Genome-wide identification and expression profiling analysis of sucrose synthase (SUS) and sucrose phosphate synthase (SPS) genes family in Actinidia chinensis and A. eriantha

Bioinformatics and Functional Analysis of OsASMT1 Gene in Response to Abiotic Stress

The study aimed to elucidate the functional characteristics of OsASMT1 gene under copper (Cu) or sodium chloride (NaCl) stress. Bioinformatics scrutiny unveiled that OsASMT1 is situated on chromosome 9. Its protein architecture, comprising dimerization and methyltransferase domains, showed significant similarities to OsASMT2 and OsASMT3. High expression in roots and panicles, along with abiotic stress putative cis-regulatory elements in the promoter, indicated potential stress responsiveness. Real-time quantitative PCR confirmed OsASMT1 induction under Cu and NaCl stress in rice. Surprisingly, yeast expressing OsASMT1 did not exhibit enhanced resistance to abiotic stresses. The results of subcellular localization analysis indicated that OsASMT1 plays a role in the cytoplasm. While OsASMT1 responded to Cu and NaCl stress in rice, its heterologous expression in yeast failed to confer abiotic stress resistance, highlighting the need for further investigation of its functional implications.

Current perspectives on the regulatory mechanisms of sucrose accumulation in sugarcane

Sugars transported from leaves (source) to stems (sink) energize cell growth, elongation, and maintenance. which are regulated by a variety of genes. This review reflects progress and prospects in the regulatory mechanism for maximum sucrose accumulation, including the role of sucrose metabolizing enzymes, sugar transporters and the elucidation of post-transcriptional control of sucrose-induced regulation of translation (SIRT) in the accumulation of sucrose. The current review suggests that SIRT is emerging as a significant mechanism controlling Scbzip44 activities in response to endogenous sugar signals (via the negative feedback mechanism). Sucrose-controlled upstream open reading frame (SC-uORF) exists at the 5' leader region of Scbzip44's main ORF, which inhibits sucrose accumulation through post-transcriptional regulatory mechanisms. Sucrose transporters (SWEET1a/4a/4b/13c, TST, SUT1, SUT4 and SUT5) are crucial for sucrose translocation from source to sink. Particularly, SWEET13c was found to be a major contributor to the efflux in the transportation of stems. Tonoplast sugar transporters (TSTs), which import sucrose into the vacuole, suggest their tissue-specific role from source to sink. Sucrose cleavage has generally been linked with invertase isozymes, whereas sucrose synthase (SuSy)-catalyzed metabolism has been associated with biosynthetic processes such as UDP-Glc, cellulose, hemicellulose and other polymers. However, other two key sucrose-metabolizing enzymes, such as sucrose-6-phosphate phosphohydrolase (S6PP) and sucrose phosphate synthase (SPS) isoforms, have been linked with sucrose biosynthesis. These findings suggest that manipulation of genes, such as overexpression of SPS genes and sucrose transporter genes, silencing of the SC-uORF of Scbzip44 (removing the 5' leader region of the main ORF that is called SIRT-Insensitive) and downregulation of the invertase genes, may lead to maximum sucrose accumulation. This review provides an overview of sugarcane sucrose-regulating systems and baseline information for the development of cultivars with higher sucrose accumulation.

Research overview on the genetic mechanism underlying the biosynthesis of polysaccharide in tuber plants

Tuber plants are of great significance in the world as human food crops. Polysaccharides, important metabolites in tuber plants, also serve as a source of innovative drugs with significant pharmacological effects. These drugs are particularly known for their immunomodulation and antitumor properties. To fully exploit the potential value of tuber plant polysaccharides and establish a synthetic system for their targeted synthesis, it is crucial to dissect their metabolic processes and genetic regulatory mechanisms. In this article, we provide a comprehensive summary of the basic pathways involved in the synthesis of various types of tuber plant polysaccharides. We also outline the key research progress that has been made in this area in recent years. We classify the main types and functions of tuber plant polysaccharides and analyze the biosynthetic processes and genetic regulation mechanisms of key enzymes involved in the metabolic pathways of starch, cellulose, pectin, and fructan in tuber plants. We have identified hexokinase and glycosyltransferase as the key enzymes involved in the polysaccharide synthesis process. By elucidating the synthesis pathway of polysaccharides in tuber plants and understanding the underlying mechanism of action of key enzymes in the metabolic pathway, we can provide a theoretical framework for enhancing the yield of polysaccharides and other metabolites in plant culture cells. This will ultimately lead to increased production efficiency.

Metabolomics combined with physiology and transcriptomics reveal key metabolic pathway responses in apple plants exposure to different selenium concentrations

Selenium (Se) can be absorbed by plants, thereby affects plant physiological activity, interferes gene expression, alters metabolite content and influences plant growth. However, the molecular mechanism underlying the plant response to Se remains unclear. In this study, apple plants were exposed to Se at concentrations of 0, 3, 6, 9, 12, 24, and 48 μM. Low concentrations of Se promoted plant growth, while high Se concentrations (≥24 μM) reduced photosynthesis, disturbed carbon and nitrogen metabolism, damaged the antioxidant system, and ultimately inhibited plant growth. The transcriptome and metabolome revealed that Se mainly affected three pathways, namely the 'biosynthesis of amino acids', 'starch and sucrose metabolism', and 'phenylpropanoid biosynthesis' pathways. 9 μM Se improved the synthesis, catabolism and utilization of amino acids and sugars, ultimately promoted plant growth. However, 24 μM Se up-regulated the related genes expression of PK, GPT, P5CS, SUS, SPS and CYP98A, and accumulated a large number of osmoregulation substances, such as citric acid, L-proline, D-sucrose and chlorogenic acid in the roots, ultimately affected the balance between plant growth and defense. In conclusion, this study reveals new insights into the key metabolic pathway in apple plants responses to Se.

ZjHXK5 and ZjHXK6 negatively regulate the sugar metabolism of Ziziphus jujuba Mill

Hexokinase (HXK) plays a crucial role in plants, catalyzing the phosphorylation of hexose substances, which is one of the key steps in sugar metabolism and energy production. While HXK genes have been well-studied in model plants, the evolutionary and functional characteristics of HXK gene family in jujube is unknow. In this study, the HXK gene family members were identified by bioinformatics methods, the key members regulating glucose metabolism were identified by transcriptome data, and finally the function of the key genes was verified by instantaneous and stable genetic transformation. Our results showed that seven HXK genes were identified in the jujube genome, all of which were predict located in the chloroplast and contain Hexokinase-1 (PF00349) and Hexokinase-2 (PF03727) conserved domains. Most of HXK proteins were transmembrane protein with stable, lipid-soluble, hydrophilic. The secondary structure of ZjHXK proteins main α-helix, and contains two distinct tertiary structure. All ZjHXK genes contain nine exons and eight introns. Predictions of cis-regulatory elements indicate that the promoter region of ZjHXK contains a large number of MeJA responsive elements. Finally, combined with the analysis of the relationship between the expression and glucose metabolism, found that ZjHXK5 and ZjHXK6 may the key genes regulating sugar metabolism. Transient overexpression of ZjHXK5 and ZjHXK6 on jujube, or allogeneic overexpression of ZjHXK5 and ZjHXK6 on tomato would significantly reduce the content of total sugar and various sugar components. Transient silencing of ZjHXK5 and ZjHXK6 genes results in a significant increase in sucrose and total sugar content. Interestingly, the expression of ZjHXK5 and ZjHXK6 were also affected by methyl jasmonate.

MaNAC19-MaXB3 regulatory module mediates sucrose synthesis in banana fruit during ripening

Sucrose, a predominant sweetener in banana (Musa acuminata) fruit, determines sweetness and consumer preferences. Although sucrose phosphate synthase (SPS) is known to catalyze starch conversion into sucrose in banana fruit during the ripening process, the SPS regulatory mechanism during ripening still demands investigation. Hence, this study discovered that the MaSPS1 expression was promoted during ethylene-mediated ripening in banana fruit. MaNAC19, recognized as the MaSPS1 putative binding protein using yeast one-hybrid screening, directly binds to the MaSPS1 promoter, thereby transcriptionally activating its expression, which was verified by transient overexpression experiments, where the sucrose synthesis was accelerated through MaNAC19-induced transcription of MaSPS1. Interestingly, MaXB3, an ethylene-inhibited E3 ligase, was found to ubiquitinate MaNAC19, making it prone to proteasomal degradation, inhibiting transactivation of MaNAC19 to MaSPS1, thereby attenuating MaNAC19-promoted sucrose accumulation. This study's findings collectively illustrated the mechanistic basis of a MaXB3-MaNAC19-MaSPS1 regulatory module controlling sucrose synthesis during banana fruit ripening. These outcomes have broadened our understanding of the regulation mechanisms that contributed to sucrose metabolism occurring in transcriptional and post-transcriptional stages, which might help develop molecular approaches for controlling ripening and improving fruit quality.

Genome-Wide Identification and Evolution of the GRF Gene Family and Functional Characterization of PbGRF18 in Pear

Proteins encoded by the G-box regulating factor (GRF, also called 14-3-3) gene family are involved in protein-protein interactions and mediate signaling transduction, which play important roles in plant growth, development, and stress responses. However, there were no detailed investigations of the GRF gene family in pear at present. In this study, we identified 25 GRF family members in the pear genome. Based on a phylogenetic analysis, the 25 GRF genes were clustered into two groups; the ε group and the non-ε group. Analyses of the exon-intron structures and motifs showed that the gene structures were conserved within each of the ε and non-ε groups. Gene duplication analysis indicated that most of the PbGRF gene expansion that occurred in both groups was due to WGD/segmental duplication. Phosphorylation sites analysis showed that the main phosphorylation sites of PbGRF proteins were serine residues. For gene expression, five PbGRF genes (PbGRF7, PbGRF11, PbGRF16, PbGRF21, and PbGRF23) were highly expressed in fruits, and PbGRF18 was highly expressed in all tissues. Further analysis revealed that eight PbGRF genes were significantly differentially expressed after treatment with different sugars; the expression of PbGRF7, PbGRF8, and PbGRF11 significantly increased, implying the involvement of these genes in sugar signaling. In addition, subcellular localization studies showed that the tested GRF proteins localize to the plasma membrane, and transgenic analysis showed that PbGRF18 can increase the sugar content in tomato leaves and fruit. The results of our research establish a foundation for functional determination of PbGRF proteins, and will help to promote a further understanding of the regulatory network in pear fruit development.

Phosphorus and naphthalene acetic acid increased the seed yield by regulating carbon and nitrogen assimilation of flax

To evaluate the impact of phosphorus (P) combined with exogenous NAA on flax yield, enhance flax P utilization efficiency and productivity, minimize resource inputs and mitigate negative environmental and human effects. Therefore, it is crucial to comprehend the physiological and biochemical responses of flax to P and naphthylacetic acid (NAA) in order to guide future agronomic management strategies for increasing seed yield. A randomized complete block design trial was conducted under semi-arid conditions in Northwest China, using a factorial split-plot to investigate the effects of three P (0, 67.5, and 135.0 kg P2O5 ha-1) and three exogenous spray NAA levels (0, 20, and 40 mg NAA L-1) on sucrose phosphate synthase (SPS) and diphosphoribulose carboxylase (Rubisco) activities as well as nitrogen (N) and P accumulation and translocation in flax. Results indicated that the SPS and Rubisco activities, N and P accumulation at flowering and maturity along with assimilation and translocation post-flowering, fruiting branches per plant, tillers per plant, capsules per plant, and seed yield were 95, 105, 14, 27, 55, 15, 13, 110, 103, 82, 16, 61, 8, and 13% greater in the P treatments compared to those in the zero P treatment, respectively. Moreover, those characteristics were observed to be greater with exogenous spray NAA treatments compared to that no spray NAA treatment. Additionally, the maximum SPS and Rubisco activities, N and P accumulation, assimilation post-flowering and translocation, capsules per plant, and seed yield were achieved with the application of 67.5 kg P2O5 ha-1 with 20 mg NAA L-1. Therefore, these findings demonstrate that the appropriate combination of P fertilizer and spray NAA is an effective agronomic management strategy for regulating carbon and nitrogen assimilation by maintaining photosynthetic efficiency in plants to increase flax productivity.

Comprehensive metabolomics-based analysis of sugar composition and content in berries of 18 grape varieties

Xinjiang is the largest grape-producing region in China and the main grape cultivation area in the world. The Eurasian grape resources grown in Xinjiang are very rich in diversity. The sugar composition and content are the main factors that determine the quality of berries. However, there are currently no systematic reports on the types and contents of sugars in grapes grown in Xinjiang region. In this research, we evaluated the appearance and fruit maturity indicators of 18 grape varieties during fruit ripening and determined their sugar content using GC-MS. All cultivars primarily contained glucose, D-fructose, and sucrose. The glucose content in varieties varied from 42.13% to 46.80% of the total sugar, whereas the fructose and sucrose contents varied from 42.68% to 50.95% and 6.17% to 12.69%, respectively. The content of trace sugar identified in grape varieties varied from 0.6 to 2.3 mg/g. The comprehensive assessment by principal component analysis revealed strong positive correlations between some sugar components. A comprehensive study on the content and types of sugar will provide the foundation to determine the quality of grape cultivars and effective ways to utilize resources to improve sugar content through breeding.

Physiological and sucrose metabolic responses to waterlogging stress in balloon flower (Platycodon grandiflorus (Jacq.) A. DC)

Waterlogging stress is a major limiting factor resulting in stunted growth and loss of crop productivity, especially for root crops. However, physiological responses to waterlogging have been studied in only a few plant models. To gain insight into how balloon flower (Platycodon grandiflorus (Jacq.) A. DC) responds to waterlogging stress, we investigate changes to sucrose metabolism combined with a physiological analysis. Although waterlogging stress decreased the photosynthetic rate in balloon flower, leaves exhibited an increase in glucose (ninefold), fructose (4.7-fold), and sucrose (2.1-fold), indicating inhibition of sugar transport via the phloem. In addition, roots showed a typical response to hypoxia, such as the accumulation of proline (4.5-fold higher than in control roots) and soluble sugars (2.1-fold higher than in control roots). The activities and expression patterns of sucrose catabolizing enzymes suggest that waterlogging stress leads to a shift in the pathway of sucrose degradation from invertase to sucrose synthase (Susy), which consumes less ATP. Furthermore, we suggest that the waterlogging-stress-induced gene PlgSusy1 encodes the functional Susy enzyme, which may contribute to improving tolerance in balloon flower to waterlogging. As a first step toward understanding the waterlogging-induced regulatory mechanisms in balloon flower, we provide a solid foundation for further understanding waterlogging-induced alterations in source-sink relationships.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01310-y.

New Insights into MdSPS4-Mediated Sucrose Accumulation under Different Nitrogen Levels Revealed by Physiological and Transcriptomic Analysis

Nitrogen nutrition participates in many physiological processes and understanding the physiological and molecular mechanisms of apple responses to nitrogen is very significant for improving apple quality. This study excavated crucial genes that regulates sugar metabolism in response to nitrogen in apples through physiology and transcriptome analysis, so as to lay a theoretical foundation for improving fruit quality. In this paper, the content of sugar and organic acid in apple fruit at different developmental periods under different nitrogen levels (0, 150, 300, and 600 kg·hm^-2) were determined. Then, the transcriptomic analysis was performed in 120 days after bloom (DAB) and 150 DAB. The results showed that the fructose and glucose content were the highest at 120 DAB under 600 kg·hm^-2 nitrogen level. Meanwhile, different nitrogen treatments decreased malate content in 30 and 60 DAB. RNA-seq analysis revealed a total of 4537 UniGenes were identified as differentially expressed genes (DEGs) under nitrogen treatments. Among these DEGs, 2362 (52.06%) were up-regulated and 2175 (47.94%) were down-regulated. The gene co-expression clusters revealed that most DEGs were significantly annotated in the photosynthesis, glycolysis/gluconeogenesis, pyruvate metabolism, carbon metabolism, carbon fixation in photosynthetic organisms and plant hormone signal transduction pathways. The key transcription factor genes (ERF, NAC, WRKY, and C2H2 genes) were differentially expressed in apple fruit. Sugar and acid metabolism-related genes (e.g., HXK1, SPS4, SS2, PPC16-2, and MDH2 genes) exhibited significantly up-regulated expression at 120 DAB, whereas they were down-regulated at 150 DAB. Furthermore, the MdSPS4 gene overexpression positively promoted sucrose accumulation in apple callus and fruit. In conclusion, the combinational analysis of transcriptome and the functional validation of the MdSPS4 gene provides new insights into apple responses to different nitrogen levels.