread in three resistant wheat genotypes, whereas ET-enhancer treatments resulted in reduced susceptibility in three susceptible genotypes. The results presented here show that the ET signaling can mediate FHB resistance to F. graminearum in different wheat backgrounds.

The contribution of biological nitrogen fixation to the total N requirement of food and feed crops diminished in importance with the advent of synthetic N fertilizers, which fueled the “green revolution”. Despite being environmentally unfriendly, the synthetic versions gained prominence primarily due to their low cost, and the fact that most important staple crops never evolved symbiotic associations with bacteria. In the recent past, advances in our knowledge of symbiosis and nitrogen fixation and the development and application of recombinant DNA technology have created opportunities that could help increase the share of symbiotically-driven nitrogen in global consumption. With the availability of molecular biology tools, rapid improvements in symbiotic characteristics of rhizobial strains became possible. Further, the technology allowed probing the possibility of establishing a symbiotic dialogue between rhizobia and cereals. Because the evolutionary process did not forge a symbiotic relationship with the latter, the potential of molecular manipulations has been tested to incorporate a functional mechanism of nitrogen reduction independent of microbes. In this review, we discuss various strategies applied to improve rhizobial strains for higher nitrogen fixation efficiency, more competitiveness and enhanced fitness under unfavorable environments. The challenges and progress made towards nitrogen self-sufficiency of cereals are also reviewed. An approach to integrate the genetically modified elite rhizobia strains in crop production systems is highlighted.

Ripening of tomato fruit leads, in general, to a sequential decrease in the endogenous levels of polyamines spermidine (SPD) and spermine (SPM), while the trend for the diamine putrescine (PUT) levels is generally an initial decrease, followed by a substantial increase, and thereafter reaching high levels at the red ripe fruit stage. However, genetic engineering fruit-specific expression of heterologous yeast S-adenosylmethionine (SAM) decarboxylase in tomato has been found to result in a high accumulation of SPD and SPM at the cost of PUT. This system enabled a genetic approach to determine the impact of increased endogenous levels of biogenic amines SPD and SPM in tomato (579HO transgenic line) and on the biogenesis, transcription, processing, and stability of ribosomal RNA (rRNA) genes in tomato fruit as compared with the non-transgenic 556AZ line. One major biogenetic process regulating transcription and processing of pre-mRNA complexes in the nucleus involves small nucleolar RNAs (snoRNAs). To determine the effect of high levels of SPD and SPM on these latter processes, we cloned, sequenced, and identified a box C/D snoRNA cluster in tomato, namely, SlSnoR12, SlU24a, Slz44a, and Slz132b. Similar to this snoRNA cluster housed on chromosome (Chr.) 6, two other noncoding C/D box genes, SlsnoR12.2 and SlU24b, with a 94% identity to those on Chr. 6 were found located on Chr. 3. We also found that other snoRNAs divisible into snoRNA subclusters A and B, separated by a uridine rich spacer, were decorated with other C/D box snoRNAs, namely, J10.3, Z131a/b, J10.1, and Z44a, followed by z132a, J11.3, z132b, U24, Z20, U24a, and J11. Several of these, for example, SlZ44a, Slz132b, and SlU24a share conserved sequences similar to those in Arabidopsis and rice. RNAseq analysis of high SPD/SPM transgenic tomatoes (579HO line) showed significant enrichment of RNA polymerases, ribosomal, and translational protein genes at the breaker+8 ripening stage as compared with the 556AZ control. Thus, these results indicate that SPD/SPM regulates snoRNA and rRNA expression directly or indirectly, in turn, affecting protein synthesis, metabolism, and other cellular activities in a positive manner.

In differential gene expression data analysis, one objective is to identify groups of co-expressed genes from a large dataset to detect the association between such a group of genes and a phenotypic trait. This is often done through a clustering approach, such as k-means or bipartition hierarchical clustering, based on particular similarity measures in the grouping process. In such a dataset, the gene differential expression itself is an innate attribute that can be used in the feature extraction process. For example, in a dataset consisting of multiple treatments versus their controls, the expression of a gene in each treatment would have three possible behaviors, up-, down- regulated, or unchanged. We propose here a differential expression feature extraction (DEFE) method by using a string consisting of three numerical values at each character to denote such behavior, i.e. 1=up, 2=down, and 0=unchanged, which results in up to 3B differential expression patterns across all B comparisons. This approach has been successfully applied in many datasets, of which we present in this study two sets of RNA-sequencing (RNA-seq) data on wheat challenged with stress related phytohormones or Fusarium graminearum, the causal agent of fusarium head blight (FHB), a devastating wheat disease to illustrate the algorithm. Combinations of multiple schemes of DEFE patterns revealed groups of genes putatively associated with resistance or susceptibility to FHB. DEFE enabled discovery of genes closely associated with defense related signaling molecules such as JAZ10, shikimate and chorismate biosynthesis pathway and groups of wheat genes with differential effects between more or less virulent strains of Fusarium graminearum.

Plant signaling hormones such as ethylene have been shown to affect the host response to various pathogens. Often, the resistance responses to necrotrophic fungi are mediated through synergistic interactions of ethylene (ET) with the jasmonate signaling pathway. On the other hand, ET is also an inducer of senescence and cell death, which could be beneficial for some invading necrotrophic pathogens.

Background The mitogen-activated protein kinase (MAPK) family is involved in signal transduction networks that underpin many different biological processes in plants, ranging from development to biotic and abiotic stress responses. To date this class of enzymes has received little attention in Triticeae species, which include important cereal crops (wheat, barley, rye and triticale) that represent over 20% of the total protein food-source worldwide. Results The work presented here focuses on two subfamilies of Triticeae MAPKs, the MAP kinases (MPKs), and the MAPK kinases (MKKs) whose members phosphorylate the MPKs. In silico analysis of multiple Triticeae sequence databases led to the identification of 152 MAPKs belonging to these two sub-families. Some previously identified MAPKs were renamed to reflect the literature consensus on MAPK nomenclature. Two novel MPKs, MPK24 and MPK25, have been identified, including the first example of a plant MPK carrying the TGY activation loop sequence common to mammalian p38 MPKs. An EF-hand calcium-binding domain was found in members of the Triticeae MPK17 clade, a feature that appears to be specific to Triticeae species. New insights into the novel MEY activation loop identified in MPK11s are offered. When the exon-intron patterns for some MPKs and MKKs of wheat, barley and ancestors of wheat were assembled based on transcript data in GenBank, they showed deviations from the same sequence predicted in Ensembl. The functional relevance of MAPKs as derived from patterns of gene expression, MPK activation and MKK-MPK interaction is discussed. Conclusions A comprehensive resource of accurately annotated and curated Triticeae MPK and MKK sequences has been created for wheat, barley, rye, triticale, and two ancestral wheat species, goat grass and red wild einkorn. The work we present here offers a central information resource that will resolve existing confusion in the literature and sustain expansion of MAPK research in the crucial Triticeae grains. Electronic supplementary material The online version of this article (10.1186/s12864-018-4545-9) contains supplementary material, which is available to authorized users.

Crop losses due to pathogens are a major threat to global food security. Plants employ a multilayer defense against a pathogen including the use of physical barriers (cell wall), induction of hypersensitive defense response (HR), resistance (R) proteins, and synthesis of antimicrobial peptides (AMPs). Unlike a complex R gene-mediated immunity, AMPs directly target diverse microbial pathogens. Many a times, R-mediated immunity breaks down and plant defense is compromised. Although R-gene dependent pathogen resistance has been well studied, comparatively little is known about the interactions of AMPs with host defense and physiology. AMPs are ubiquitous, low molecular weight peptides that display broad spectrum resistance against bacteria, fungi and viruses. In plants, AMPs are mainly classified into cyclotides, defensins, thionins, lipid transfer proteins, snakins, and hevein-like vicilin-like and knottins. Genetic distance lineages suggest their conservation with minimal effect of speciation events during evolution. AMPs provide durable resistance in plants through a combination of membrane lysis and cellular toxicity of the pathogen. Plant hormones - gibberellins, ethylene, jasmonates, and salicylic acid, are among the physiological regulators that regulate the expression of AMPs. Transgenically produced AMP-plants have become a means showing that AMPs are able to mitigate host defense responses while providing durable resistance against pathogens.

International audience; Plants execute an array of mechanisms in response to stress which include upregulation of defense related-proteins and changes in specific metabolites. Polyamines - putrescine (Put), spermidine (Spd), and spermine (Spm) - are metabolites commonly found associated with abiotic stresses such as chilling stress. We have generated two transgenic tomato lines (556HO and 579HO) that express yeast S-adenosylmethionine decarboxylase and specifically accumulate Spd and Spm in fruits in comparison to fruits from control (556AZ) plants (Mehta et al., 2002). Tomato fruits undergo chilling injury at temperatures below 13 degrees C. The high Spd and Spm tomato together with the control azygous line were utilized to address role(s) of polyamines in chilling-injury signaling. Exposure to chilling temperature (2 degrees C) led to several-fold increase in the Put content in all the lines. Upon re-warming of the fruits at 20 degrees C, the levels of Spd and Spm increased further in the fruit of the two transgenic lines, the higher levels remaining stable for 15 days after re-warming as compared to the fruit from the control line. Profiling their steady state proteins before and after re-warming highlighted a protein of similar to 14 kD. Using proteomics approach, protein sequencing and immunoblotting, the similar to 14 kD protein was identified as the pathogenesis related protein 1b1 (PR1b1). The PR1b1 protein accumulated transiently in the control fruit whose level was barely detectable at d 15 post-warming while in the fruit from both the 556HO and 579HO transgenic lines PR1b1 abundance increased and remained stable till d 15 post warming. PR1b1 gene transcripts were found low in the control fruit with a visible accumulation only on d 15 post warming; however, in both the transgenic lines it accumulated and increased soon after rewarming being several-fold higher on day 2 while in 556HO line this increase continued until d 6 than the control fruit. The chilling-induced increase in PR1b1 protein seems independent of ethylene and methyl jasmonate signaling but may be linked to salicylic acid. We propose that polyamine-mediated sustained accumulation of PR1b1 protein in post-warmed chilled tomato fruit is a pre-emptive cold stress response and possibly a defense response mechanism related to Cold Stress-Induced Disease Resistance (SIDR) phenomenon.

Disease afflicts crop productivity as well as nutritional attributes. Pathogens have the ability to mutate rapidly and thereby develop resistance to pesticides. Despite plant’s multilayer of innate defence against pathogens, often the latter are able to penetrate and establish themselves on plant host. The discovery of antimicrobial peptides (AMPs) has the promise of durable defence by quickly eliminating pathogens through membrane lysis. AMPs characteristically are made up of from fewer than 20 amino acids to about 100 amino acids, and yet are structurally diverse. AMPs in plants are classified into cyclotides, defensins, lipid transfer proteins (LTPs), thionins, snakins, hevein-like peptides, knottin-type peptides, and others. It is important to characterize and study mechanism of their action in order to develop a wide range of structures with the potential to provide durable plant immunity against pathogens. We bring together recent information on the mechanisms by which AMPs are able to help the plant to thwart pathogen attack. Although permeabilizing cellular membrane is a major mechanism known for AMP action, new and diverse modes of action have recently been unearthed, including targeting of intracellular function of the pathogen.

Triticale, a man-made cereal crop developed from a cross between wheat and rye, has excellent agronomic traits to produce starch for bioindustrial applications. The effects of different levels of water stress on expression of starch synthesis genes and starch composition and physicochemical properties were investigated in this study. Three triticale varieties from 5 days post-anthesis were treated with three levels of water stress: low water stress (LWS) at 55–60% of soil moisture, moderate water stress (MWS) at 30–35% soil moisture and severe water stress (SWS) at 10–15% soil moisture. Water stress led to a significant reduction in seed weight at SWS (35–45%). A decrease in starch content was noticeable from MWS onwards and the values were decreased by 42–55% at SWS across all varieties. Such decrease was associated with the reduced expression of starch synthesis genes at 19 days of water stress (DWS). MWS favoured an increase of amylose proportion in triticale starch and it was accompanied by a significant up-regulation of GBSSI expression throughout the grain development. Triticale starch synthesized under water stress showed a reduced population of small granules and an increase of A-type to B-type ratio. SWS caused pitting on starch granules but did not alter the biconcave disc shape of mature granules. An inverse relationship between water stress and a range of starch gelatinization temperature was observed and the MWS environment specifically decreased the peak temperature ( T p) and increased the enthalpy. Our results signify that starch morphology, composition and physicochemical properties in triticale grains could be altered if triticale is grown under drought conditions.

Vegetables and fruits are essential components of the human diet as they are sources of vitamins, minerals, and fiber and provide antioxidants that prevent chronic diseases. Our goal is to improve durable nutritional quality of tomato fruit. We developed transgenic tomatoes expressing yeast S-adenosylmethionine decarboxylase (ySAMdc) gene driven by a fruit-specific E8 promoter to investigate the role of polyamines in fruit metabolism. Stable integration of E8-ySAMdc chimeric gene in tomato genome led to ripening-specific accumulation of polyamines, spermidine (Spd) and spermine (Spm), which in turn affected higher accumulation of glutamine, asparagine, and organic acids in the red fruit with significant decrease in the contents of valine, aspartate, sucrose, and glucose. The metabolite profiling analysis suggests that Spd/Spm are perceived as signaling organic-N metabolites by the fruit cells, resulting in the stimulation of carbon sequestration; enhanced synthesis of biomolecules; increased acid to sugar ratio, a good attribute for the fruit flavor; and in the accumulation of another vital amine, choline, which is an essential micronutrient for brain development. A limited transcriptome analysis of the transgenic fruit that accumulate higher polyamines revealed a large number of differentially expressed genes, about 55 of which represented discrete functional categories, and the remaining 45 were novel, unknown, or unclassified: amino acid biosynthesis, carotenoid biosynthesis, cell wall metabolism, chaperone family, flavonoid biosynthesis, fruit ripening, isoprenoid biosynthesis, polyamine biosynthesis, signal transduction, stress/defense-related, transcription, translation, and vacuolar function. There was a good correspondence between some gene transcripts and their protein products, but not in the case of the tonoplast intrinsic protein, which showed post-transcriptional regulation. Higher metabolic activity of the transgenic fruit is reflected in higher respiratory activity, and upregulation of chaperones and mitochondrial cytochrome oxidase transcripts compared to the control. These transgenic plants are a new resource to understand the role of Spd/Spm in fruit biology. Transcriptome analysis and metabolic profiles of Spd/Spm accumulating, transgenic fruit suggest the presence of an intricate regulation and interconnection between certain metabolic pathways that are revived when Spd and Spm likely reach a certain threshold. Thus, polyamines act as antiapoptotic regulatory molecules and are able to revive metabolic memory in the tomato fruit.

Plum base wines prepared with potassium metabisulphite or sodium benzoate were converted into sparkling wine, either by `Methode Champenoise' or tank method with artificially carbonated wine serving as a control. In both the secondary fermentation methods ethanol and low temperature acclimatized yeast; Saccharomyces cerevisiae UCD-595 with optimized sugar (1.5%) and di-ammonium hydrogen phosphate (0.2%) were used. Both methods of sparkling wine production and the type of base wine affected the physico-chemical and sensory characteristics of the sparkling wine produced. In the secondary fermented wines, most of the physico-chemical characteristics were altered compared to that of artificially carbonated wines except volatile acidity, methanol, propanol and ethanol. Furthermore, these wines contained lower proteins, minerals and amyl alcohol than the base wine. In general, the sparkling wines produced by either of the secondary fermentation method had lower sugar, more alcohol, higher macro elements but lower Fe and Cu contents than the artificially carbonated wines. An overview of the changes occurring in the sparkling wine in comparison to artificially carbonated wine revealed that most of the changes took place due to secondary fermentation. The bottle fermented wine recorded the highest pressure, low TSS and sugars. The secondary bottle fermented wine was the best in most of the sensory qualities but needed proper acid-sugar blend of the base wine before conducting secondary fermentation. Sparkling wine made from base wine with sodium benzoate was preferred to that prepared with potassium metabisulphite. The studies showed the potential of plum fruits for production of sparkling wine.Os vinhos a base de ameixa preparado com metabisulfito de potássio ou benzoato de sódio foram convertidos em vinhos espumantes pelo método "Champenoise" ou método de tanque, usando vinho carbonatado artificialmente como controle. Em ambos métodos a fermentação secundária do ethanol a baixa temperatura aclimatizou a levedura Saccharomyces cerevisiae UCD-595 utilizando 1.5% de açúcar e 0.2% de fosfato di-amônio de hidrogênio. Não foi verificado nenhum tipo de alteração físico-química ou sensorial em nenhum dos métodos utilizados para a produção do vinho espumante Foram verificadas alterações físico-químicas na fermentação secundária do vinho espumante quando comparado com o vinho carbonatado artificialmente, exceto acidez volátil, metanol, propanol e ethanol. Além do mais, estes vinhos contiveram concentrações inferiores de proteínas, minerais e álcool amílico que o vinho de base. Em geral, os vinhos espumantes produzidos por qualquer método de fermentação secundária apresentaram açúcar residual baixo, concentrações elevadas de álcool, macroelementos elevados e concentrações baixas de Fe e Cu nos vinhos carbonatados artificialmente. Uma visão geral das mudanças que ocorrem no vinho espumante em comparação ao vinho carbonatado artificialmente demonstrou que a maioria das mudanças ocorreu devido a fermentação secundária. A garrafa do vinho fermentado registrou pressão elevada, TSS e açúcares residuais reduzidos. O Vinho espumante produzido utilizando benzoato de sódio foi preferido em relação ao preparado com metabissulfito de potássio. Esses estudos demostraram o potencial do uso de frutas como ameixa na produção de vinho espumante.

S-adenosylmethionine (SAM), a major substrate in 1-C metabolism is a common precursor in the biosynthetic pathways of polyamines and ethylene, two important plant growth regulators, which exhibit opposing developmental effects, especially during fruit ripening. However, the flux of various substrates including SAM into the two competing pathways in plants has not yet been characterized. We used radiolabeled (14)C-Arg, (14)C-Orn, L-[U-(14)C]Met, (14)C-SAM and (14)C-Put to quantify flux through these pathways in tomato fruit and evaluate the effects of perturbing these pathways via transgenic expression of a yeast SAM decarboxylase (ySAMDC) gene using the fruit ripening-specific promoter E8. We show that polyamines in tomato fruit are synthesized both from Arg and Orn; however, the relative contribution of Orn pathway declines in the later stages of ripening. Expression of ySAMDC reversed the ripening associated decline in spermidine (Spd) and spermine (Spm) levels observed in the azygous control fruit. About 2- to 3-fold higher levels of labeled-Spd in transgenic fruit (556HO and 579HO lines) expressing ySAMDC confirmed the enzymatic function of the introduced gene. The incorporation of L-[U-(14)C]Met into Spd, Spm, ethylene and 1-aminocyclopropane-1-carboxylic acid (ACC) was used to determine Met-flux into these metabolites. The incorporation of (14)C-Met into Spd/Spm declined during ripening of the control azygous fruit but this was reversed in fruits expressing ySAMDC. However, incorporation of (14)C-Met into ethylene or ACC during ripening was not altered by the expression of ySAMDC in the fruit. Taken together these results show that: (1) There is an inverse relationship between the production of higher polyamines and ethylene during fruit ripening, (2) the inverse relationship between higher polyamines and ethylene is modulated by ySAMDC expression in that the decline in Spd/Spm during fruit ripening can be reversed without significantly altering ethylene biosynthesis, and (3) cellular flux of SAM in plants is homeostatically regulated based on its demand for competing pathways.

Physical clustering of genes has been shown in plants; however, little is known about gene clusters that have different functions, particularly those expressed in the tomato fruit. A class I 17.6 small heat shock protein (Sl17.6 shsp) gene was cloned and used as a probe to screen a tomato (Solanum lycopersicum) genomic library. An 8.3-kb genomic fragment was isolated and its DNA sequence determined. Analysis of the genomic fragment identified intronless open reading frames of three class I shsp genes (Sl17.6, Sl20.0, and Sl20.1), the Sl17.6 gene flanked by Sl20.1 and Sl20.0, with complete 5' and 3' UTRs. Upstream of the Sl20.0 shsp, and within the shsp gene cluster, resides a box C/D snoRNA cluster made of SlsnoR12.1 and SlU24a. Characteristic C and D, and C' and D', boxes are conserved in SlsnoR12.1 and SlU24a while the upstream flanking region of SlsnoR12.1 carries TATA box 1, homol-E and homol-D box-like cis sequences, TM6 promoter, and an uncharacterized tomato EST. Molecular phylogenetic analysis revealed that this particular arrangement of shsps is conserved in tomato genome but is distinct from other species. The intronless genomic sequence is decorated with cis elements previously shown to be responsive to cues from plant hormones, dehydration, cold, heat, and MYC/MYB and WRKY71 transcription factors. Chromosomal mapping localized the tomato genomic sequence on the short arm of chromosome 6 in the introgression line (IL) 6-3. Quantitative polymerase chain reaction analysis of gene cluster members revealed differential expression during ripening of tomato fruit, and relatively different abundances in other plant parts.

Exogenous treatment with jasmonates (JA) has been shown to reduce the levels of polyamines in many plants. But the role of endogenous JA on polyamine biosynthesis or other cellular metabolites has thus far remained uninvestigated. We developed transgenic tomato (Solanum lycopersicum L.) having severely reduced methyl JA levels by silencing a fruit ripening-associated lipoxygenase (LOX), SlLoxB, using a truncated LOX gene under the control of the constitutive CaMV35S promoter. The LOX suppressed and MeJA-deficient fruits had lowered polyamine levels. Thus, these transgenic fruits were used as a plant model to evaluate the effects of reduced endogenous MeJA on cellular metabolites in ripening tomato fruits using NMR spectroscopy. During on-shelf ripening, transgenic fruits were significantly reduced in the content of 19 out of 30 metabolites examined, including Ile, Val, Ala, Thr, Asn Tyr, Glu, Gln, His, Phe, Trp, GABA, citrate, succinate, myo-inositol, unidentified compound B, nucleic acid compound Nucl1, choline, and trigonelline as compared to the wild-type azygous counterparts. A significant increase in β-glucose levels in transgenic fruits was observed at the pink stage. The transgenic fruits were equivalent to the wild type in lycopene level and chlorophyll degradation rates. Taken together, these results show that intracellular MeJA significantly regulates overall primary metabolism, especially aminome (amino acids and polyamines) of ripening fruits.

Detached ears of wheat were cultured in liquid medium manipulated for sucrose and glutamine contents, and the accumulation of starch and protein in relation to the activities of sucrose cleaving—, ammonia assimilating—, and transaminating enzymes was studied in the grain. With an increase in the concentrations of sucrose from 44 to 176 mM and glutamine from 6.4 to 25.7 mM (keeping their ratio at a constant value of 7:1), the contents of starch and protein increased in the grains. However, when the grains were cultured in the medium containing 8.5 to 34 mM glutamine and a fixed concentration of 117 mM sucrose, there was a gradual increase in protein and decrease in starch content in the grain. By such manipulation in the liquid medium, the content of free amino acids also increased in the grain up to 12 days culturing. Amongst sucrose cleaving enzymes, the activities of sucrose-UDP glucosyl transferase and soluble alkaline invertase were much lower than the activity of soluble acid invertase. At high concentration (34 mM) of glutamine in the medium, containing 117 mM sucrose, there was drastic decrease in the activities of soluble acid invertase and UDPG pyrophosphorylase but the activities of ADPG pyrophosphorylase, alkaline inorganic pyrophosphatase, glutamate dehydrogenase, glutamate oxaloacetate transaminase and glutamate pyruvate transaminase increased in the grain with increase in glutamine concentration in the culture medium. Evidently, an increase in the level of amino nitrogen, coupled with an optimum sucrose concentration in the grain raised through liquid culturing enhances the conversion of sucrose to protein at the cost of starch accumulation in wheat.

Unprecedented progress during the last three decades in our understanding of the principles of a living cell, particularly the identification of genes and signaling pathways involved in cell differentiation and organ development, has brought us a broader insight into plant biological processes. Technological advancements are revealing new and fundamental knowledge at the molecular and cellular levels, knowledge that is critical towards achieving the goal of precision-based crop improvement. Modernday genetic engineering has emerged as a promising precision-based technology for boosting up food production in the world and introducing desirable traits such as nutritional enhancement and disease and pest resistance, both important components of agricultural sustainability (Chrispeels et al. 2002; Fatima et al. 2008; Negi and Handa 2008). Achieving results that benefit the world will depend on the success of applying new knowledge to real-world field scenarios. The challenge, therefore, is also to simultaneously obtain knowledge on agroecosystem structure and function to understand how manipulation and control of specific gene expression will translate into directing processes at the ecological scale (Mattoo and Teasdale 2009). Developmental traits are coordinated at various levels in a plant and involve organ-to-organ communications via long-distance signaling processes that integrate transcription, hormonal action and environmental cues. Thus, plant architecture, root–soil–microbe interactions, flowering, fruit (and seed) development, and fruit ripening (and seed germination) are highly regulated genetic programs that are also impacted by processes such as organ abscission, organ senescence (and ripening), and programmed cell death (PCD). We note that belowground processes provide the anchor for a healthy and robust plant (Mattoo and Teasdale 2009) but in this

Polyamines are ubiquitous aliphatic amines that have been implicated in myriad processes, but their precise biochemical roles are not fully understood. We have carried out metabolite profiling analyses of transgenic tomato (Solanum lycopersicum) fruit engineered to accumulate the higher polyamines spermidine (Spd) and spermine (Spm) to bring an insight into the metabolic processes that Spd/Spm regulate in plants. NMR spectroscopic analysis revealed distinct metabolite trends in the transgenic and wild-type/azygous fruits ripened off the vine. Distinct metabolites (glutamine, asparagine, choline, citrate, fumarate, malate, and an unidentified compound A) accumulated in the red transgenic fruit, while the levels of valine, aspartic acid, sucrose, and glucose were significantly lower as compared to the control (wild-type and azygous) red fruit. The levels of isoleucine, glucose, γ-aminobutyrate, phenylalanine, and fructose remained similar in the nontransgenic and transgenic fruits. Statistical treatment of the metabolite variables distinguished the control fruits from the transgenic fruit and provided credence to the pronounced, differential metabolite profiles seen during ripening of the transgenic fruits. The pathways involved in the nitrogen sensing/signaling and carbon metabolism seem preferentially activated in the high Spd/Spm transgenics. The metabolite profiling analysis suggests that Spd and Spm are perceived as nitrogenous metabolites by the fruit cells, which in turn results in the stimulation of carbon sequestration. This is seen manifested in higher respiratory activity and up-regulation of phosphoenolpyruvate carboxylase and NADP-dependent isocitrate dehydrogenase transcripts in the transgenic fruit compared to controls, indicating high metabolic status of the transgenics even late in fruit ripening.

Antimicrobial cationic peptides (AMPs) are ubiquitous small proteins used by living cells to defend against a wide spectrum of pathogens. Their amphipathic property helps their interaction with negatively charged cellular membrane of the pathogen causing cell lysis and death. AMPs also modulate signaling pathway(s) and cellular processes in animal models; however, little is known of cellular processes other than the pathogen-lysis phenomenon modulated by AMPs in plants. An engineered heterologous AMP, msrA3, expressed in potato was previously shown to cause resistance of the transgenic plants against selected fungal and bacterial pathogens. These lines together with the wild type were studied for growth habits, and for inducible defense responses during challenge with biotic (necrotroph Fusarium solani) and abiotic stressors (dark-induced senescence, wounding and temperature stress). msrA3-expression not only conferred protection against F. solani but also delayed development of floral buds and prolonged vegetative phase. Analysis of select gene transcript profiles showed that the transgenic potato plants were suppressed in the hypersensitive (HR) and reactive oxygen species (ROS) responses to both biotic and abiotic stressors. Also, the transgenic leaves accumulated lesser amounts of the defense hormone jasmonic acid upon wounding with only a slight change in salicylic acid as compared to the wild type. Thus, normal host defense responses to the pathogen and abiotic stressors were mitigated by msrA3 expression suggesting MSRA3 regulates a common step(s) of these response pathways. The stemming of the pathogen growth and mitigating stress response pathways likely contributes to resource reallocation for higher tuber yield.