Sucrose Phosphate Synthase Genes in Plants: Its Role and Practice for Crop Improvement.

Plants convert solar energy and carbon dioxide into organic compounds through photosynthesis. Sucrose is the primary carbonate produced during photosynthesis. Sucrose phosphate synthase (SPS) is the key enzyme controlling sucrose biosynthesis in plants. There are at least three SPS gene families in higher plants, named A, B, and C. However, in monocotyledonous plants from Poaceae, there are at least five SPS gene families, named A, B, C, DIII, and DIV. Each family of SPS genes in different plants shows a divergent expression pattern. So different families of SPS genes participate in diverse biological functions, including sucrose accumulation, plant growth and production, and abiotic stress tolerance. SPS activity in plants is regulated by exogenous factors through gene expression and reversible protein phosphorylation. It is a practicable way to improve crop traits through SPS gene transformation. This work analyzes the cloning, phylogeny, and regulatory mechanism of the SPS gene in plants, reviews its biological function as well as its role in crop improvement, and discusses the challenges and future perspectives. This paper can serve as a reference for further study on plant SPS genes and eventually for crop improvement.

Transcriptomic and Proteomic Landscape of Sugarcane Response to Biotic and Abiotic Stressors.

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.

Integrated Transcriptome and Metabolome Analysis to Identify Sugarcane Gene Defense against Fall Armyworm (Spodoptera frugiperda) Herbivory.

Sugarcane is the most important sugar crop, contributing ≥80% to total sugar production around the world. Spodoptera frugiperda is one of the main pests of sugarcane, potentially causing severe yield and sugar loss. The identification of key defense factors against S. frugiperda herbivory can provide targets for improving sugarcane resistance to insect pests by molecular breeding. In this work, we used one of the main sugarcane pests, S. frugiperda, as the tested insect to attack sugarcane. Integrated transcriptome and metabolomic analyses were performed to explore the changes in gene expression and metabolic processes that occurred in sugarcane leaf after continuous herbivory by S. frugiperda larvae for 72 h. The transcriptome analysis demonstrated that sugarcane pest herbivory enhanced several herbivory-induced responses, including carbohydrate metabolism, secondary metabolites and amino acid metabolism, plant hormone signaling transduction, pathogen responses, and transcription factors. Further metabolome analysis verified the inducement of specific metabolites of amino acids and secondary metabolites by insect herbivory. Finally, association analysis of the transcriptome and metabolome by the Pearson correlation coefficient method brought into focus the target defense genes against insect herbivory in sugarcane. These genes include amidase and lipoxygenase in amino acid metabolism, peroxidase in phenylpropanoid biosynthesis, and pathogenesis-related protein 1 in plant hormone signal transduction. A putative regulatory model was proposed to illustrate the sugarcane defense mechanism against insect attack. This work will accelerate the dissection of the mechanism underlying insect herbivory in sugarcane and provide targets for improving sugarcane variety resistance to insect herbivory by molecular breeding.

Proteomics data analysis using multiple statistical approaches identified proteins and metabolic networks associated with sucrose accumulation in sugarcane.

BACKGROUND: Sugarcane is the most important sugar crop, contributing > 80% of global sugar production. High sucrose content is a key target of sugarcane breeding, yet sucrose improvement in sugarcane remains extremely slow for decades. Molecular breeding has the potential to break through the genetic bottleneck of sucrose improvement. Dissecting the molecular mechanism(s) and identifying the key genetic elements controlling sucrose accumulation will accelerate sucrose improvement by molecular breeding. In our previous work, a proteomics dataset based on 12 independent samples from high- and low-sugar genotypes treated with ethephon or water was established. However, in that study, employing conventional analysis, only 25 proteins involved in sugar metabolism were identified . RESULTS: In this work, the proteomics dataset used in our previous study was reanalyzed by three different statistical approaches, which include a logistic marginal regression, a penalized multiple logistic regression named Elastic net, as well as a Bayesian multiple logistic regression method named Stochastic search variable selection (SSVS) to identify more sugar metabolism-associated proteins. A total of 507 differentially abundant proteins (DAPs) were identified from this dataset, with 5 of them were validated by western blot. Among the DAPs, 49 proteins were found to participate in sugar metabolism-related processes including photosynthesis, carbon fixation as well as carbon, amino sugar, nucleotide sugar, starch and sucrose metabolism. Based on our studies, a putative network of key proteins regulating sucrose accumulation in sugarcane is proposed, with glucose-6-phosphate isomerase, 2-phospho-D-glycerate hydrolyase, malate dehydrogenase and phospho-glycerate kinase, as hub proteins. CONCLUSIONS: The sugar metabolism-related proteins identified in this work are potential candidates for sucrose improvement by molecular breeding. Further, this work provides an alternative solution for omics data processing.

Transcriptome Profiling Reveals Genes Related to Sex Determination and Differentiation in Sugarcane Borer (Chilo sacchariphagus Bojer).

Chilo sacchariphagus Bojer is an important sugarcane pest globally. Along with genetic modification strategies, the sterile insect technique (SIT) has gained more attention as an environment-friendly method for pest control. The identification of key genes associated with sex determination and differentiation will provide important basic information for this control strategy. As such, the transcriptome sequencing of female and male adults was conducted in order to understand the sex-biased gene expression and molecular basis of sex determination and differentiation in this species. A total of 60,429 unigenes were obtained; among them, 34,847 genes were annotated. Furthermore, 11,121 deferentially expressed genes (DEGs) were identified, of which 8986 were male-biased and 2135 were female-biased genes. The male-biased genes were enriched for carbon metabolism, peptidase activity and transmembrane transport, while the female-biased genes were enriched for the cell cycle, DNA replication, and the MAPK signaling pathway. In addition, 102 genes related to sex-determination and differentiation were identified, including the protein toll, ejaculatory bulb-specific protein, fruitless, transformer-2, sex-lethal, beta-Catenin, sox, gata4, beta-tubulin, cytosol aminopeptidase, seminal fluid, and wnt4. Furthermore, transcription factors such as myb, bhlh and homeobox were also found to be potentially related to sex determination and differentiation in this species. Our data provide new insights into the genetic elements associated with sex determination and differentiation in Chilo sacchariphagus, and identified potential candidate genes to develop pest-control strategies.