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Sugarcane is a significant primitive source of sugar and energy worldwide. The progress in enhancing the sugar content in sugarcane cultivars remains limited due to an insufficient understanding of specific genes related to sucrose production. The present investigation examined the enzyme activities, levels of reducing and non-reducing sugars, and transcript expression using RT-qPCR to assess the gene expression associated with sucrose metabolism in a high-sucrose sugarcane clone (GXB9) in comparison to a low-sucrose sister clone (B9). Sucrose phosphate synthase (SPS), sucrose phosphate phosphatase (SPP), sucrose synthase (SuSy), cell wall invertase (CWI), soluble acid invertase (SAI), and neutral invertase (NI) are essential enzymes involved in sucrose metabolism in sugarcane. The activities of these enzymes were comparatively quantified and analyzed in immature and maturing internodes of the high- and low-sucrose clones. The results showed that the higher-sucrose-accumulating clone had greater sucrose concentrations than the low-sucrose-accumulating clone; however, maturing internodes had higher sucrose levels than immature internodes in both clones. Hexose concentrations were higher in immature internodes than in maturing internodes for both clones. The SPS and SPP enzymes activities were higher in the high-sucrose-storing clone than in the low-sucrose clone. SuSy activity was higher in the low-sucrose clone than in the high-sucrose clone; further, the degree of SuSy activity was higher in immature internodes than in maturing internodes for both clones. The SPS gene expression was considerably higher in mature internodes of the high-sucrose clones than the low-sucrose clone. Conversely, the SuSy gene exhibited up-regulated expression in the low-sucrose clone. The enhanced expression of SPS in the high-sucrose clone compared to the low-sucrose clone suggests that SPS plays a major role in the increased accumulation of sucrose. These findings provide the opportunity to improve sugarcane cultivars by regulating the activity of genes related to sucrose metabolism using transgenic techniques. [ABSTRACT FROM AUTHOR]

Sugarcane (Saccharum spp. hybrid) is the chief source of sugar and biofuel globally and is prominent among cash crops. Sucrose is the main required product in sugarcane, and many studies have been performed to understand the phenomena of sucrose synthesis, metabolism, and accumulation in sugarcane. However, none of the studies concluded that a single gene is responsible for the sucrose content. Instead, a complex mechanism consisting of several genes, such as sucrose phosphate synthase genes (SPS1, SPS2, SPS4, SPS5), sucrose synthase genes (SuSy1, SuSy2, SuSy4), invertase genes (INV, CWIN, NIN1, CINV2), and phytohormone, trehalose, transcription factor (TF), protein kinase, and sugar transporter genes are working spatiotemporally in sugarcane. Currently, omics approaches like transcriptomics, proteomics, and metabolomics are also being used to explore the sugar metabolism in sugarcane, but integrated transcriptomic, proteomic, and metabolomic studies have been less reported. The results obtained from the integrated analysis of transcriptomics, proteomics, and metabolomics are more reliable because the strong gene expression, received in the form of abundant mRNA, does not guarantee the plentiful existence of associated proteins or their particular activity in the target cells or tissues, which discloses the restraint of single interpretation and stresses the significance of the integrated analysis of transcriptomics, proteomics, and metabolomics. This review highlights different genes and molecules contributing to sugar metabolism at different stages and the significance of omics approaches in explaining sucrose metabolism, especially sucrose accumulation in sugarcane. It is also a vital source of knowledge for sugarcane breeders, particularly associated with sucrose content improvement and bioethanol energy production. [ABSTRACT FROM AUTHOR]

Sugarcane, a C4 plant, provides most of the world's sugar, and a substantial amount of renewable bioenergy, due to its unique sugar-accumulating and feedstock properties. Brazil, India, China, and Thailand are the four largest sugarcane producers worldwide, and the crop has the potential to be grown in arid and semi-arid regions if its stress tolerance can be improved. Modern sugarcane cultivars which exhibit a greater extent of polyploidy and agronomically important traits, such as high sugar concentration, biomass production, and stress tolerance, are regulated by complex mechanisms. Molecular techniques have revolutionized our understanding of the interactions between genes, proteins, and metabolites, and have aided in the identification of the key regulators of diverse traits. This review discusses various molecular techniques for dissecting the mechanisms underlying the sugarcane response to biotic and abiotic stresses. The comprehensive characterization of sugarcane's response to various stresses will provide targets and resources for sugarcane crop improvement. [ABSTRACT FROM AUTHOR]

For quadrotor control applications, it is necessary to rely on attitude angle changes to indirectly achieve the position trajectory tracking purpose. Several existing literature studies omit the non-negligible attitude transients in the position controller design for this kind of cascade system. The result leads to the position tracking performance not being as good as expected. In fact, the transient behavior of the attitude tracking response cannot be ignored. Therefore, the closed-loop stability of the attitude loop as well as the position tracking should be considered simultaneously. In this study, the flight controller design of the position and attitude control loops is presented based on an integral backstepping control algorithm. This control algorithm relies on the derivatives of the associated virtual control laws for implementation. Examining existing literature, the derivatives of the virtual control law are realized approximated by numerical differentiations. Nevertheless, in practical scenarios, the numerical differentiations will cause the chattering phenomenon of control signals in the presence of unavoidable measurement noise. The noise-induced control signals may further cause damage to the actuators or even diverge the system response. To address this issue, the analytic form for the derivative of the virtual control law is derived. The time derivative virtual control law is analyzed and split into the disturbance-independent compensable and disturbance-dependent non-compensable terms. By utilizing the compensable term, the control chattering due to the differentiation of the noise can be avoided significantly. The simulation results reveal that the proposed control algorithm has a better position tracking performance than the traditional dual-loop control scheme. Meanwhile, a relatively smooth control signal can be obtained for a realistic control algorithm realization. Simulations are provided to illustrate the position tracking issue of a quadrotor and to demonstrate the effectiveness of the proposed compromised control scheme. [ABSTRACT FROM AUTHOR]

Sugarcane, a cash crop, is easily affected by low temperature, which results in a decrease in yield and sugar production. Breeding a new variety with cold tolerance is an essential strategy to reduce loss from cold stress. The identification of germplasms and genes/proteins with cold tolerance is a vital step in breeding sugarcane varieties with cold tolerance via a conventional program and molecular technology. In this study, the physiological and biochemical indices of 22 genotypes of S. spontaneum were measured, and the membership function analysis method was used to comprehensively evaluate the cold tolerance ability of these genotypes. The physiological and biochemical indices of these S. spontaneum genotypes showed a sophisticated response to low temperature. On the basis of the physiological and chemical indices, the genotypes were classified into different cold tolerance groups. Then, the high-tolerance genotype 1027 and the low-tolerance genotype 3217 were selected for DIA-based proteomic analysis by subjecting them to low temperature. From the four comparison groups, 1123, 1341, 751, and 1693 differentially abundant proteins (DAPs) were identified, respectively. The DAPs based on genotypes or treatments participated in distinct metabolic pathways. Through detailed analysis of the DAPs, some proteins related to protein homeostasis, carbohydrate and energy metabolism, amino acid transport and metabolism, signal transduction, and the cytoskeleton may be involved in sugarcane tolerance to cold stress. Furthermore, five important proteins related to cold tolerance were discovered for the first time in this study. This work not only provides the germplasms and candidate target proteins for breeding sugarcane varieties with cold tolerance via a conventional program and molecular breeding, but also helps to accelerate the determination of the molecular mechanism underlying cold tolerance in sugarcane. [ABSTRACT FROM AUTHOR]

Pathogen infection seriously affects plant development and crop productivity, sometimes causing total crop failure. In this study, artificial stab inoculation was used to inoculate sugarcane smut. The changes in leaf gas exchange, chlorophyll fluorescence variables, and related defense enzyme activities were measured in sugarcane cultivar ROC22 after pathogen infection. The results showed that the net photosynthetic rate (Pn), stomatal conductance (gs), and transpiration rate (Tr) downregulated in the first three days after smut infection and upregulated on the fourth day; intercellular CO2 concentration (Ci) increased in the first three days of smut infection and reduced on the fourth day. The chlorophyll fluorescence parameters, i.e., Fo, Fm, Fv/Fm, Fs, and Fv′/Fm′ decreased at the initial stage of pathogen infection but increased rapidly up to 3 days after smut infection. It can be seen that sugarcane seedlings showed a positive response to pathogen infection. The correlation coefficient relationship between Pn, gs, and Tr reached above 0.800, showing a significant correlation; Ci was positively correlated with Fv′/Fm′ and ΦPSII, reaching above 0.800 and showing a significant correlation; Fo positively correlated with Fv/Fm, Fs, and ETR; Fv /Fm was positively correlated with Fv′/Fm′; Fs significantly correlated with Fv′/Fm′; and Fv′/Fm′ positively correlated with ΦPSII. After inoculation with smut, the related defense enzymes, i.e., POD, SOD, PPO, and PAL, were increased and upregulated; photosynthetic parameters can be associated with an increase in enzymatic activities. The results of this study will help to further study of the response mechanism to smut in the sugarcane growing period and provide a theoretical reference for sugarcane resistance to smut breeding. [ABSTRACT FROM AUTHOR]

Sugarcane (Saccharum officinarum L.) is one of the world's highly significant commercial crops. The amounts of synthetic nitrogen (N2) fertilizer required to grow the sugarcane plant at its initial growth stages are higher, which increases the production costs and adverse environmental consequences globally. To combat this issue, sustainable environmental and economic concerns among researchers are necessary. The endophytic diazotrophs can offer significant amounts of nitrogen to crops through the biological nitrogen fixation mediated nif gene. The nifH gene is the most extensively utilized molecular marker in nature for studying N2 fixing microbiomes. The present research intended to determine the existence of novel endophytic diazotrophs through culturable and unculturable bacterial communities (EDBCs). The EDBCs of different tissues (root, stem, and leaf) of five sugarcane cultivars (Saccharum officinarum L. cv. Badila, S. barberi Jesw.cv Pansahi, S. robustum, S. spontaneum, and S. sinense Roxb.cv Uba) were isolated and molecularly characterized to evaluate N2 fixation ability. The diversity of EDBCs was observed based on nifH gene Illumina MiSeq sequencing and a culturable approach. In this study, 319766 operational taxonomic units (OTUs) were identified from 15 samples. The minimum number of OTUs was recorded in leaf tissues of S. robustum and maximum reads in root tissues of S. spontaneum. These data were assessed to ascertain the structure, diversity, abundance, and relationship between the microbial community. A total of 40 bacterial families with 58 genera were detected in different sugarcane species. Bacterial communities exhibited substantially different alpha and beta diversity. In total, 16 out of 20 genera showed potent N2-fixation in sugarcane and other crops. According to principal component analysis (PCA) and hierarchical clustering (Bray–Curtis dis) evaluation of OTUs, bacterial microbiomes associated with root tissues differed significantly from stem and leaf tissues of sugarcane. Significant differences often were observed in EDBCs among the sugarcane tissues. We tracked and validated the plethora of individual phylum strains and assessed their nitrogenase activity with a culture-dependent technique. The current work illustrated the significant and novel results of many uncharted endophytic microbial communities in different tissues of sugarcane species, which provides an experimental system to evaluate the biological nitrogen fixation (BNF) mechanism in sugarcane. The novel endophytic microbial communities with N2-fixation ability play a remarkable and promising role in sustainable agriculture production. [ABSTRACT FROM AUTHOR]

Sugarcan e is a major crop for sugar and biofuel production and is cultivated in tropical and subtropical areas worldwide. Sugarcane growth is constrained because of winter's low-temperature stress, and cold resistance is an important limitation in sugarcane growth enhancement. Therefore, in this study, we identified a gene involved in the low-temperature stress response of sugarcane. Calcineurin B-like (CBL) protein is a calcium signal receptor involved in the cold stress response. Five sugarcane CBL genes were cloned, sequenced, and named SoCBL1, SoCBL3, SoCBL5, SoCBL6, and SoCBL9. The protein sequences of these genes were analyzed. The calculated molecular weight of these proteins was 24.5, 25.9, 25.2, 25.6, and 26.3 kD, respectively. Subcellular localization analysis revealed that SoCBL1, SoCBL3, SoCBL6, and SoCBL9 were situated in the cytoplasm, while SoCBL5 was present in mitochondria. Secondary structure analysis showed that these five CBL proteins had similar secondary structures. Conserved domain analysis displayed that each sugarcane CBL protein contained three conserved EF domains. According to the self-expanding values of the phylogenetic tree, the CBL gene family was divided into four groups. The CBL1 and CBL9 genes were classified into one group, illustrating that these two genes might possess a similar function. The expression analysis of the SoCBL gene under low temperatures showed that SoCBL3 and SoCBL5 were affected significantly, while SoCBL1 and SoCBL9 were less affected. These results demonstrate that the CBL genes in sugarcane have similar characteristics and present differences in genetic diversity and gene expression response to low temperatures. Therefore, these genes might be novel candidates for fighting cold stress in sugarcane. [ABSTRACT FROM AUTHOR]

Nano-fertilizers (NFs) significantly improve soil quality and plant growth performance and enhance crop production with quality fruits/grains. The management of macro-micronutrients is a big task globally, as it relies predominantly on synthetic chemical fertilizers which may not be environmentally friendly for human beings and may be expensive for farmers. NFs may enhance nutrient uptake and plant production by regulating the availability of fertilizers in the rhizosphere; extend stress resistance by improving nutritional capacity; and increase plant defense mechanisms. They may also substitute for synthetic fertilizers for sustainable agriculture, being found more suitable for stimulation of plant development. They are associated with mitigating environmental stresses and enhancing tolerance abilities under adverse atmospheric eco-variables. Recent trends in NFs explored relevant agri-technology to fill the gaps and assure long-term beneficial agriculture strategies to safeguard food security globally. Accordingly, nanoparticles are emerging as a cutting-edge agri-technology for agri-improvement in the near future. Interestingly, they do confer stress resistance capabilities to crop plants. The effective and appropriate mechanisms are revealed in this article to update researchers widely. [ABSTRACT FROM AUTHOR]

Soil salinity causes severe environmental stress that affects agriculture production and food security throughout the world. Salt-tolerant plant-growth-promoting rhizobacteria (PGPR) and nitric oxide (NO), a distinctive signaling molecule, can synergistically assist in the alleviation of abiotic stresses and plant growth promotion, but the mechanism by which this happens is still not well known. In the present study, in a potential salt-tolerant rhizobacteria strain, ASN-1, growth up to 15% NaCl concentration was achieved with sugarcane rhizosphere soil. Based on 16S-rRNA gene sequencing analysis, the strain ASN-1 was identified as a Bacillus xiamenensis. Strain ASN-1 exhibits multiple plant-growth-promoting attributes, such as the production of indole-3-acetic acid, 1-aminocyclopropane-1-carboxylate deaminase, siderophores, HCN, ammonia, and exopolysaccharides as well as solubilized phosphate solubilization. Biofilm formation showed that NO enhanced the biofilm and root colonization capacity of the PGPR strain ASN-1 with host plants, evidenced by scanning electron microscopy. The greenhouse study showed that, among the different treatments, the combined application of PGPR and sodium nitroprusside (SNP) as an NO donor significantly (p ≤ 0.05) enhanced sugarcane plant growth by maintaining the relative water content, electrolyte leakage, gas exchange parameters, osmolytes, and Na+/K+ ratio. Furthermore, PGPR and SNP fertilization reduced the salinity-induced oxidative stress in plants by modulating the antioxidant enzyme activities and stress-related gene expression. Thus, it is believed that the acquisition of advanced information about the synergistic effect of salt-tolerant PGPR and NO fertilization will reduce the use of harmful chemicals and aid in eco-friendly sustainable agricultural production under salt stress conditions. [ABSTRACT FROM AUTHOR]

Silicon (Si) has never been acknowledged as a vital nutrient though it confers a crucial role in a variety of plants. Si may usually be expressed more clearly in Si-accumulating plants subjected to biotic stress. It safeguards several plant species from disease. It is considered as a common element in the lithosphere of up to 30% of soils, with most minerals and rocks containing silicon, and is classified as a "significant non-essential" element for plants. Plant roots absorb Si, which is subsequently transferred to the aboveground parts through transpiration stream. The soluble Si in cytosol activates metabolic processes that create jasmonic acid and herbivore-induced organic compounds in plants to extend their defense against biotic stressors. The soluble Si in the plant tissues also attracts natural predators and parasitoids during pest infestation to boost biological control, and it acts as a natural insect repellent. However, so far scientists, policymakers, and farmers have paid little attention to its usage as a pesticide. The recent developments in the era of genomics and metabolomics have opened a new window of knowledge in designing molecular strategies integrated with the role of Si in stress mitigation in plants. Accordingly, the present review summarizes the current status of Si-mediated plant defense against insect, fungal, and bacterial attacks. It was noted that the Si-application quenches biotic stress on a long-term basis, which could be beneficial for ecologically integrated strategy instead of using pesticides in the near future for crop improvement and to enhance productivity. [ABSTRACT FROM AUTHOR]

Abiotic stresses are the major constraints in agricultural crop production across the globe. The use of some plant–microbe interactions are established as an environment friendly way of enhancing crop productivity, and improving plant development and tolerance to abiotic stresses by direct or indirect mechanisms. Silicon (Si) can also stimulate plant growth and mitigate environmental stresses, and it is not detrimental to plants and is devoid of environmental contamination even if applied in excess quantity. In the present review, we elaborate the interactive application of Si and plant growth promoting rhizobacteria (PGPRs) as an ecologically sound practice to increase the plant growth rate in unfavorable situations, in the presence of abiotic stresses. Experiments investigating the combined use of Si and PGPRs on plants to cope with abiotic stresses can be helpful in the future for agricultural sustainability. [ABSTRACT FROM AUTHOR]

Silicon (Si) is not categorized as a biologically essential element for plants, yet a great number of scientific reports have shown its significant effects in various crop plants and environmental variables. Plant Si plays biologically active role in plant life cycle, and the significant impact depends on its bioaccumulation in plant tissues or parts. In particular, it has been investigated for its involvement in limited irrigation management. Therefore, this experiment was conducted to examine the effect of Si application in eco-physiological, enzymatic and non-enzymatic activities of sugarcane plants against water stress. Four irrigation levels, i.e., normal (100–95% of soil moisture), 80–75, 55–50, and 35–30% of soil moisture were treated for the sugarcane cultivar GT 42 plants supplied with 0, 100, 200, 300, 400 and 500 mg Si L−1 and exposed for 60 days after Si application. Under stress, reduction in plant length (~26–67%), leaf area-expansion (~7–51%), relative water content (~18–57%), leaf greenness (~12–35%), photosynthetic pigments (~12–67%), physiological responses such as photosynthesis (22–63%), stomatal conductance (~25–61%), and transpiration rate (~32–63%), and biomass production were observed in the plants without Si application. The drought condition also inhibited the activities of antioxidant enzymes like catalase (~10–52%), peroxidase (ca. 4–35), superoxide dismutase (10–44%) and enhanced proline (~73–410%), and malondialdehyde content (ca. 15–158%), respectively. However, addition of Si ameliorated drought induced damage in sugarcane plants. The findings suggest that the active involvement of Si in sugarcane responsive to water stress ranges from plant performance and physiological processes, to antioxidant defense systems. [ABSTRACT FROM AUTHOR]

Nitrogen (N) plays an important role in sugarcane (Saccharum spp. hybrids) growth and development; however, long-term effects of N application levels on cane and sugar production in different sugarcane cultivars under field conditions remain unclear. In this study, we investigate the agronomic, yield, and quality traits in three sugarcane cultivars (GT11, B9, and ROC22) under different N levels (0, 150, and 300 kg/ha urea) from 2015 to 2019. Continuous four-year field experiments of plant and ratoon crops were carried out by using two-factor split-plot design. The results showed that N fertilizer application improved the tillering rate, stalk diameter, plant height, stalk weight, millable stalks/ha, cane yield, sugar yield and juice rate of cane, and the difference between N application and non-N application was significant. The cane yield, millable stalks/ha, juice rate, and juice gravity purity increased with the increase of N application, but the milled juice brix and sucrose % cane decreased with the increase of N application. The sugar yield was the highest at 150 kg/ha urea application, while the cane yield was the highest at 300 kg/ha urea application. Different N fertilizer application levels significantly regulated the activities of glutamic pyruvic transaminase (GPT) and glutamic oxaloacetic transaminase (GOT) and the contents of chlorophyll and nitrate N in plant leaves, which reflected the regulation in nitrogen metabolism and alteration in dry matter production and distribution, cane yield and sugar accumulation in different sugarcane cultivars. During the four-year experiment duration, the cane yield and sugar yield generally showed ROC22 > B9 > GT11. These data suggested that 300 kg/ha urea application was suitable for the plant and first ratoon crops, and 150 kg/ha urea application was suitable for the second and third ratoon crops. Both cane and sugar yields could be the highest in a four-year production cycle under this circumstance. [ABSTRACT FROM AUTHOR]

Smut disease is caused by Sporisorium scitamineum, an important sugarcane fungal pathogen causing an extensive loss in yield and sugar quality. The available literature suggests that there are two types of smut resistance mechanisms: external resistance by physical or chemical barriers and intrinsic internal resistance mechanisms operating at host–pathogen interaction at cellular and molecular levels. The nature of smut resistance mechanisms, however, remains largely unknown. The present study investigated the changes in proteome occurring in two sugarcane varieties with contrasting susceptibility to smut—F134 and NCo310—at whip development stage after S. scitamineum infection. Total proteins from pathogen inoculated and uninoculated (control) leaves were separated by two-dimensional gel electrophoresis (2D-PAGE). Protein identification was performed using BLASTp and tBLASTn against NCBI nonredundant protein databases and EST databases, respectively. A total of thirty proteins spots representing differentially expressed proteins (DEPs), 16 from F134 and 14 from NCo310, were identified and analyzed by MALDI-TOF/TOF MS. In F134, 4 DEPs were upregulated and nine were downregulated, while, nine were upregulated and three were downregulated in NCo310. The DEPs were associated with DNA binding, metabolic processes, defense, stress response, photorespiration, protein refolding, chloroplast, nucleus and plasma membrane. Finally, the expression of CAT, SOD, and PAL with recognized roles in S. scitamineum infection in both sugarcane verities were analyzed by real-time quantitative PCR (RT-qPCR) technique. Identification of genes critical for smut resistance in sugarcane will increase our knowledge of S. scitamineum-sugarcane interaction and help to develop molecular and conventional breeding strategies for variety improvement. [ABSTRACT FROM AUTHOR]