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Background Controlled turnover of proteins as mediated by the ubiquitin proteasome system (UPS) is an important element in plant defense against environmental and pathogen stresses. E3 ligases play a central role in subjecting proteins to hydrolysis by the UPS. Recently, it has been demonstrated that a specific class of E3 ligases termed the U-box ligases are directly associated with the defense mechanisms against abiotic and biotic stresses in several plants. However, no studies on U-box E3 ligases have been performed in one of the important staple crops, barley. Results In this study, we identified 67 putative U-box E3 ligases from the barley genome and expressed sequence tags (ESTs). Similar to Arabidopsis and rice U-box E3 ligases, most of barley U-box E3 ligases possess evolutionary well-conserved domain organizations. Based on the domain compositions and arrangements, the barley U-box proteins were classified into eight different classes. Along with this new classification, we refined the previously reported classifications of U-box E3 ligase genes in Arabidopsis and rice. Furthermore, we investigated the expression profile of 67 U-box E3 ligase genes in response to drought stress and pathogen infection. We observed that many U-box E3 ligase genes were specifically up-and-down regulated by drought stress or by fungal infection, implying their possible roles of some U-box E3 ligase genes in the stress responses. Conclusion This study reports the classification of U-box E3 ligases in barley and their expression profiles against drought stress and pathogen infection. Therefore, the classification and expression profiling of barley U-box genes can be used as a platform to functionally define the stress-related E3 ligases in barley. Electronic supplementary material The online version of this article (10.1186/s12864-019-5696-z) contains supplementary material, which is available to authorized users.

Under heat stress, polyunsaturated acyl groups, such as α-linolenate (18:3) and hexadecatrienoate (16:3), are removed from chloroplastic glycerolipids in various plant species. Here, we showed that a lipase designated HEAT INDUCIBLE LIPASE1 (HIL1) induces the catabolism of monogalactosyldiacylglycerol (MGDG) under heat stress in Arabidopsis thaliana leaves. Using thermotolerance tests, a T-DNA insertion mutant with disrupted HIL1 was shown to have a heat stress-sensitive phenotype. Lipidomic analysis indicated that the decrease of 34:6-MGDG under heat stress was partially impaired in the hil1 mutant. Concomitantly, the heat-induced increment of 54:9-triacylglycerol in the hil1 mutant was 18% lower than that in the wild-type plants. Recombinant HIL1 protein digested MGDG to produce 18:3-free fatty acid (18:3-FFA), but not 18:0- and 16:0-FFAs. A transient assay using fluorescent fusion proteins confirmed chloroplastic localization of HIL1. Transcriptome coexpression network analysis using public databases demonstrated that the HIL1 homolog expression levels in various terrestrial plants are tightly associated with chloroplastic heat stress responses. Thus, HIL1 encodes a chloroplastic MGDG lipase that releases 18:3-FFA in the first committed step of 34:6 (18:3/16:3)-containing galactolipid turnover, suggesting that HIL1 has an important role in the lipid remodeling process induced by heat stress in plants.

Main conclusion UGT79B31 encodes flavonol 3- O -glycoside: 2″- O -glucosyltransferase, an enzyme responsible for the terminal modification of pollen-specific flavonols in Petunia hybrida. Flavonoids are known to be involved in pollen fertility in petunia (P. hybrida) and maize (Zea mays). As a first step toward elucidating the role of flavonoids in pollen, we have identified a glycosyltransferase that is responsible for the terminal modification of petunia pollen-specific flavonoids. An in silico search of the petunia transcriptome database revealed four candidate UDP-glycosyltransferase (UGT) genes. UGT79B31 was selected for further analyses based on a correlation between the accumulation pattern of flavonol glycosides in various tissues and organs and the expression profiles of the candidate genes. Arabidopsis ugt79b6 mutants that lacked kaempferol/quercetin 3-O-glucosyl(1 → 2)glucosides, were complemented by transformation with UGT79B31 cDNA under the control of Arabidopsis UGT79B6 promoter, showing that UGT79B31 functions as a flavonol 3-O-glucoside: 2″-O-glucosyltransferase in planta. Recombinant UGT79B31 protein can convert kaempferol 3-O-galactoside/glucoside to kaempferol 3-O-glucosyl(1 → 2)galactoside/glucoside. UGT79B31 prefers flavonol 3-O-galactosides to the 3-O-glucosides and rarely accepted the 3-O-diglycosides as sugar acceptors. UDP-glucose was the preferred sugar donor for UGT79B31. These results indicated that UGT79B31 encodes a flavonoid 3-O-glycoside: 2″-O-glucosyltransferase. Transient expression of UGT79B31 fused to green fluorescent protein (GFP) in Nicotiana benthamiana showed that UGT79B31 protein was localized in the cytosol. Electronic supplementary material The online version of this article (10.1007/s00425-017-2822-5) contains supplementary material, which is available to authorized users.

Barley (Hordeum vulgare L.) produces five leucine-derived hydroxynitrile glucosides (HNGs), of which only epiheterodendrin is a cyanogenic glucoside. The four non-cyanogenic HNGs are the β-HNG epidermin and the γ-HNGs osmaronin, dihydroosmaronin and sutherlandin. By analyzing 247 spring barley lines including landraces and old and modern cultivars, we demonstrated that the HNG level varies notably between lines whereas the overall ratio between the compounds is constant. Based on sequence similarity to the sorghum (Sorghum bicolor) genes involved in dhurrin biosynthesis, we identified a gene cluster on barley chromosome 1 putatively harboring genes that encode enzymes in HNG biosynthesis. Candidate genes were functionally characterized by transient expression in Nicotiana benthamiana. Five multifunctional P450s, including two CYP79 family enzymes and three CYP71 family enzymes, and a single UDP-glucosyltransferase were found to catalyze the reactions required for biosynthesis of all five barley HNGs. Two of the CYP71 enzymes needed to be co-expressed for the last hydroxylation step in sutherlandin synthesis to proceed. This observation, together with the constant ratio between the different HNGs, suggested that HNG synthesis in barley is organized within a single multi-enzyme complex.

Significance Withanolides form a major class of plant steroids with unique side-chain modifications. Withanolides are one of the main active components in an Indian Ayurvedic medicinal plant, ashwagandha, which has been used for over 3,000 y. Because of their highly diversified structures, withanolides are promising pharmacological compounds with proven antiinflammatory and anticancer properties. We identified a sterol Δ24-isomerase (24ISO) catalyzing the first committed step in the biosynthesis of withanolides and related compounds. Identification of 24ISO paves the way for targeted manipulations to increase withanolide yields and as a starting point to elucidate the downstream pathway of yet-unknown withanolide biosynthesis. This study also demonstrates how the evolution of enzymes catalyzing double-bond modifications of triterpene side chains lead to diversity in structures and functions., A large part of chemodiversity of plant triterpenes is due to the modification of their side chains. Reduction or isomerization of double bonds in the side chains is often an important step for the diversification of triterpenes, although the enzymes involved are not fully understood. Withanolides are a large group of structurally diverse C28 steroidal lactones derived from 24-methylenecholesterol. These compounds are found in the Indian medicinal plant Withania somnifera, also known as ashwagandha, and other members of the Solanaceae. The pathway for withanolide biosynthesis is unknown, preventing sustainable production via white biotechnology and downstream pharmaceutical usages. In the present study, based on genome and transcriptome data we have identified a key enzyme in the biosynthesis of withanolides: a DWF1 paralog encoding a sterol Δ24-isomerase (24ISO). 24ISO originated from DWF1 after two subsequent duplication events in Solanoideae plants. Withanolides and 24ISO appear only in the medicinal plants in the Solanoideae, not in crop plants such as potato and tomato, indicating negative selection during domestication. 24ISO is a unique isomerase enzyme evolved from a reductase and as such has maintained the FAD-binding oxidoreductase structure and requirement for NADPH. Using phylogenetic, metabolomic, and gene expression analysis in combination with heterologous expression and virus-induced gene silencing, we showed that 24ISO catalyzes the conversion of 24-methylenecholesterol to 24-methyldesmosterol. We propose that this catalytic step is the committing step in withanolide biosynthesis, opening up elucidation of the whole pathway and future larger-scale sustainable production of withanolides and related compounds with pharmacological properties.

A large part of chemodiversity of plant triterpenes is due to the modification of their side chains. Reduction or isomerization of double bonds in the side chains is often an important step for the diversification of triterpenes, although the enzymes involved are not fully understood. Withanolides are a large group of structurally diverse C28 steroidal lactones derived from 24-methylenecholesterol. These compounds are found in the Indian medicinal plant Withania somnifera, also known as ashwagandha, and other members of the Solanaceae. The pathway for withanolide biosynthesis is unknown, preventing sustainable production via white biotechnology and downstream pharmaceutical usages. In the present study, based on genome and transcriptome data we have identified a key enzyme in the biosynthesis of withanolides: a DWF1 paralog encoding a sterol Δ24-isomerase (24ISO). 24ISO originated from DWF1 after two subsequent duplication events in Solanoideae plants. Withanolides and 24ISO appear only in the medicinal plants in the Solanoideae, not in crop plants such as potato and tomato, indicating negative selection during domestication. 24ISO is a unique isomerase enzyme evolved from a reductase and as such has maintained the FAD-binding oxidoreductase structure and requirement for NADPH. Using phylogenetic, metabolomic, and gene expression analysis in combination with heterologous expression and virus-induced gene silencing, we showed that 24ISO catalyzes the conversion of 24-methylenecholesterol to 24-methyldesmosterol. We propose that this catalytic step is the committing step in withanolide biosynthesis, opening up elucidation of the whole pathway and future larger-scale sustainable production of withanolides and related compounds with pharmacological properties.

SUMMARYWe have characterized a b–glucuronosyltransferase (AtGlcAT14A) from Arabidopsis thaliana that is involvedin the biosynthesis of type II arabinogalactan (AG). This enzyme belongs to the Carbohydrate ActiveEnzyme database glycosyltransferase family 14 (GT14). The protein was localized to the Golgi apparatuswhen transiently expressed in Nicotiana benthamiana. The soluble catalytic domain expressed in Pichia pas-toris transferred glucuronic acid (GlcA) to b–1,6–galactooligosaccharides with degrees of polymerization(DP) ranging from 3–11, and to b–1,3–galactooligosaccharides of DP5 and 7, indicating that the enzyme is aglucuronosyltransferase that modifies both the b–1,6- and b–1,3-galactan present in type II AG. Two allelicT–DNA insertion mutant lines showed 20–35% enhanced cell elongation during seedling growth comparedto wild-type. Analyses of AG isolated from the mutants revealed a reduction of GlcA substitution on Gal–b–1,6–Gal and b–1,3–Gal, indicating an in vivo role of AtGlcAT14A in synthesis of those structures in type IIAG. Moreover, a relative increase in the levels of 3-, 6- and 3,6-linked galactose (Gal) and reduced levels of3-, 2- and 2,5-linked arabinose (Ara) were seen, suggesting that the mutation in AtGlcAT14A results in a rela-tive increase of the longer and branched b–1,3- and b–1,6-galactans. This increase of galactosylation in themutants is most likely caused by increased availability of the O6 position of Gal, which is a shared acceptorsite for AtGlcAT14A and galactosyltransferases in synthesis of type II AG, and thus addition of GlcA may ter-minate Gal chain extension. We discuss a role for the glucuronosyltransferase in the biosynthesis of type IIAG, with a biological role during seedling growth.Keywords: glycosyltransferase family 14, glucuronosyltransferase, arabinogalactan protein, type II arabino-galactan, plant cell wall, Golgi apparatus, Arabidopsis thaliana.INTRODUCTIONThe arabinogalactan proteins (AGPs, AG proteins) belongto a highly diverse class of glycoproteins present on cellsurfaces of plants (Seifert and Roberts, 2007; Ellis et al.,2010; Tan et al., 2012). AGPs consist mainly of glycans(>90% w/w), and are synthesized by post-translationalmodification in the secretory pathway. The importance ofthe carbohydrate moieties of AGPs in various cellularprocesses has been reported, including somatic embryo-genesis, cell–cell interactions and cell elongation (Seifertand Roberts, 2007). Most of these studies involved use ofmonoclonal antibodies raised against the AG polysaccha-rides, and a temporal and spatial appearance of specificAG epitopes during development has been reported.However, as the precise epitope structure for most of the

Since the beginning of the financial and economic crises many news came to light which discussed the increasing number of non-performing loans, and the fact that as a result of the company break-downs, the bank portfolios have also gone worse and worse. In this paper our goal is to find out which internal factors influence the solvency of a company, therefore, to point out the weaknesses of the current Romanian rating systems, which as we will see, do not take into only relevant criteria when according a loan to a company. In order to conduct this study, we choose 18 indicators from several categories to predict bankruptcy. Some of the indicators mentioned above are really common in the international and the Romanian literature (e.g. ROA, ROE, ROS, assets turnover ratio), some of them are less. On a sample of 3000 Romanian companies we use the T-test statistical method to find out if an indicator is significant or not. The sample consists of companies (defaulted and non-defaulted as well) which have presented their financial statements (balance, profit and loss account between 1999 and 2008). For each company a set of 18 financial indicators was calculated, but the results obtained show that only 8 of them is significant in predicting bankruptcy: ROA, assets turnover ratio, equity/total assets, general leverage, current assets to total assets, cash to total assets, total assets and sales. In the next step, by analyzing the obligatory forms used in credit lending, we conclude which indicators are used by different Romanian commercial banks. We found that only four out of seven banks calculate all of the significant indicators identified in the first part of the paper. Finally, we made a proposal about which quantitative indicators should the banks use to minimize the credit losses and to avoid the overdue payments. In addition, we consider that the banks should pay attention to the qualitative factors as well to effectively filter out non-performing loans.

Plants growing in proximity to other plants are exposed to a variety of metabolites that these neighbors release into the environment. Some species produce allelochemicals to inhibit growth of neighboring plants, which in turn have evolved ways to detoxify these compounds. In order to understand how the allelochemical-receiving target plants respond to chemically diverse compounds, we performed whole-genome transcriptome analysis of Arabidopsis thaliana exposed to either the benzoxazinoid derivative 2-amino-3H-phenoxazin-3-one (APO) or momilactone B. These two allelochemicals belong to two very different compound classes, benzoxazinoids and diterpenes, respectively, produced by different cereal crop species. Despite their distinct chemical nature, we observed similar molecular responses of A. thaliana to these allelochemicals. In particular, many of the same or closely related genes belonging to the three-phase detoxification pathway were upregulated in both treatments. Further, we observed an overlap between genes upregulated by allelochemicals and those involved in herbicide detoxification. Our findings highlight the overlap in the transcriptional response of a target plant to natural and synthetic phytotoxic compounds and illustrate how herbicide resistance could arise via pathways involved in plant-plant interaction.