Sucrose Storage Research Articles

Double blocking of carbon metabolism causes a large increase of Calvin-Benson cycle compounds in cyanobacteria.

Carbon-flow-regulator A (CfrA) adapts carbon flux to nitrogen conditions in nondiazotrophic cyanobacteria. Under nitrogen deficiency, CfrA leads to the storage of excess carbon, which cannot combine with nitrogen, mainly as glycogen. cfrA overexpression from the arsenite-inducible, nitrogen-independent ParsB promoter allows analysis of the metabolic effects of CfrA accumulation. Considering that the main consequence of cfrA overexpression is glycogen accumulation, we examined carbon distribution in response to cfrA expression in Synechocystis sp. PCC 6803 strains impaired in synthesizing this polymer. We carried out a comparative phenotypic analysis to evaluate cfrA overexpression in the wild-type strain and in a mutant of ADP-glucose pyrophosphorylase (ΔglgC), which is unable to synthesize glycogen. The accumulation of CfrA in the wild-type background caused a photosynthetic readjustment although growth was not affected. However, in a ΔglgC strain, growth decreased depending on CfrA accumulation and photosynthesis was severely affected. An elemental analysis of the H, C, and N content of cells revealed that cfrA expression in the wild-type caused an increase in the C/N ratio, due to decreased nitrogen assimilation. Metabolomic study indicated that these cells store sucrose and glycosylglycerol, in addition to the previously described glycogen accumulation. However, cells deficient in glycogen synthesis accumulated large amounts of Calvin-Benson cycle intermediates as cfrA was expressed. These cells also showed increased levels of some amino acids, mainly alanine, serine, valine, isoleucine, and leucine. The findings suggest that by controlling cfrA expression, in different conditions and strains, we could change the distribution of fixed carbon, with potential biotechnological benefits.

Brassinosteroids alleviates wheat floret degeneration under low nitrogen stress by promoting the distribution of sucrose from stems to spikes

The trade-off between yield and environmental effects caused by nitrogen fertilizer application is an important issue in wheat production. A reduction in fertile florets is one of the main reasons for decreased yield under low nitrogen application rate. Brassinosteroids (BRs) have been found to play a role in nitrogen-induced rice spikelet degeneration. However, whether BRs play a role in wheat floret development and the mechanisms involved are not clear. Therefore, different nitrogen gradient experiment and exogenous spraying experiment were conducted to investigate the role and mechanism of BRs in wheat floret development under low nitrogen stress. The results showed that as the nitrogen application decreased, the endogenous BRs content of spikes decreased, photosynthesis weakened, and total carbon, soluble sugar and starch of spikes decreased, leading to a reduction in the number of fertile florets. Under low nitrogen stress, exogenous spraying of 24-epibrassinolide promoted photosynthesis, stimulated stem fructan hydrolysis and the utilization and storage of sucrose in spikes, directing more carbohydrates to the spikes and increasing the number of fertile florets. In conclusion, BRs mediate the effects of nitrogen fertilizer on wheat floret development, and under low nitrogen stress, foliar spraying of 24-epibrassinolide promotes the flow of carbohydrates from the stem to the spikes, alleviating wheat floret degeneration.

Transcriptome analysis of sugarcane reveals differential switching of major defense signaling pathways in response to Sporisorium scitamineum isolates with varying virulent attributes.

Sugarcane smut caused by the basidiomycetous fungus Sporisorium scitamineum is one of the most devastating diseases that affect sugarcane production, globally. At present, the most practical and effective management strategy for the disease is the cultivation of resistant cultivars. In this connection, a detailed understanding of the host's defense mechanism in response to smut isolates with varying degrees of virulence at the molecular level would facilitate the development of reliable and durable smut-resistant sugarcane varieties. Hence, in this study, a comparative whole transcriptome analysis was performed employing Illumina RNA-seq in the smut susceptible cultivar Co 97009 inoculated with two distinct S. scitamineum isolates, Ss97009 (high-virulent) and SsV89101 (low-virulent) during the early phases of infection (2 dpi and 5 dpi) and at the phase of sporogenesis (whip emergence) (60 dpi). Though the differential gene expression profiling identified significant transcriptional changes during the early phase of infection in response to both the isolates, the number of differentially expressed genes (DEGs) were more abundant at 60 dpi during interaction with the high virulent isolate Ss97009, as compared to the low virulent isolate SsV89101. Functional analysis of these DEGs revealed that a majority of them were associated with hormone signaling and the synthesis of defense-related metabolites, suggesting a complex network of defense mechanisms is being operated in response to specific isolates of the smut pathogen. For instance, up-regulation of hormone-related genes, transcription factors, and flavonoid biosynthesis pathway genes was observed in response to both the isolates in the early phase of interaction. In comparison to early phases of infection, only a few pathogenesis-related proteins were up-regulated at 60 dpi in response to Ss97009, which might have rendered the host susceptible to infection. Strikingly, few other carbohydrate metabolism-associated genes like invertases were up-regulated in Ss97009 inoculated plants during the whip emergence stage, representing a shift from sucrose storage to smut symptoms. Altogether, this study established the major switching of defense signaling pathways in response to S. scitamineum isolates with different virulence attributes and provided novel insights into the molecular mechanisms of sugarcane-smut interaction.

How foraging preference and activity level of bumble bees contribute to colony flexibility under resource demand

Groups of cooperative organisms, including humans, benefit from the contributions of both specialist and generalist individuals. Group responses to resource or task demand emerge from the specific actions of individuals within the group. Bumble bee colonies need to respond to resource demands for both pollen and nectar for colony growth and reproduction. Bumble bee workers have been shown to display differences in foraging preferences for these essential resources and in activity level. This study investigated the responses of Bombus terrestris individuals to resource demand by subjecting colonies to different pollen and sucrose storage scenarios, considering their individual foraging preferences and activity levels. The sucrose sensitivity and olfactory learning ability of individuals were then compared along a spectrum of foraging preference (between pollen and sucrose foraging) using the proboscis extension reflex paradigm. When sucrose was in demand, individuals with a preference for sucrose showed the largest upregulation in foraging bouts. Individual preference for pollen and activity level correlated with the upregulation of foraging bouts when pollen was in demand. This study detected no relationship between body size, sucrose preference and worker sucrose sensitivity or olfactory learning ability, tested with proboscis extension reflex conditioning. This study highlights the potential value of foraging preferences in bumble bee colonies but also the flexibility these colonies have with a small foraging workforce. • Bumble bees with high sucrose preference upregulate to fill sucrose demands. • Pollen preference and individual activity level predict upregulation in pollen demand. • Body size and sucrose preference do not predict worker sucrose sensitivity. • Body size and sucrose preference do not predict odour learning performance. • Workload is not evenly split between individuals.

Dynamics of carbon export from leaves as translocation affected by the coordination of carbohydrate availability in field strawberry

Carbon export from leaves as translocation is a result of plant coordination of leaf carbohydrate availability. Carbohydrate availability coordination is actively studied in model plants (Arabidopsis) under regulated conditions and can be optimized to increase productivity. However, in horticultural crops grown under field conditions, carbon export dynamics and coordination are poorly understood. The objective of this study was to analyze the dynamics of carbon export from leaves and the effects of carbohydrate availability coordination on these dynamics in strawberry grown under field conditions. Through three different day/night cycles, we measured leaf carbohydrate concentrations and photosynthetic rates and evaluated the dynamics of carbon export based on the leaf carbon balance. During the daytime, when carbon resources are almost entirely supplied by photosynthesis, strawberry leaves stored sucrose and starch. Starch synthesis was remarkable when sucrose concentration exceeded 150 mmol m−2, and the carbon export rate tended to increase. In the nighttime, when carbon resources are supplied by leaf sucrose and starch stored during the daytime, the starch concentrations decreased linearly and the carbon export rate was lower than the daytime level. These results indicate that in the daytime, the coordination of leaf carbohydrate availability for starch storage and carbon export was affected by leaf sucrose concentration, whereas, at night, it was regulated by leaf carbon storage levels at dusk rather than sucrose concentration. Thus, this study elucidates the basis of carbon export dynamics in strawberry leaves under field conditions, advancing our understanding of the role of leaf carbohydrates in translocation.

Identification of microRNAs involved in sucrose accumulation in sugarcane (Saccharum species hybrid)

The genetic improvement efforts in sugarcane are largely centered around increasing its sucrose accumulation potential. Sugarcane genotypes show variable regulation of genes involved in synthesis, accumulation, transport, storage and subsequent retention of sucrose. MicroRNAs (miRNAs), which are a class of small non-coding RNAs play a very important role in post-transcriptional regulation of genes. Very little has been reported on the miRNA-mediated regulation of sucrose accumulation in sugarcane. In this study, two sugarcane genotypes contrasting for sucrose content along with two extreme bulks from their F1 population were used to identify differentially expressed miRNAs which might play a regulatory role in sucrose accumulation. A total of 161 miRNAs were identified, of them, 23 were significantly differential for contrasting sucrose content. The target genes of the identified miRNAs were predicted and some of them were validated using transcriptome library-based gene expression levels. Nineteen differential miRNAs and six selected target genes were validated using quantitative PCR. The study revealed that miRNA might be involved in sucrose accumulation in sugarcane, not by directly targeting the sucrose metabolism genes but by targeted regulation of transcription factors (PCF8, GRFs, ARF, etc.), and genes involved in carbohydrate metabolism, vegetative to mature phase transition, stress response, ion transport, growth and developmental pathways in sugarcane like RAV6, calcium-dependent protein kinase, HSP20, diacylglycerol kinase, squamosa promoter binding protein, etc. This study identifies miRNA candidates involved in sucrose accumulation and enriches the small RNA inventory of sugarcane.

Metabolic Disturbance Induced by the Embryo Contributes to the Formation of Chalky Endosperm of a Notched-Belly Rice Mutant.

Grain chalkiness is a key quality trait of the rice grain, whereas its underlying mechanism is still not thoroughly understood because of the complex genetic and environmental interactions. We identified a notched-belly (NB) mutant that has a notched-line on the belly of grains. The line dissects the endosperm into two distinct parts, the upper translucent part, and the bottom chalky part in the vicinity of the embryo. Using this mutant, our previous studies clued the negative influence of embryo on the biochemical makeup of the endosperm, suggesting the need for the in-depth study of the embryo effect on the metabolome of developing endosperm. This study continued to use the NB mutant to evolve a novel comparison method to clarify the role of embryo in the formation of a chalky endosperm. Grain samples of the wild-type (WT) and NB were harvested at 10, 20, and 30 days after fertilization (DAF), and then divided into subsamples of the embryo, the upper endosperm, and the bottom endosperm. Using non-targeted metabolomics and whole-genome RNA sequencing (RNA-seq), a nearly complete catalog of expressed metabolites and genes was generated. Results showed that the embryo impaired the storage of sucrose, amino acid, starch, and storage proteins in the bottom endosperm of NB by enhancing the expression of sugar, amino acids, and peptide transporters, and declining the expression of starch, prolamin, and glutelin synthesis-related genes. Importantly, the competitive advantage of the developing embryo in extracting the nutrients from the endosperm, transformed the bottom endosperm into an “exhaustive source” by diverting the carbon (C) and nitrogen (N) metabolism from synthetic storage to secondary pathways, resulting in impaired filling of the bottom endosperm and subsequently the formation of chalky tissue. In summary, this study reveals that embryo-induced metabolic shift in the endosperm is associated with the occurrence of grain chalkiness, which is of relevance to the development of high-quality rice by balancing the embryo–endosperm interaction.

PROTOTYPE LAMPU PENERANGAN PERSAWAHAN OTOMATIS MENGGUNAKAN SOLAR CELL DAN SENSOR CAHAYA

Lampu merupakan salah satu komponen terpenting dalam penerangan di ruangan ataupun diluar ruangan. Lampu memberikan manfaat yang sangat besar khususnya pada malam hari. Penulis pada penelitian ini telah mengembangkan lampu penerangan otomatis yang diterapkan pada area persawahan, biasanya lampu otomatis ini hanya diterapkan pada sepanjang jalan raya. Dengan adanya lampu penerangan otomatis diarea persawahan ini dapat membantu petani saat musim panen tebu yang biasanya dilakukan sampai malam hari. Lampu penerangan persawahan ini tidak memakai sumber listrik PLN namun menggunakan energi matahari yang kemudian diubah menjadi energi listrik dengan bantuan solar cell. Suhu ideal pertumbuhan dan pembentukan sukrosa tebu berkisar antara 24°C-34°C dengan perbedaan suhu antara siang dan malam tidak lebih dari 10°C. Proses penyimpanan sukrosa ini paling efektif dan optimal pada suhu 15°C. Oleh sebab itu, tebu yang dipanen malam hari berpotensi lebih manis daripada tebu yangg dipanen pada siang hari. Hasil dari pengujian alat yang telah dilakukan oleh peneliti yaitu lampu dapat menyala dan mati secara otomatis dengan bantuan sensor LDR. Lampu led akan mati saat nilai sensor LDR lebih kecil dari 899, dan lampu led akan menyala jika nilai sensor LDR lebih besar dari 900. Solar cell dapat mengisi baterai Li-Ion (Lithium-Ion) berjumlah 1-4 buah. Waktu yang paling optimal untuk proses charging solar cell yaitu antara jam 09.00 – jam 15.00.

Type I H+-pyrophosphatase regulates the vacuolar storage of sucrose in citrus fruit.

The aim of this work was to evaluate the general role of the vacuolar pyrophosphatase proton pump (V-PPase) in sucrose accumulation in citrus species. First, three citrus V-PPase genes, designated CsVPP-1, CsVPP-2, and CsVPP-4, were identified in the citrus genome. CsVPP-1 and CsVPP-2 belonging to citrus type I V-PPase genes are targeted to the tonoplast, and CsVPP-4 belonging to citrus type II V-PPase genes is located in the Golgi bodies. Moreover, there was a significantly positive correlation between transcript levels of type I V-PPase genes and sucrose, rather than hexose, content in fruits of seven citrus cultivars. Drought and abscisic acid treatments significantly induced the CsVPP-1 and CsVPP-2 transcript levels, as well as the sucrose content. The overexpression of type I V-PPase genes significantly increased PPase activity, decreased pyrophosphate contents, and increased sucrose contents, whereas V-PPase inhibition produced the opposite effect in both citrus fruits and leaves. Furthermore, altering the expression levels of type I V-PPase genes significantly influenced the transcript levels of sucrose transporter genes. Taken together, this study demonstrated that CsVPP-1 and CsVPP-2 play key roles in sucrose storage in the vacuole by regulating pyrophosphate homeostasis, ultimately the sucrose biosynthesis and transcript levels of sucrose transport genes, providing a novel lead for engineering or breeding modified taste in citrus and other fruits.

Potassium-mediated regulation of sucrose metabolism and storage root formation in sweet potato

ABSTRACT A two-year field experiment was conducted to investigate the effects of potassium on sucrose metabolism in the root system and its relationship with storage root formation in sweetpotato. Edible varieties Yanshu 25 and Beijing 553 were treated with K2O at 0, 12, 24, or 36 g m−2, and the number and length of adventitious roots in early growth stage, sucrose and hexose contents, and related enzyme activity in potential storage roots, as well as the number of storage roots and yield at harvest, were analyzed. The results showed K significantly increased the average number of storage roots per plant and yield at harvest, compared to the control. The increases were highest in 24 g m−2 K2O treatment, they changed slightly and even decreased with more K2O. Further study revealed appropriate potassium rate significantly increased the number and length of adventitious roots in early storage root formation stage. It also increased the activities of vacuolar, cell-wall and cytosolic invertase, coinciding with decreased sucrose versus increased fructose and glucose contents in potential roots. As per statistical path analysis, fructose accumulation contributed the most to storage root formation, while, in turn, cytosolic invertase contributed the most to promoting sucrose degradation and fructose accumulation.

Rhythms of Transcription in Field-Grown Sugarcane Are Highly Organ Specific

Circadian clocks improve plant fitness in a rhythmic environment. As each cell has its own circadian clock, we hypothesized that sets of cells with different functions would have distinct rhythmic behaviour. To test this, we investigated whether different organs in field-grown sugarcane follow the same rhythms in transcription. We assayed the transcriptomes of three organs during a day: leaf, a source organ; internodes 1 and 2, sink organs focused on cell division and elongation; and internode 5, a sink organ focused on sucrose storage. The leaf had twice as many rhythmic transcripts (>68%) as internodes, and the rhythmic transcriptomes of the internodes were more like each other than to those of the leaves. Among the transcripts expressed in all organs, only 7.4% showed the same rhythmic pattern. Surprisingly, the central oscillators of these organs — the networks that generate circadian rhythms — had similar dynamics, albeit with different amplitudes. The differences in rhythmic transcriptomes probably arise from amplitude differences in tissue-specific circadian clocks and different sensitivities to environmental cues, highlighted by the sampling under field conditions. The vast differences suggest that we must study tissue-specific circadian clocks in order to understand how the circadian clock increases the fitness of the whole plant.

Unravelling Sugar Accumulation in Sugarcane (Saccharum spp.) Stalk: Recent Approaches

Sucrose accumulation in developing sugarcane (Saccharum officinarum) is accompanied by a continuous synthesis and cleavage of sucrose in the storage tissues. It is synthesized in source mature leaves and such assimilates stored in the form of sucrose in the stalks of sugarcane that provide 70% of world sugar. During the phloem transportation, sucrose is unloaded into the sink for metabolism and storage. Its accumulation in sugarcane stalks is affected by sucrose supply, metabolism and sink strength. Sucrose accumulation and carbohydrate metabolism in plant species depend upon activity of Sucrose Synthase (SuSy) enzyme. Fast growing tissues in sugarcane such as root apices, immature stem internodes, cells and tissue cultures usually have low sucrose and higher concentration of SAI (soluble acid invertase) which hydrolyses sucrose into glucose and fructose. The sugar yield needs its enhancement to meet the growing demand for sugar. The photosynthesis activity in source leaves decides the amount of sucrose to sink organs. Sucrose metabolism enzymes control sucrose content in sugarcane stalks. Sucrose accumulation is a complex physiological process controlled by network genes. Recent biochemical and molecular approaches have resolved the various developmental and molecular regulation mechanisms for sucrose accumulation in sugarcane. In this review, discussion have been focussed on molecular involved in sucrose metabolism, source-sink communication and storage, microarray analysis, expressed sequence tags (ESTs) studies, physiological and tissue-specific gene regulation that will help further researches to elucidate the regulatory networks of sucrose accumulation to breed high sugar content in sugarcane.

Colocalization of sucrose synthase expression and sucrose storage in the sugarbeet taproot indicates a potential role for sucrose catabolism in sucrose accumulation

Sucrose metabolism is believed to have a central role in promoting sink strength and sucrose storage in the sugarbeet taproot. How sucrose accumulation is increased by sucrose-degrading enzymes, however, is a paradox. To elucidate roles for sucrose-degrading activities in sucrose accumulation, relationships between the intercellular location of sucrose-catabolizing enzymes and sites of sucrose accumulation were determined in the sugarbeet taproot. Sucrose storage was evident in parenchyma cells of the outer cortex, rays, and rings of parenchyma tissue, but was absent in phloem, the vascular cambium, cells surrounding these tissues, or cells surrounding xylem. Sucrose synthase, which was primarily responsible for sucrose catabolism throughout the taproot, was expressed in similar cell and tissue types to those accumulating sucrose. Colocalization of sucrose synthase with sucrose accumulation, as well as sucrose synthase localization near the tonoplast, suggests a role for the enzyme in generating metabolic energy to fuel sucrose sequestration in the vacuole. Localization near the plasma membrane also suggests a role for sucrose synthase in supplying substrates for cell wall biosynthesis. By utilizing sucrose for ATP or cell wall biosynthesis, sucrose synthase likely maintains the source-to-sink sucrose gradient that drives sucrose transport into the root, thereby promoting sugarbeet root sink strength.

Changes in total free amino acids as quality biomarkers in cut gladiolus spikes as affected by pulsing and wet cold storage

This study aimed at evaluating and quantifying Total Free Amino acids (TFAA) as indicators of quality in cut Gladiolus grandiflorus L. cv. Fado as affected by pulsing with 600 ppm 8-hydroxyquinoline sulphate plus 5% sucrose and subsequent wet-cold storage durations of 0–5 days. Spectrophotometric and thin layer chromatography of dried petal amino acid analyses of open field grown Gladiolus at Horticulture Research and Teaching Field at egerton University, Kenya, were done. A two by six factorial experiment embedded in a completely randomized design with four replicates was adopted and data was analyzed using Proc GLM model in two way Anova. Means were separated by Tukey's test at 5% level of confidence. Values of TFAA and the vase life were significantly (P< 0.0001) affected by the pulsing and wet-cold storage treatments with consequent enhanced mean vase life (10.33 ± 0.21 days) and lowered (28.006 ± 0.006 μg/mg dw) mean TFAA compared with that of the control (4.75 ± 0.21 days; 36.496 ± 0.006, respectively). Petals predominantly displayed proline, lysine, leucine, isoleucine, glutamine, glycine and threonine, which could be alternative respiratory substrates or physiological signals. The results from this study will augment existing technologies in improvement of postharvest handling of Gladiolus.

Cloning, expression, and localization analysis of the sucrose transporter gene JcSUT4 in the biofuel plant Jatropha curcas

ABSTRACTSucrose transporters (SUTs) play an important role in regulating fruit growth and development in planta. The fruit of Jatropha curcas, an important tropical tree used as biofuel material, ripens rapidly after flowering. Here, a SUT gene JcSUT4 from J. curcas was cloned and analyzed. JcSUT4, encoding a protein of 500 amino acid residues, was a Type III SUT homolog by a phylogenetic analysis. A transient expression assay in protoplasts showed that JcSUT4 was mainly localized to the plasma membrane. Complementation of yeast sucrose uptake-deficient mutant strains revealed that JcSUT4 was capable of transporting sucrose. JcSUT4 was highly expressed in mature source leaves, as well as in fruits at 30 days after full bloom (DAFB), which was in accordance with the stages of fruit swelling and ripening. This work shows that JcSUT4 may participate in the fruit growth and development of J. curcas, particularly be involved in sucrose storage in fruit. Taken together, our results provide new insights into the molecular mechanisms underpinning of SUTs in Jatropha.

Impact of Temperature and Humidity on Sugar Recovery in Uttar Pradesh

Sugarcane is one of the main cash crops in India, and around 42 lakh farmers directly or indirectly depend on this crop which occupies 23 lakh hectare areas in Uttar Pradesh. Temperature and humidity plays an important role in sucrose synthesis and accumulation in C4 plant such as sugarcane. In C4 plants, formation of phosphoenolpyruvate carboxykinase is sensitive to low temperatures. During low temperature and high humidity, there is an increase in juice acidity, probably due to the formation of organic acids, which are formed by the conversion of stored sucrose in the stalk. This conversion is reversed when the atmospheric temperature becomes favourable for sucrose accumulation. In subtropical India, sugarcane crop experiences varied weather conditions during its growth and development. The crushing season of sugar mills of Uttar Pradesh (UP), India, starts from November and continues till the April/May. However, due to immaturity of plant crop, sugar industries avoid starting their crushing season in November, but due to pressure of cane quantity as well as sowing time of wheat crop during this time by the farmers, sugar mills are forced to start their crushing season in November. The area of early varieties in UP was about 35% during crushing season 2015–2016, and sugar recovery was 10.62%; however, area of early-maturing high sugared varieties in UP increased up to 53% during crushing season 2016–2017, but sugar recovery was at par, i.e., 10.61%. Seeing the recovery data of different crushing seasons, a study was conducted at UPCSR Shahjahanpur to evaluate the impact of climatic conditions on sugar recovery percentage. Totally, 15 sugar mills were selected for this study from east, central and west zones of UP and their recoveries were observed and correlated with temperature and humidity. The study revealed that in spite of 18% increase in the area of high yielding, high sugared varieties in the state, which could have increased the sugar recovery, the low-temperature and high-humidity conditions during the start of the crushing season 2016–2017, affected the sugar accumulation in sugarcane, resulting into the average recovery which was at par as the previous year.

The prediction of moisture adsorption isotherm for sucrose powder in Côte d’Ivoire

Moisture sorption isotherms play an essential role in preservation and storage of dehydrated food. To study the behavior of sucrose, it’s moisture adsorption isotherm was investigated using the static gravimetrique method at laboratory temperature (29 ±1°C) in a water activity range (aw) of 0.07-0.97. The results showed that the equilibrium moisture content of sucrose increase substantially above aw = 0.6. The moisture adsorption isotherm was sigmoid in shap, showing a type III BET isotherm. The data obtained were fitted to several models including two-parameter (BET, Hasley, Kuhn and Oswin), three parameter (GAB). A non-linear least square regression analysis was used to evaluate the models constants. The GAB model best fitted the experimental data in the wide range of water activity. The best fitted equation provide a sound basis for futur work on the drying and storage of sucrose. The accurate moisture content and the stability profile of sucrose were determined. The results of determination show that sucrose powder was stable below 7.7% RH at 29°C. The content of water adsorbed in the monomolecular layer was calculated (GAB Xm=0.950 g H2O/100 g solids; BET Xm= 1.072 g H2O/100 g solids).

Cell wall metabolism and hexose allocation contribute to biomass accumulation in high yielding extreme segregants of a Saccharum interspecific F2 population

BackgroundSugarcane is an emerging dual-purpose biofuel crop for energy and sugar production, owing to its rapid growth rate, high sucrose storage in the stems, and high lignocellulosic yield. It has the highest biomass production reaching 1.9 billion tonnes in 2014 worldwide.ResultsTo improve sugarcane biomass accumulation, we developed an interspecific cross between Saccharum officinarum ‘LA Purple’ and Saccharum robustum ‘MOL5829’. Selected F1 individuals were self-pollinated to generate a transgressive F2 population with a wide range of biomass yield. Leaf and stem internodes of fourteen high biomass and eight low biomass F2 extreme segregants were used for RNA-seq to decipher the molecular mechanism of rapid plant growth and dry weight accumulation. Gene Ontology terms involved in cell wall metabolism and carbohydrate catabolism were enriched among 3274 differentially expressed genes between high and low biomass groups. Up-regulation of cellulose metabolism, pectin degradation and lignin biosynthesis genes were observed in the high biomass group, in conjunction with higher transcript levels of callose metabolic genes and the cell wall loosening enzyme expansin. Furthermore, UDP-glucose biosynthesis and sucrose conversion genes were differentially expressed between the two groups. A positive correlation between stem glucose, but not sucrose, levels and dry weight was detected.ConclusionsWe thus postulated that the high biomass sugarcane plants rapidly convert sucrose to UDP-glucose, which is the building block of cell wall polymers and callose, in order to maintain the rapid plant growth. The gene interaction of cell wall metabolism, hexose allocation and cell division contributes to biomass yield.

Brachypodium as an experimental system for the study of stem parenchyma biology in grasses.

Stem parenchyma is a major cell type that serves key metabolic functions for the plant especially in large grasses, such as sugarcane and sweet sorghum, where it serves to store sucrose or other products of photosynthesis. It is therefore desirable to understand the metabolism of this cell type as well as the mechanisms by which it provides its function for the rest of the plant. Ultimately, this information can be used to selectively manipulate this cell type in a controlled manner to achieve crop improvement. In this study, we show that Brachypodium distachyon is a useful model system for stem pith parenchyma biology. Brachypodium can be grown under condition where it resembles the growth patterns of important crops in that it produces large amounts of stem material with the lower leaves senescing and with significant stores of photosynthate located in the stem parenchyma cell types. We further characterize stem plastid morphology as a function of tissue types, as this organelle is central for a number of metabolic pathways, and quantify gene expression for the four main classes of starch biosynthetic genes. Notably, we find several of these genes differentially regulated between stem and leaf. These studies show, consistent with other grasses, that the stem functions as a specialized storage compartment in Brachypodium.

Structure, phylogeny, allelic haplotypes and expression of sucrose transporter gene families in Saccharum.

BackgroundSugarcane is an economically important crop contributing to about 80 % of the world sugar production. Increasing efforts in molecular biological studies have been performed for improving the sugar yield and other relevant important agronomic traits. However, due to sugarcane’s complicated genomes, it is still challenging to study the genetic basis of traits, such as sucrose accumulation. Sucrose transporters (SUTs) are critical for both phloem loading in source tissue and sucrose uptaking in sink tissue, and are considered to be the control points for regulating sucrose storage. However, no genomic study for sugarcane sucrose transporter (SsSUT) families has been reported up to date.ResultsBy using comparative genomics and bacterial artificial chromosomes (BACs), six SUT genes were identified and characterized in S. spontaenum. Phylogenetic analyses revealed that the two pairs SsSUTs (SsSUT1/SsSUT3 and SsSUT5/SsSUT6) could be clustered together into two separate monocot specific SUT groups, while SsSUT2 and SsSUT4 were separated into the other two groups, with members from both dicot and monocot species. Gene structure comparison demonstrated that the number and position of exons/introns in SUTs were highly conserved among the close orthologs; in contrast, there were variations among the paralogous SUTs in Sacchuarm. Though with the high polyploidy level, gene allelic haplotype comparative analysis showed that the examined four SsSUT members exhibited conservations of gene structures and amino acid sequences among the allelic haplotypes accompanied by variations of intron sizes. Gene expression analyses were performed for tissues from seedlings under drought stress and mature plants of three Saccharum species (S.officinarnum, S.spotaneum and S.robustum). Both SUT1 and SUT4 expressed abundantly at different conditions. SUT2 had similar expression level in all of the examined tissues, but SUT3 was undetectable. Both of SUT5 and SUT6 had lower expression level than other gene member, and expressed stronger in source leaves and are likely to play roles in phloem loading. In the seeding plant leave under water stress, four genes SUT1, SUT2, SUT4 and SUT5 were detectable. In these detectable genes, SUT1 and SUT4 were down regulated, while, SUT2 and SUT5 were up regulated.ConclusionsIn this study, we presented the first comprehensive genomic study for a whole gene family, the SUT family, in Saccharum. We speculated that there were six SUT members in the S. spotaneum genome. Out of the six members, SsSUTs, SsSUT5 and SsSUT6 were recent duplication genes accompanied by rapid evolution, while, SsSUT2 and SsSUT4 were the ancient members in the families. Despite the high polypoidy genome, functional redundancy may not exist among the SUTs allelic haplotypes supported by the evidence of strong purifying selection of the gene allele. SUT3 could be a low active member in the family because it is undetectable in our study, but it might not be a pseudogene because it harbored integrated gene structure. SUT1 and SUT4 were the main members for the sucrose transporter, while, these SUTs had sub-functional divergence in response to sucrose accumulation and plant development in Saccharum.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2419-6) contains supplementary material, which is available to authorized users.