The Maltase Involved in Starch Metabolism in Barley Endosperm Is Encoded by a Single Gene

Insights into the Molecular Basis of Huanglongbing Tolerance in Persian Lime (Citrus latifolia Tan.) through a Transcriptomic Approach

Huanglongbing (HLB) is a vascular disease of Citrus caused by three species of the α-proteobacteria "Candidatus Liberibacter", with "Candidatus Liberibacter asiaticus" (CLas) being the most widespread and the one causing significant economic losses in citrus-producing regions worldwide. However, Persian lime (Citrus latifolia Tanaka) has shown tolerance to the disease. To understand the molecular mechanisms of this tolerance, transcriptomic analysis of HLB was performed using asymptomatic and symptomatic leaves. RNA-Seq analysis revealed 652 differentially expressed genes (DEGs) in response to CLas infection, of which 457 were upregulated and 195 were downregulated. KEGG analysis revealed that after CLas infection, some DEGs were present in the plant-pathogen interaction and in the starch and sucrose metabolism pathways. DEGs present in the plant-pathogen interaction pathway suggests that tolerance against HLB in Persian lime could be mediated, at least partly, by the ClRSP2 and ClHSP90 genes. Previous reports documented that RSP2 and HSP90 showed low expression in susceptible citrus genotypes. Regarding the starch and sucrose metabolism pathways, some genes were identified as being related to the imbalance of starch accumulation. On the other hand, eight biotic stress-related genes were selected for further RT-qPCR analysis to validate our results. RT-qPCR results confirmed that symptomatic HLB leaves had high relative expression levels of the ClPR1, ClNFP, ClDR27, and ClSRK genes, whereas the ClHSL1, ClRPP13, ClPDR1, and ClNAC genes were expressed at lower levels than those from HLB asymptomatic leaves. Taken together, the present transcriptomic analysis contributes to the understanding of the CLas-Persian lime interaction in its natural environment and may set the basis for developing strategies for the integrated management of this important Citrus disease through the identification of blanks for genetic improvement.

Changes in key life-history traits and transcriptome regulations of marine rotifer Brachionus plicatilis in eliminating harmful algae Phaeocystis

Rotifers have great potential in controlling the harmful algae Phaeocystis blooms that frequently occur in coastal waters. To evaluate the effects of harmful algae on the key life-history traits of rotifer in eliminating Phaeocystis and reveal the underlying mechanism of these effects, we fed Brachionus plicatilis with Chlorella vulgaris and Phaeocystis globosa respectively, recorded the key life-history traits, and conducted transcriptomic analysis. Results showed that the rotifers feeding on P. globosa significantly decreased total offspring but obviously prolonged lifespan compared to those feeding on C. vulgaris, indicating that there was a trade-off between the reproduction and lifespan of rotifers feeding on algae with different nutrient contents. Nevertheless, rotifers can completely eliminate the population of P. globosa. The changes in the reproduction and lifespan of rotifers are highly correlated with algal key nutrition and the expression of some related genes. Transcriptomic analysis showed that the changes in the key life history traits of rotifers feeding on harmful algae are determined by regulating the expression of some key genes involved in the pathways of carbohydrate digestion and absorption, glycolysis, gluconeogenesis, unsaturated fatty acid biosynthesis, and environmental stress. Understanding the trade-off of the key life history traits of zooplankton in eliminating harmful algae from the underlying mechanism helps improve their application for controlling harmful algae.

A dominant mutation in β-AMYLASE1 disrupts nighttime control of starch degradation in Arabidopsis leaves

Arabidopsis (Arabidopsis thaliana) leaves possess a mechanism that couples the rate of nighttime starch degradation to the anticipated time of dawn, thus preventing premature exhaustion of starch and nighttime starvation. To shed light on the mechanism, we screened a mutagenized population of a starvation reporter line and isolated a mutant that starved prior to dawn. The mutant had accelerated starch degradation, and the rate was not adjusted to time of dawn. The mutation responsible led to a single amino acid change (S132N) in the starch degradation enzyme BETA-AMYLASE1 (BAM1; mutant allele named bam1-2D), resulting in a dominant, gain-of-function phenotype. Complete loss of BAM1 (in bam1-1) did not affect rates of starch degradation, while expression of BAM1(S132N) in bam1-1 recapitulated the accelerated starch degradation phenotype of bam1-2D. In vitro analysis of recombinant BAM1 and BAM1(S132N) proteins revealed no differences in kinetic or stability properties, but in leaf extracts, BAM1(S132N) apparently had a higher affinity than BAM1 for an established binding partner required for normal rates of starch degradation, LIKE SEX FOUR1 (LSF1). Genetic approaches showed that BAM1(S132N) itself is likely responsible for accelerated starch degradation in bam1-2D and that this activity requires LSF1. Analysis of plants expressing BAM1 with alanine or aspartate rather than serine at position 132 indicated that the gain-of-function phenotype is not related to phosphorylation status at this position. Our results strengthen the view that control of starch degradation in wild-type plants involves dynamic physical interactions of degradative enzymes and related proteins with a central role for complexes containing LSF1.

Description and functional analysis of the transcriptome from malting barley

The present study aimed to establish an early model of the malting barley transcriptome, which describes the expression of genes and their ontologies, identify the period during malting with the largest dynamic shift in gene expression for future investigation, and to determine the expression patterns of all starch degrading enzyme genes relevant to the malting and brewing industry. Large dynamic increases in gene expression occurred early in malting with differential expressed genes enriched for cell wall and starch hydrolases amongst many malting related categories. Twenty-five of forty starch degrading enzyme genes were differentially expressed in the malting barley transcriptome including eleven α-amylase genes, six β-amylase genes, three α-glucosidase genes, and all five starch debranching enzyme genes. Four new or novel α-amylase genes, one β-amylase gene (Bmy3), three α-glucosidase genes, and two isoamylase genes had appreciable expression that requires further exploration into their potential relevance to the malting and brewing industry.

An investigation of the pharmacological applications used for the Ancient Egyptian systemic model 'ra-ib' compared with modern Traditional Chinese Medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Ancient Egyptian texts only offer glimpses into their conceptual understandings of the inner-body and illness manifestation. Explanations of how prescribed materia medica were believed to work are rare and obscure, often resulting in modern approximations for ancient terminology such as 'ra-ib'-an ancient Egyptian classification predominantly translated as 'stomach'-leading to misunderstandings of historical texts, and therefore their use of pharmacology.

AIM OF THE STUDY

To investigate the ra-ib and the explanatory models of illness from the Egyptian perspective, and to explore the link between these and the prescribed selection of materia medica. To then compare the conceptual mechanics of these treatment strategies with those of another non-Western tradition-namely Traditional Chinese Medicine (TCM)-to provide further insight into potential conceptual frameworks.

MATERIALS AND METHODS

We conducted a case study of a unit of Ancient Egyptian texts focusing on the ra-ib. Totalling 34 prescriptions, the first stage lexicographically analysed the texts using cognitive linguistic and translation theories to produce our new understanding. This enabled our comparison of the mechanics of materia medica usage within these texts with those found in TCM outlined by the Pharmacopoeia of the Peoples Republic of Pharmacopeia of the People's Republic of China 2015 for the relevant ingredients.

RESULTS

the study demonstrated that-rather than denoting the organ 'stomach'-ra-ib instead constitutes a system running from the mouth, downward to the anus. This is best translated as 'inner thoroughfare', and changes the way in which we attempt to understand potential motivations in the selection of ingredients. By exploring common themes in the use of eleven securely translated ingredients from the Egyptian corpus and the Pharmacopoeia of the People's Republic of China-representing a modern traditional system which understands the body via a series of interconnected systems-we were able to highlight certain themes which might be 'universal' to system-based traditions; this provided new insights into the Egyptian motivations for treatment selection.

CONCLUSIONS

Having gained the ancient view of the body and illness, cultural comparisons are important for providing further potential insights and clarifications of a discontinued historical healing tradition. The new understanding of the ra-ib from our study greatly changes the way in which we understand the dynamics of Egyptian ethnopharmacological source material from this period.

Proteomics analysis of Cyclobalanopsis gilva provides new insights of low seed germination

A valuable plant, Cyclobalanopsis gilva, (C. gilva) has a low germination rate (below 50%) under its natural habitations. In order to examine the reasons for the low germination rate, the seeds of C. gilva (germinated and non-germinated) were evaluated using comparative proteomics analysis. A total of 3078 differentially abundant proteins (DAPs) were identified through a label-free method; most DAPs up-accumulated in germinated seeds were related to carbohydrates metabolism. Furthermore the proteins related to the signals, stress, and protein metabolism showed up-accumulation in germinated and no abundance or down-accumulation in non-germinated seeds. Enzyme activity of HK, PGK, PFK, and PK from glycolysis in SG-Control samples were 1.7-, 1.1-, 1.4-, and 1.3-times higher compared with those in control ones while CS, NAD-MDH, α-KGDH, and ICDH from the TCA cycle in SG-Control samples were 3, 1.1, 1.2, and 1.2 times higher than those in NG-Control ones. The β-amylase activity was 4-fold higher in successfully germinated seeds compared to non-germinated seeds. Interestingly, α-amylase did not show significant changes in protein abundance and enzyme activity among the three samples. The present findings reveal that unsuccessful germination of C. gilva seeds is due to lack of energy.

Molecular dynamics reveals insight into how N226P and H227Y mutations affect maltose binding in the active site of α-glucosidase II from European honeybee, Apis mellifera

European honeybee, Apis mellifera, produces α-glucosidase (HBGase) that catalyzes the cleavage of an α-glycosidic bond of the non-reducing end of polysaccharides and has potential applications for malt hydrolysis in brewing industry. Characterized by their substrate specificities, HBGases have three isoforms including HBGase II, which prefers maltose to sucrose as a substrate. Previous study found that the catalytic efficiency of maltose hydrolysis of N226P mutant of HBGase II was higher than that of the wild type (WT), and the catalytic efficiency of maltose hydrolysis of WT was higher than those of H227Y and N226P-H227Y mutants. We hypothesized that N226P mutation probably caused maltose to bind with better affinity and position/orientation for hydrolysis than WT, while H227Y and N226P-H227Y mutations caused maltose to bind with worse affinity and position/orientation for hydrolysis than WT. Using this hypothesis, we performed molecular dynamics on the catalytically competent binding conformations of maltose/WT, maltose/N226P, maltose/H227Y, and maltose/N226P-H227Y complexes to elucidate effects of N226P and H227Y mutations on maltose binding in HBGase II active site. Our results reasonably support this hypothesis because the N226P mutant had better binding affinity, higher number of important binding residues, strong and medium hydrogen bonds as well as shorter distance between atoms necessary for hydrolysis than WT, while the H227Y and N226P-H227Y mutants had worse binding affinities, lower number of important binding residues and strong hydrogen bonds as well as longer distances between atoms necessary for hydrolysis than WT. Moreover, results of binding free energy and hydrogen bond interaction of residue 227 support the role of H227 as a maltose preference residue, as proposed by previous studies. Our study provides important and novel insight into how N226P and H227Y mutations affect maltose binding in HBGase II active site. This knowledge could potentially be used to engineer HBGase II to improve its efficiency.

Genetic Analysis and Molecular Breeding Applications of Malting Quality QTLs in Barley

Malting quality is an important determinant of the value of barley grain used in malting and brewing. With recent sequencing and assembling of the barley genome, an increasing number of quantitative trait loci (QTLs) and genes related to malting quality have been identified and cloned, which lays a good molecular genetic basis for barley quality improvement. In this review, we describe the following indicators of malting quality: malt extract (ME), diastatic power (DP), kolbach index (KI), wort viscosity (VIS), free amino nitrogen (FAN) content, soluble protein (SP) content, wort β-glucan (WBG) content, and protein content (PC), and have list related QTLs/genes with high phenotypic variation in multiple populations or environments. Meanwhile, the correlations among the quality parameters and parts of significant indicators suitable for improvement are discussed based on nutrient composition and content required for high-quality malt, which will provide reference for molecular marker-assisted selection (MAS) of malting quality in barley.

A molecular perspective on starch metabolism in woody tissues

MAIN CONCLUSION

The elucidation of the molecular mechanisms of starch synthesis and mobilization in perennial woody tissues is of the utmost scientific and agricultural importance. Starch is the main carbohydrate reserve in plants and is fundamental in human nutrition and several industrial processes. In leaves, starch accumulated during the day is degraded throughout the night and the resulting sugars, glucose and maltose, are exported to the cytosol by the specialized transmembrane translocators pGT and MEX, respectively. Nevertheless, the degradation of the starch granule is a complex process not completely elucidated. While the mechanisms of starch mobilization during germination in the dead endosperm of cereal seeds are well described, the molecular and biochemical mechanisms involved in starch storage in the heterotrophic tissues of woody plants and its utilization in spring and winter are still puzzling. It is known that some biochemical steps of starch synthesis are conserved in heterotrophic tissues and in the leaves, but some aspects are particular to sink organs. From an agronomic standpoint, the knowledge on starch storage and mobilization in woody tissues is pivotal to understand (and to optimize) some common practices in the field that modify source-sink relationships, such as pruning and defoliation. Soluble sugars resulting from starch are also pivotal to cold adaptation, and in several fruits, such as banana and kiwifruit, starch may provide soluble sugars during ripening. In this review, we explore the recent advances on the molecular mechanisms and regulations involved in starch synthesis and mobilization, with a focus on perennial woody tissues.

Comparative expression analysis of starch degrading genes between dormant and non-dormant wheat seeds

To gain insights into the molecular basis of starch degradation in wheat seeds with respect to dormancy maintenance and release, this study compared the expression of starch degrading genes between dormant and after-ripened seeds in both dry and imbibed states. Furthermore, the study examined the effect of ABA on the expression of starch degrading genes during imbibition of non-dormant seeds. Release of dormancy due to after-ripening led to the upregulation of specific genes encoding α-amylase and α-glucosidase during imbibition while dormancy maintenance is associated with repression of these genes. It appears from our result that ABA delays the germination of wheat seeds at least partly through repression of the starch degrading genes.

High-Throughput In Vitro Screening for Inhibitors of Cereal α-Glucosidase

The hydrolysis of starch is a key step in plant germination, which also has relevance in the malting and brewing processes for beer and spirit production. Gaps in knowledge about this metabolic process exist that cannot easily be addressed using traditional genetic techniques, due to functional redundancy in many of the enzyme activities required for alpha-glucan metabolism in cereal crop species. Chemical inhibitors provide opportunities to probe the role of carbohydrate-active enzymes and the phenotypes associated with inhibition of specific enzymes. Iminosugars are the largest group of carbohydrate-active enzyme inhibitors and represent an underused resource for the dissection of plant carbohydrate metabolism. Herein we report a method for carrying out a reverse chemical genetic screen on α-glucosidase, the enzyme that catalyzes the final step in starch degradation during plant germination, namely the hydrolysis of maltose to release glucose. This chapter outlines the use of a high-throughput screen of small molecules for inhibition of α-glucosidase using a colorimetric assay which involves the substrate p-nitrophenyl α-D-glucopyranoside. Identified inhibitors can be further utilized in phenotypic screens to probe the roles played by amylolytic enzymes. Furthermore this 96-well plate-based method can be adapted to assay exo-glycosidase activities involved in other aspects of carbohydrate metabolism.

Cell wall degradation is required for normal starch mobilisation in barley endosperm

Starch degradation in barley endosperm provides carbon for early seedling growth, but the control of this process is poorly understood. We investigated whether endosperm cell wall degradation is an important determinant of the rate of starch degradation. We identified iminosugar inhibitors of enzymes that degrade the cell wall component arabinoxylan. The iminosugar 1,4-dideoxy-1, 4-imino-l-arabinitol (LAB) inhibits arabinoxylan arabinofuranohydrolase (AXAH) but does not inhibit the main starch-degrading enzymes α- and β-amylase and limit dextrinase. AXAH activity in the endosperm appears soon after the onset of germination and resides in dimers putatively containing two isoforms, AXAH1 and AXAH2. Upon grain imbibition, mobilisation of arabinoxylan and starch spreads across the endosperm from the aleurone towards the crease. The front of arabinoxylan degradation precedes that of starch degradation. Incubation of grains with LAB decreases the rate of loss of both arabinoxylan and starch, and retards the spread of both degradation processes across the endosperm. We propose that starch degradation in the endosperm is dependent on cell wall degradation, which permeabilises the walls and thus permits rapid diffusion of amylolytic enzymes. AXAH may be of particular importance in this respect. These results provide new insights into the mobilization of endosperm reserves to support early seedling growth.