The cinnamyl alcohol dehydrogenase family in flax: Differentiation during plant growth and under stress conditions

Characterization of the Moroccan Barley Germplasm Preserved in the Polish Genebank as a First Step towards Selecting Forms with Increased Drought Tolerance

In marginal, arid, and semi-arid areas of Morocco, crops are often exposed to multiple abiotic and biotic stresses that have a major impact on yield. Farmer-maintained Moroccan landraces have been shaped by the impact of very strong selection pressures, gradually adapting to the local ecosystem and obsolete low-input agricultural practices without improvement towards high yield and quality. Considering the increasing threat of drought in Poland, it is necessary to introduce germplasm with tolerance to water deficit into barley breeding programs. The aim of this research was a DArTseq-based genetic characterization of a collection of germplasm of Moroccan origin, conserved in the Polish genebank. The results showed that all conserved landraces have a high level of heterogeneity and their gene pool is different from the material developed by Polish breeders. Based on the analysis of eco-geographical data, locations with extremely different intensities of drought stress were selected. A total of 129 SNPs unique to accessions from these locations were identified. In the neighborhood of the clusters of unique SNPs on chromosomes 5H and 6H, genes that may be associated with plant response to drought stress were identified. The results obtained may provide a roadmap for further research to support Polish barley breeding for increased drought tolerance.

Bisphenols-A Threat to the Natural Environment

Negative public sentiment built up around bisphenol A (BPA) follows growing awareness of the frequency of this chemical compound in the environment. The increase in air, water, and soil contamination by BPA has also generated the need to replace it with less toxic analogs, such as Bisphenol F (BPF) and Bisphenol S (BPS). However, due to the structural similarity of BPF and BPS to BPA, questions arise about the safety of their usage. The toxicity of BPA, BPF, and BPS towards humans and animals has been fairly well understood. The biodegradability potential of microorganisms towards each of these bisphenols is also widely recognized. However, the scale of their inhibitory pressure on soil microbiomes and soil enzyme activity has not been estimated. These parameters are extremely important in determining soil health, which in turn also influences plant growth and development. Therefore, in this manuscript, knowledge has been expanded and systematized regarding the differences in toxicity between BPA and its two analogs. In the context of the synthetic characterization of the effects of bisphenol permeation into the environment, the toxic impact of BPA, BPF, and BPS on the microbiological and biochemical parameters of soils was traced. The response of cultivated plants to their influence was also analyzed.

The discovery and characterization of AeHGO in the branching route from shikonin biosynthesis to shikonofuran in Arnebia euchroma

Shikonin derivatives are natural naphthoquinone compounds and the main bioactive components produced by several boraginaceous plants, such as Lithospermum erythrorhizon and Arnebia euchroma. Phytochemical studies utilizing both L. erythrorhizon and A. euchroma cultured cells indicate the existence of a competing route branching out from the shikonin biosynthetic pathway to shikonofuran. A previous study has shown that the branch point is the transformation from (Z)-3''-hydroxy-geranylhydroquinone to an aldehyde intermediate (E)-3''-oxo-geranylhydroquinone. However, the gene encoding the oxidoreductase that catalyzes the branch reaction remains unidentified. In this study, we discovered a candidate gene belonging to the cinnamyl alcohol dehydrogenase family, AeHGO, through coexpression analysis of transcriptome data sets of shikonin-proficient and shikonin-deficient cell lines of A. euchroma. In biochemical assays, purified AeHGO protein reversibly oxidized (Z)-3''-hydroxy-geranylhydroquinone to produce (E)-3''-oxo-geranylhydroquinone followed by reversibly reducing (E)-3''-oxo-geranylhydroquinone to (E)-3''-hydroxy-geranylhydroquinone, resulting in an equilibrium mixture of the three compounds. Time course analysis and kinetic parameters showed that the reduction of (E)-3''-oxo-geranylhydroquinone was stereoselective and efficient in presence of NADPH, which determined that the overall reaction proceeded from (Z)-3''-hydroxy-geranylhydroquinone to (E)-3''-hydroxy-geranylhydroquinone. Considering that there is a competition between the accumulation of shikonin and shikonofuran derivatives in cultured plant cells, AeHGO is supposed to play an important role in the metabolic regulation of the shikonin biosynthetic pathway. Characterization of AeHGO should help expedite the development of metabolic engineering and synthetic biology toward production of shikonin derivatives.

Transcriptomics and metabolomics reveal tolerance new mechanism of rice roots to Al stress

The prevalence of soluble aluminum (Al) ions is one of the major limitations to crop production worldwide on acid soils. Therefore, understanding the Al tolerance mechanism of rice and applying Al tolerance functional genes in sensitive plants can significantly improve Al stress resistance. In this study, transcriptomics and metabolomics analyses were performed to reveal the mechanism of Al tolerance differences between two rice landraces (Al-tolerant genotype Shibanzhan (KR) and Al-sensitive genotype Hekedanuo (MR) with different Al tolerance. The results showed that DEG related to phenylpropanoid biosynthesis was highly enriched in KR and MR after Al stress, indicating that phenylpropanoid biosynthesis may be closely related to Al tolerance. E1.11.1.7 (peroxidase) was the most significant enzyme of phenylpropanoid biosynthesis in KR and MR under Al stress and is regulated by multiple genes. We further identified that two candidate genes Os02g0770800 and Os06g0521900 may be involved in the regulation of Al tolerance in rice. Our results not only reveal the resistance mechanism of rice to Al stress to some extent, but also provide a useful reference for the molecular mechanism of different effects of Al poisoning on plants.

Systematic functional characterization of cinnamyl alcohol dehydrogenase family members revealed their functional divergence in lignin biosynthesis and stress responses in mulberry

Mulberry (Morus) is used as a feed additive and biofuel materials. Cinnamyl alcohol dehydrogenase (CAD; EC 1.1.1.95) catalyzes the final step of monolignol biosynthesis and is responsible for various monolignols. Five MaCADs from Morus alba were cloned and functionally characterized in the present study. These MaCADs encoded proteins with 357-364 amino acids, and the putative protein sequences conservatively possessed two Zn²⁺ binding motifs and an NADP(H) cofactor binding motif. However, MaCAD1, 2, and 5 shared similar amino acids at substrate binding positions that differed from those possessed by bona fide CADs. MaCAD3 and 4 had conservative substrate binding sites, and both phylogenetic and expression profile analysis indicated they were bona fide CADs involved in lignin biosynthesis. The enzymatic assay showed that MaCAD1 and 5 had a high affinity to p-coumaryl aldehyde. MaCAD4 preferentially used coniferyl aldehyde and sinapyl aldehyde as substrates. His-72 and Tyr-124 in MaCAD1 stabilized p-coumaryl aldehyde, and may have resulted in the substrate preference for p-coumaryl aldehyde. Down-regulation of MaCADs in mulberry showed that MaCAD3/4 were dominant CADs that functioned in monolignol biosynthesis, and decreased MaCAD3/4 resulted in significant decreases of lignin content in both stems and leaves. MaCADs exhibited different expression patterns in response to various stresses, indicating their possible diverse roles. MaCAD2 and MaCAD5 may play positive roles in response to drought and cold stresses, respectively. These results provide a systematic functional analysis of MaCADs in mulberry and an important foundation for the genetic modification of the monolignol pathway in mulberry.

Mechanistic Insights into Potassium-Conferred Drought Stress Tolerance in Cultivated and Tibetan Wild Barley: Differential Osmoregulation, Nutrient Retention, Secondary Metabolism and Antioxidative Defense Capacity

Keeping the significance of potassium (K) nutrition in focus, this study explores the genotypic responses of two wild Tibetan barley genotypes (drought tolerant XZ5 and drought sensitive XZ54) and one drought tolerant barley cv. Tadmor, under the exposure of polyethylene glycol-induced drought stress. The results revealed that drought and K deprivation attenuated overall plant growth in all the tested genotypes; however, XZ5 was least affected due to its ability to retain K in its tissues which could be attributed to the smallest reductions of photosynthetic parameters, relative chlorophyll contents and the lowest Na⁺/K⁺ ratios in all treatments. Our results also indicate that higher H⁺/K⁺-ATPase activity (enhancement of 1.6 and 1.3-fold for shoot; 1.4 and 2.5-fold for root), higher shoot K⁺ (2 and 2.3-fold) and Ca²⁺ content (1.5 and 1.7-fold), better maintenance of turgor pressure by osmolyte accumulation and enhanced antioxidative performance to scavenge ROS, ultimately suppress lipid peroxidation (in shoots: 4% and 35%; in roots 4% and 20% less) and bestow higher tolerance to XZ5 against drought stress in comparison with Tadmor and XZ54, respectively. Conclusively, this study adds further evidence to support the concept that Tibetan wild barley genotypes that utilize K efficiently could serve as a valuable genetic resource for the provision of genes for improved K metabolism in addition to those for combating drought stress, thereby enabling the development of elite barley lines better tolerant of abiotic stresses.

Genes Associated with the Flax Plant Type (Oil or Fiber) Identified Based on Genome and Transcriptome Sequencing Data

As a result of the breeding process, there are two main types of flax (Linum usitatissimum L.) plants. Linseed is used for obtaining seeds, while fiber flax is used for fiber production. We aimed to identify the genes associated with the flax plant type, which could be important for the formation of agronomically valuable traits. A search for polymorphisms was performed in genes involved in the biosynthesis of cell wall components, lignans, fatty acids, and ion transport based on genome sequencing data for 191 flax varieties. For 143 of the 424 studied genes (4CL, C3'H, C4H, CAD, CCR, CCoAOMT, COMT, F5H, HCT, PAL, CTL, BGAL, ABC, HMA, DIR, PLR, UGT, TUB, CESA, RGL, FAD, SAD, and ACT families), one or more polymorphisms had a strong correlation with the flax type. Based on the transcriptome sequencing data, we evaluated the expression levels for each flax type-associated gene in a wide range of tissues and suggested genes that are important for the formation of linseed or fiber flax traits. Such genes were probably subjected to the selection press and can determine not only the traits of seeds and stems but also the characteristics of the root system or resistance to stresses at a particular stage of development, which indirectly affects the ability of flax plants to produce seeds or fiber.

Transcriptomic profiling of susceptible and resistant flax seedlings after Fusarium oxysporum lini infection

In this study transcriptome was analyzed on two fibrous varieties of flax: the susceptible Regina and the resistant Nike. The experiment was carried out on 2-week-old seedlings, because in this phase of development flax is the most susceptible to infection. We analyzed the whole seedlings, which allowed us to recognize the systemic response of the plants to the infection. We decided to analyze two time points: 24h and 48h, because our goal was to learn the mechanisms activated in the initial stages of infection, these points were selected based on the previous analysis of chitinase gene expression, whose increase in time of Fusarium oxysporum lini infection has been repeatedly confirmed both in the case of flax and other plant species. The results show that although qualitatively the responses of the two varieties are similar, it is the degree of the response that plays the role in the differences of their resistance to F. oxysporum.

Integrated Proteomic and Metabolomic Profiling of Phytophthora cinnamomi Attack on Sweet Chestnut (Castanea sativa) Reveals Distinct Molecular Reprogramming Proximal to the Infection Site and Away from It

Phytophthora cinnamomi is one of the most invasive tree pathogens that devastates wild and cultivated forests. Due to its wide host range, knowledge of the infection process at the molecular level is lacking for most of its tree hosts. To expand the repertoire of studied Phytophthora-woody plant interactions and identify molecular mechanisms that can facilitate discovery of novel ways to control its spread and damaging effects, we focused on the interaction between P. cinnamomi and sweet chestnut (Castanea sativa), an economically important tree for the wood processing industry. By using a combination of proteomics, metabolomics, and targeted hormonal analysis, we mapped the effects of P. cinnamomi attack on stem tissues immediately bordering the infection site and away from it. P. cinnamomi led to a massive reprogramming of the chestnut proteome and accumulation of the stress-related hormones salicylic acid (SA) and jasmonic acid (JA), indicating that stem inoculation can be used as an easily accessible model system to identify novel molecular players in P. cinnamomi pathogenicity.

Characterization of Camptotheca acuminata 10-hydroxygeraniol oxidoreductase and iridoid synthase and their application in biological preparation of nepetalactol in Escherichia coli featuring NADP+ - NADPH cofactors recycling

Nepetalactol, an iridoid with four chiral carbons, is a crucial component of aphid sex pheromones that have been employed with great success to control the insect-related diseases. Despite of agricultural usage as end products, iridoids are fundamental biosynthetic intermediates for pharmaceutically important monoterpenoid indole alkaloids such as camptothecin (CAM) and vinca alkaloids. Herein we characterized 10-hydroxygeraniol oxidoreductase (10HGO) and iridoid synthase (IS) from Camptotheca acuminata, a CAM-producing plant, and reported their application in biological preparation of nepetalactol. Ca10HGO and CaIS were respectively cloned from C. acuminata, overexpressed in Escherichia coli, and purified to homogeneity. Ca10HGO catalyzes the oxidation of 10-hydroxygeraniol into 10-oxogeranial, in which NADP⁺ was reduced to NADPH. CaIS catalyzes nepetalactol formation from 10-oxogeranial using NADPH cofactor. The net outcome of the two reactions generate nepetalactol from 10-hydroxygeraniol efficiently, indicating NADP⁺ - NADPH recycling. Ca10HGO and CaIS were co-overexpressed in E. coli under optimized fermentation conditions to prepare cell-based catalysts that catalyze the conversion of 10-hydroxygeraniol into nepetalactol. The present work shows the enzymatic conversion of 10-hydroxygeraniol into nepetalactol involved in CAM biosynthesis. Co-overexpression of Ca10HGO and CaIS in E. coli is an alternative valuable cell-based biotransformation process with regenerating recycling of NADP⁺ - NADPH cofactors for nepetalactol preparation.

Soil enzyme response to bisphenol F contamination in the soil bioaugmented using bacterial and mould fungal consortium

The concept of the study resulted from the lack of accurate data on the toxicity of bisphenol F (BPF) coinciding with the need for immediate changes in the global economic policy eliminating the effects of environmental contamination with bisphenol A (BPA). The aim of the experiment was to determine the scale of the previously unstudied inhibitory effect of BPF on soil biochemical activity. To this end, in a soil subjected to increasing BPF pressure at three contamination levels of 0, 5, 50 and 500 mg BPF kg^-1 DM, responses of soil enzymes, dehydrogenases, catalase, urease, acid phosphatase, alkaline phosphatase, arylsulphatase and β-glucosidase, were examined. Moreover, the study suggested a potentially effective way of biostimulating the soil by means of bioaugmentation with a consortium of four bacterial species: Pseudomonas umsongensis, Bacillus mycoides, Bacillus weihenstephanensis and Bacillus subtilis, and the following fungal species: Mucor circinelloides, Penicillium daleae, Penicillium chrysogenum and Aspergillus niger. It was found that BPF was a controversial BPA analogue due to the fact that it contributed to the inhibition of all the enzyme activities. Dehydrogenases proved to be the most sensitive to bisphenol contamination of the soil. The addition of 5 mg BPF kg^-1 DM of soil triggered an escalation of the inhibition comparable to that for the other enzymes only after exposing them to the effects of 50 and 500 mg BPF kg^-1 DM of soil. Moreover, BPF generated low activity of urease, acid phosphatase, alkaline phosphatase and β-glucosidase. Bacterial inoculum increased the activity of urease, β-glucosidase, catalase and alkaline phosphatase. Seventy-six percent of BPF underwent biodegradation during the 5 days of the study.

The cinnamyl alcohol dehydrogenase gene family is involved in the response to Fusarium oxysporum in resistant and susceptible flax genotypes

Flax (Linum usitatissimum L.) is used for the production of textile, oils, pharmaceuticals, and composite materials. Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. lini, is a very harmful disease that reduces flax production. Flax cultivars that are resistant to Fusarium wilt have been developed, and the genes that are involved in the host response to F. oxysporum have been identified. However, the mechanisms underlying resistance to this pathogen remain unclear. In the present study, we used transcriptome sequencing data obtained from susceptible and resistant flax genotypes grown under control conditions or F. oxysporum infection. Approximately 250 million reads, generated with an Illumina NextSeq instrument, were analyzed. After filtering to exclude the F. oxysporum transcriptome, the remaining reads were mapped to the L. usitatissimum genome and quantified. Then, the expression levels of cinnamyl alcohol dehydrogenase (CAD) family genes, which are known to be involved in the response to F. oxysporum, were evaluated in resistant and susceptible flax genotypes. Expression alterations in response to the pathogen were detected for all 13 examined CAD genes. The most significant differences in expression between control and infected plants were observed for CAD1B, CAD4A, CAD5A, and CAD5B, with strong upregulation of CAD1B, CAD5A, and CAD5B and strong downregulation of CAD4A. When plants were grown under the same conditions, the expression levels were similar in all studied flax genotypes for most CAD genes, and statistically significant differences in expression between resistant and susceptible genotypes were only observed for CAD1A. Our study indicates the strong involvement of CAD genes in flax response to F. oxysporum but brings no evidence of their role as resistance gene candidates. These findings contribute to the understanding of the mechanisms underlying the response of flax to F. oxysporum infection and the role of CAD genes in stress resistance.

Cold stress affects cell wall deposition and growth pattern in tobacco pollen tubes

Cold is an abiotic stress seriously threatening crop productivity by decreasing biomass production. The pollen tube is a target of cold stress, but also a useful model to address questions on cell wall biosynthesis. We here provide (immuno)cytological data relative to the impact of cold on the pollen tube cell wall. We clearly show that the growth pattern is severely affected by the stress, since the typical pulsed-growth mechanism accompanied by the periodic deposition of pectin rings is absent/severely reduced. Additionally, pectins and cellulose accumulate in bulges provoked by the stress, while callose, which colocalizes with pectins in the periodic rings formed during pulsed growth, accumulates randomly in the stressed samples. The altered distribution of the cell wall components is accompanied by differences in the localization of glucan synthases: cellulose synthase shows a more diffuse localization, while callose synthase shows a more frequent cytoplasmic accumulation, thereby denoting a failure in plasma membrane insertion. The cell wall observations are complemented by the analysis of intracellular Ca2+, pH and reactive oxygen species (ROS): while in the case of pH no major differences are observed, a less focused Ca2+ and ROS gradients are present in the stressed samples. The standard oscillatory growth of pollen tubes is recovered by transient changes of turgor pressure induced by hypoosmotic media. Overall our data contribute to the understanding of the impact that cold stress has on the normal development of the pollen tube and unveil the cell wall-related aberrant features accompanying the observed alterations.

Early development of apoplastic barriers and molecular mechanisms in juvenile maize roots in response to La2O3 nanoparticles

The increasing occurrence of engineered nanoparticles (NPs) in soils may decrease water uptake in crops, followed by lower crop yield and quality. As one of the most common rare earth oxide NPs, lanthanum oxide (La₂O₃) NPs may inhibit the relative expressions of aquaporin genes, thus reduce water uptake. In the present study, maize plants were exposed to different La₂O₃ NPs concentrations (0, 5, 50 mg L^-1) for 72 h and 144 h right after the first leaf extended completely. Our results revealed that water uptake was reduced by La₂O₃ NPs through accelerating the development of apoplastic barriers in maize roots. The level of abscisic acid, determined by using ultra high performance liquid chromatography-tandem mass spectrometry, was increased upon La₂O₃ NPs exposure. Furthermore, ZmPAL, ZmCCR2 and ZmCAD6, the core genes specific for biosynthesis of lignin, were up-regulated by 3-13 fold in roots exposed to 50 mg L^-1 La₂O₃ NPs. However, ZmF5H was suppressed, indicating that lignin with S units could be excluded for the formed lignin in apoplastic barriers upon La₂O₃ NPs exposure. The level of essential component of apoplastic barriers - lignin was increased by 1.5-fold. The early development of apoplastic barriers was observed, and stomatal conductance and transpiration rate of La₂O₃ NPs-treated plants were significantly decreased by 63%-83% and 42%-86%, respectively, as compared to the control. The lignin enriched apoplastic barriers in juvenile maize thus led to the reduction of water uptake, subsequently causing significant growth inhibition. This is the first study to show early development of root apoplastic barriers upon La₂O₃ NPs exposure. This study will help us better understand the function of apoplastic barriers in roots in response to NPs, further providing fundamental knowledge to develop safer and more efficient agricultural nanotechnology.

Inoculated Clitoria ternatea with Bacillus cereus ERBP for enhancing gaseous ethylbenzene phytoremediation: Plant metabolites and expression of ethylbenzene degradation genes

Air pollutants especially polyaromatic hydrocarbons pose countless threats to the environment. This issue demands for an effective phytoremediation technology. In this study we report the beneficial interactions of Clitoria ternatea and its plant growth promoting endophytic bacteria Bacillus cereus ERBP by inoculating it for the remediation of 5 ppm airborne ethylbenzene (EB). The percentage efficiency for ethylbenzene removal among B. cereus ERBP inoculated and non-inoculated sterile and natural C. ternatea has also been determined. The inoculation of B. cereus ERBP has significantly increased EB removal efficiency of both sterile and natural C. ternatea. The inoculated natural C. ternatea seedlings showed 100% removal efficiency within 84 h for the aforementioned pollutant compared with the sterile inoculated C. ternatea seedlings (108 h). The degradation of EB by C. ternatea seedlings with and without B. cereus ERBP was assessed by measuring the intermediates of EB including 1-phenylethanol, acetophenon, benzaldehyde and benzoic acid. In addition, cytochrome P450s monooxygenase (CYP83D1) and dehydrogenases (LOC100783159) involved in the oxidation of hydrocarbons are well reported for their bio catalytic activities under xenobiotic stress conditions. Hence, the co-effect of the native endophyte B. cereus ERBP inoculation and EB exposure on the expression level of CYP83D1 and dehydrogenase were also determined. The targeted genes CYP83D1and dehydrogenases have shown an increased expression level under the 5 ppm of EB exposure enabling C. ternatea to withstand and remediate the pollutant.