Sucrose-starch Metabolism Research Articles

Analysis of Ethylene Signal Regulating Sucrose Metabolism in Strawberry Fruits Based on RNA-seq.

Ethylene is a key hormone that regulates the maturation and quality formation of horticultural crops, but its effects on non-respiratory climacteric fruits such as strawberries are not yet clear. In this study, strawberry fruits were treated with exogenous ethephon (ETH) and 1-methylcyclopropene (1-MCP). It was found that ETH treatment increased the soluble solids and anthocyanin content of the fruits, reduced hardness, and decreased organic acid content, while 1-MCP treatment inhibited these processes. Transcriptome analysis revealed that differentially expressed genes (DEGs) were enriched in the starch-sucrose metabolism pathway. qRT-PCR results further showed significant changes in the expression levels of sucrose metabolism genes, confirming the influence of ethylene signals on soluble sugar accumulation during strawberry fruit development. This study elucidates the quality changes and molecular mechanisms of ethylene signal in the development of strawberry fruits, providing some key targets and theoretical support for guiding strawberry cultivation and variety improvement.

Efeitos da variação da ploidia na expressão diferencial de genes em feijão-caupi

ABSTRACT: This study investigated the differences in gene expression profiles of diploid and autotetraploid in cowpea, and provided theoretical basis for screening key genes of differential expression and ploidy breeding. The phenotypes and contents of chlorophyll, soluble sugar and soluble protein of diploid and autotetraploid of cowpea were compared and transcriptome sequencing was performed. The autotetraploid leaves of cowpea were thicker and darker green than diploid leaves, and the contents of chlorophyll, soluble sugar and soluble protein in leaves were higher. A total of 2678 differentially expressed genes (DEGs) were analyzed in the diploid and autotetraploid of cowpea. Among them, there were 421 genes with higher expression of tetraploid than diploid, and 2257 genes with lower expression of tetraploid than diploid. All 2678 DEGs were annotated into the Gene Ontology (GO) functional library. The DEGs were mainly concentrated in metabolism and cell composition. Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway analysis showed that cowpea diploid and autotetraploid have significant differences in flavonoid biosynthesis, degradation of other glycan, phenylpropane biosynthesis, starch sucrose metabolism, keratin, amber and wax biosynthesis, circadian rhythm and plant pathways.

Transcriptomic analysis reveals the role of abscisic acid and ethylene in regulating starch-source biosynthesis associated with soft nose disorder in ‘Keitt’ mango fruit during postharvest

Soft nose is a physiological disorder in the distal flesh of mango fruit during ripening, which results in the decline in its consumer acceptance and salability. In this study, transcriptomic methods were used to compare mesocarp tissue from soft nose and healthy ‘Keitt’ mango fruit at different ripeness stages to identify the genes that are affected by soft nose disorder. The analysis revealed that the occurrence of soft nose affected plant hormone signaling pathways, particularly for abscisic acid (ABA) and ethylene. Also, accelerated starch decomposition and sucrose accumulation were found to be involved in development of soft nose disorder in mango fruit. Thus, soft nose fruit had lower contents of ABA and starch, and higher contents of sucrose, fructose, glucose and β-carotene compared to the healthy fruit. Also, we constructed a network of potential transcription factors and genes related to ABA and starch-sucrose metabolism that might be associated with soft nose disorder, and suggested that ABA might interact with ethylene to collectively regulate changes in downstream metabolic networks, thereby promoting development of soft nose disorder in ‘Keitt’ mango fruit during postharvest.

Transcriptome analysis of Populus × canadensis ‘Zhongliao1’ in response to low temperature stress

BackgroundLow temperatures are known to limit the growth and geographical distribution of poplars. Although some transcriptomic studies have been conducted to explore the response of poplar leaves to cold stress, only a few have comprehensively analyzed the effects of low temperature on the transcriptome of poplars and identified genes related to cold stress response and repair of freeze–thaw injury.ResultsWe exposed the Euramerican poplar Zhongliao1 to low temperatures; after stems were exposed to − 40℃, 4℃, and 20℃, the mixture of phloem and cambium was collected for transcriptome sequencing and bioinformatics analysis. A total of 29,060 genes were detected, including 28,739 known genes and 321 novel genes. Several differentially expressed genes (n = 36) were found to be involved in the Ca2+ signaling pathway, starch–sucrose metabolism pathway, abscisic acid signaling pathway, and DNA repair. They were functionally annotated; glucan endo-1,3-beta-glucosidase and UDP-glucuronosyltransferase genes, for instance, showed a close relationship with cold resistance. The expression of 11 differentially expressed genes was verified by qRT-PCR; RNA-Seq and qRT-PCR data were found to be consistent, which validated the robustness of our RNA-Seq findings. Finally, multiple sequence alignment and evolutionary analysis were performed, the results of which suggested a close association between several novel genes and cold resistance in Zhongliao1.ConclusionWe believe that the cold resistance and freeze–thaw injury repair genes identified in this study are of great significance for cold tolerance breeding.

Long-Term Soil Drought Limits Starch Accumulation by Altering Sucrose Transport and Starch Synthesis in Sweet Potato Tuberous Root.

In this study, the influences of long-term soil drought with three levels [soil-relative water content (SRWC) (75 ± 5)%, as the control; SRWC (55 ± 5)%, mild drought; SRWC (45 ± 5)%, severe drought] were investigated on sucrose-starch metabolism in sweet potato tuberous roots (TRs) by pot experiment. Compared to the control, drought stress increased soluble sugar and sucrose content by 4-60% and 9-75%, respectively, but reduced starch accumulation by 30-66% through decreasing the starch accumulate rate in TRs. In the drought-treated TRs, the inhibition of sucrose decomposition was attributed to the reduced activities of acid invertase (AI) and alkaline invertase (AKI) and the IbA-INV3 expression, rather than sucrose synthase (SuSy), consequently leading to the increased sucrose content in TRs. In addition, starch synthesis was inhibited mainly by reducing ADP-glucose pyrophosphorylase (AGPase), granular starch synthase (GBSS) and starch branching enzyme (SBE) activities in TRs under drought stress, and AGPase was the rate-limiting enzyme. Furthermore, soil drought remarkably up-regulated the IbSWEET11, IbSWEET605, and IbSUT4 expressions in Jishu 26 TRs, while it down-regulated or had no significant differences in Xushu 32 and Ningzishu 1 TRs. These results suggested that the sucrose-loading capability in Jishu 26 TRs were stronger than that in Xushu 32 and Ningzishu 1 TRs. Moreover, IbA-INV3, IbAGPS1, IbAGPS2, IbGBSSI and IbSBEII play important roles in different drought-tolerant cultivars under drought stress.

Combined analysis of multi-omics reveals the potential mechanism of flower color and aroma formation in Macadamia integrifolia.

Macadamia integrifolia Maiden & Betche is a domesticated high-value nut crop. The development of nut flower affects the fruit setting rate, yield and quality of nuts. Therefore, in this experiment, two varieties with different flower color, flowering time, flowering quantity and nut yield (single fruit weight) were selected as the research objects. Transcriptome (RNA-Seq) and metabolome (LC-MS/MS, GC-MS) analyses were performed to study the regulatory mechanisms of nut flower development, color and aroma. The results indicated that plant hormone signal transduction, starch sucrose metabolism, phenylpropanoid metabolism, flavonoid biosynthesis, and anthocyanin biosynthesis pathways were related to nut flower development and flower color formation. In the early stage of flowering, most of the differentially expressed genes (DEGs) are involved in the IAA signal transduction pathway, while in the later stage, the brassinolide signal pathway is mainly involved. In starch and sugar metabolism, DEGs are mainly involved in regulating and hydrolyzing stored starch into small molecular sugars in flower tissues. In the phenylpropanoid biosynthesis pathway, DEGs are mainly related to the color and aroma (volatile organic compounds, VOCs) formation of nut flowers. Four color formation metabolites (anthocyanins) in nut flowers were found by LC-MS/MS detection. In addition, the VOCs showed no significant difference between red nut flowers (R) and white nut flowers (W), which was mainly reflected in the aroma formation stage (flowering time). And 12 common differentially accumulation metabolites (DAMs) were detected by GC-MS and LC-MS/MS. At the same time, the DEGs, AAT, LOX and PAL genes, were also identified to regulate key metabolite synthesis during nut flower development. These genes were further verified by qRT-PCR. Our results provide insights to clarify the molecular mechanism of color and aroma formation during M. integrifolia flower development that pave the way for nut quality and yield breeding.

CmMYB44 might interact with CmAPS2-2 to regulate starch metabolism in oriental melon fruit

Sugar content is one of the determining factors for melon fruit maturity. Studies have shown that starch gradually degrades during fruit ripening, resulting in sugar accumulation. But the specific relationship between starch metabolism and sucrose accumulation was still unknown. Here, the starch and sugar contents, the activities of key enzymes and the expression patterns of genes related to starch-sucrose metabolism were determined in the fruit of high sugar and starch variety ‘HS’ and low sugar and starch variety ‘LW’. It was found that starch accumulated during fruit development process, and then degraded at 30 days after anthesis (DAA), which was synchronized with sucrose accumulation in ‘HS’ fruit, while starch and sucrose contents were always at a lower level during ‘LW’ fruit maturation. Furthermore, starch metabolism-related enzymes (Adenine dinucleotide phosphate -glucose pyrophosphorylase (AGPase), α-amylase (AMY), β-amylase (BMY)) and the key enzymes for sucrose accumulation (sucrose phosphate synthase (SPS) and sucrose synthase (SS)) were significantly increased at ripening stage of ‘HS’ fruit, and their activities were consistent with the expressions of CmAPS2-2, CmAMY2, CmBAM1, CmBAM9 and CmSPS1. However, the contents of starch and sucrose and the activities of AGPase and SPS in ‘LW’ fruit didn't change significantly. We discovered an R2R3-type MYB transcription factor, CmMYB44, screened from yeast one hybrid library, could directly bind to the promoter of CmAPS2-2 to inhibit its transcription. These results revealed that the targeted down-regulation of CmAPS2-2 by CmMYB44 might be involved in the starch accumulation process, which affect the flavor quality of oriental melon fruit.

Transcriptome analysis of walnut quality formation and color change mechanism of pellicle during walnut development

Walnuts (including those covered with a pellicle) are loved for their rich nutritional value. And the popular varieties of walnut cultivation are Juglans sigillata L. The pellicle (seed coat) of these walnut cultivars has different colors and has an indispensable influence on the walnut quality formation. However, there are few reports on the pellicle color and quality formation in different developmental stages of walnut (Juglans sigillata L.). Therefore, in this study, three walnut cultivars (F, Q, and T) with different pellicle colors were selected for transcriptome sequencing and physiological index analysis of the color and quality formation mechanisms at different development stages. The results showed that with the development of walnut fruit, the starch sucrose metabolism pathway in the pellicle was activated and promoted starch hydrolysis. Meanwhile, the expression levels of genes related to the alpha-linolenic acid metabolism pathway were significantly increased during walnut maturation, especially in F2. Some physiological indicators related to lipid oxidation were also detected and analyzed in this study, such as MDA, CAT, POD and DPPH. These results were similar to the expression patterns of corresponding regulatory genes in the RNA-Seq profile. In addition, lignin synthesis genes were up-regulated in the phenylpropanoid metabolic pathway, while key genes enriched in the flavonoid and anthocyanin synthesis pathways were down-regulated. The results were consistent with the results of total anthocyanins and flavonoid content detection during walnut development. Therefore, this experiment suggested that with the maturation of walnut pellicle, the gene expression in the phenylpropanoid metabolic pathway flowed to the branch of lignin synthesis, especially in the Q variety, resulting in lower flavonoid and anthocyanin content at the maturity stage than immature. This is also the main reason for the pale pellicle of the three walnut varieties after mature. The findings of this study showed that changes in the expression levels of regulating genes for lipid, starch, sugar, and flavonoid synthesis during walnut development influenced the accumulation of the related metabolite for walnut quality formation and pellicle color. The results of this experiment provided the molecular basis and reference for the breeding of high nutritional quality walnut varieties.

De novo transcriptome assembly of the cotyledon of Camellia oleifera for discovery of genes regulating seed germination

BackgroundCamellia oleifera (C.oleifera) is one of the most important wood oil species in the world. C.oleifera was propagated by nurse seedling grafting. Since the morphology of rootstocks has a significant impact on grafting efficiency and seedling quality, it is necessary to understand the molecular mechanism of morphogenesis for cultivating high-quality and controllable rootstocks. However, the genomic resource for this species is relatively limited, which hinders us from fully understanding the molecular mechanisms of seed germination in C.oleifera.ResultsIn this paper, using transcriptome sequencing, we measured the gene expression in the C.oleifera cotyledon in different stages of development and the global gene expression profiles. Approximately 45.4 gigabases (GB) of paired-end clean reads were assembled into 113,582 unigenes with an average length of 396 bp. Six public protein databases annotate 61.5% (68,217) of unigenes. We identified 11,391 differentially expressed genes (DEGs) throughout different stages of germination. Enrichment analysis revealed that DEGs were mainly involved in hormone signal transduction and starch sucrose metabolism pathways. The gravitropism regulator UNE10, the meristem regulators STM, KNAT1, PLT2, and root-specific transcription factor WOX11 all have higher gene expression levels in the CAM2 stage (seed soaking), which indicates that the cotyledon-regulated program for germination had initiated when the seeds were imbibition. Our data showed differentially reprogrammed to multiple hormone-related genes in cotyledons during C.oleifera seed germination.ConclusionCotyledons play vital roles, both as the main nutrient provider and as one primary instructor for seed germination and seedling growth. Together, our study will significantly enrich the genomic resources of Camellia and help us understand the molecular mechanisms of the development in the seed germination and seedling growth of C.oleifera. It is helpful to culture standard and superior quality rootstock for C.oleifera breeding.

Photosynthetic Carbon Fixation and Sucrose Metabolism Supplemented by Weighted Gene Co-expression Network Analysis in Response to Water Stress in Rice With Overlapping Growth Stages.

Drought stress at jointing and booting phases of plant development directly affects plant growth and productivity in rice. Limited by natural factors, the jointing and booting stages in rice varieties are known to overlap in high-latitude areas that are more sensitive to water deficit. However, the regulation of photosynthetic carbon fixation and sucrose metabolism in rice leaves under different degrees of drought stress remains unclear. In this study, rice plants were subjected to three degrees of drought stress (−10, −25, −and 40 kPa) for 15 days during the jointing-booting stage, we investigated photosynthetic carbon sequestration and sucrose metabolism pathways in rice leaves and analyzed key genes and regulatory networks using transcriptome sequencing in 2016. And we investigated the effects of drought stress on the growth periods of rice with overlapping growth periods in 2016 and 2017. The results showed that short-term drought stress promoted photosynthetic carbon fixation. However, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) activity significantly decreased, resulting in a significant decrease in photosynthetic rate. Drought stress increased the maximum activity of fructose-1,6-bisphosphate aldolase (FBA). FBA maintains the necessary photosynthetic rate during drought stress and provides a material base after the resumption of irrigation in the form of controlling the content of its reaction product triose phosphate. Drought stress significantly affected the activities of sucrose synthase (SuSase) and sucrose phosphate synthase (SPS). Vacuoles invertase (VIN) activity increased significantly, and the more severe the drought, the higher the VIN activity. Severe drought stress at the jointing-booting stage severely restricted the growth process of rice with overlapping growth stages and significantly delayed heading and anthesis stages. Transcriptome analysis showed that the number of differentially expressed genes was highest at 6–9 days after drought stress. Two invertase and four β-amylase genes with time-specific expression were involved in sucrose-starch metabolism in rice under drought stress. Combined with weighted gene co-expression network analysis, VIN and β-amylase genes up-regulated throughout drought stress were regulated by OsbZIP04 and OsWRKY62 transcription factors under drought stress. This study showed that any water deficit at the jointing-booting stage would have a serious effect on sucrose metabolism in leaves of rice with overlapping growth stages.

AMF species improve yielding potential of Cd stressed pigeonpea plants by modulating sucrose-starch metabolism, nutrients acquisition and soil microbial enzymatic activities

AMF species improve yielding potential of Cd stressed pigeonpea plants by modulating sucrose-starch metabolism, nutrients acquisition and soil microbial enzymatic activities

Transcriptomic and physiological analysis reveals interplay between salicylic acid and drought stress in citrus tree floral initiation.

Salicylic acid (SA) and drought stress promote more flowering in sweet orange. The physiological response and molecular mechanism underlying stress-induced floral initiation were discovered by transcriptome profiling. Numerous flowering-regulated genes were identified, and ectopically expressed CsLIP2A promotes early flowering in Arabidopsis. Floral initiation is a critical developmental mechanism associated with external factors, and citrus flowering is mainly regulated by drought stress. However, little is known about the intricate regulatory network involved in stress-induced flowering in citrus. To understand the molecular mechanism of floral initiation in citrus, flower induction was performed on potted Citrus sinensis trees under the combined treatment of salicylic acid (SA) and drought (DR). Physiological analysis revealed that SA treatment significantly normalized the drastic effect of drought stress by increasing antioxidant enzyme activities (SOD, POD, and CAT), relative leaf water content, total chlorophyll, and proline contents and promoting more flowering than drought treatment. Analysis of transcriptome changes in leaves from different treatments showed that 1135, 2728 and 957 differentially expressed genes (DEGs) were revealed in response to DR, SD (SA + DR), and SA (SA + well water) treatments in comparison with the well watered plants, respectively. A total of 2415, 2318 and 1933 DEGs were expressed in DR, SD, and SA in comparison with water recovery, respectively. Some key flowering genes were more highly expressed in SA-treated drought plants than in DR-treated plants. GO enrichment revealed that SA treatment enhances the regulation and growth of meristem activity under drought conditions, but no such a pathway was found to be highly enriched in the control. Furthermore, we focused on various hormones, sugars, starch metabolism, and biosynthesis-related genes. The KEGG analysis demonstrated that DEGs enriched in starch sucrose metabolism and hormonal signal transduction pathways probably account for stress-induced floral initiation in citrus. In addition, a citrus LIPOYLTRANSFERSAE 2A homologous (LIP2A) gene was upregulated by SD treatment. Ectopic expression of CsLIP2A exhibited early flowering in transgenic Arabidopsis. Taken together, this study provides new insight that contributes to citrus tree floral initiation under the SA-drought scenario as well as an excellent reference for stress-induced floral initiation in woody trees.

Emission control catalysts market worth $59.8 bn by 2026

MicroRNAs (miRNAs) are a new class of non-protein coding small RNAs that regulate gene expression at the post-transcriptional level in plants and animals. Although thousands of miRNAs were identified in many plant species, only 3 miRNAs have been reported in Lotus Japonicus, a model legume plant. In this study, 80 potential miRNA candidates were identified in 28 ESTs and 52 GSSs of L. japonicus using a homology-based computational analysis. A total of 735 miRNA targets were predicted and some of them encoded transcription factors as well as genes that function in stress response, signal transduction, methylation and others. Quantitative real-time PCR (qRT-PCR) analysis indicated that miR156a, miR160a and miR399a participated in seed germination of L. japonicus. GO and KEGG analysis suggested that the predicted miRNAs might target genes involved in lipid, nitrogen, starch sucrose metabolism and signal transduction.

Characterization and differential expression of sucrose and starch metabolism genes in contrasting chickpea (Cicer arietinum L.) genotypes under low temperature

Low temperature (LT) causes significant yield losses in chickpea (Cicer arietinum L.). The sucrose starch metabolism is associated with abiotic-stress tolerance or sensitivity in plants. The changes in sugars and starch contents under LT in chickpea have already been studied, however, no information is available on LT-induced alterations in transcription of carbohydrate metabolic pathway genes in chickpea. To understand the differences in the regulation of sucrose and starch metabolism under LT, the expression of sucrose and starch metabolism genes was studied in leaves of cold-sensitive (GPF2) and cold-tolerant (ICC 16349) chickpea genotypes. The mRNA sequences of chickpea genes were retrieved from the public databases followed by confirmation of identity and characterization. All the genes were functional in chickpea. Between the two paralogues of cell wall invertase, cell wall invertase 3×2 (CWINx2) was the truncated version of cell wall invertase 3×1 (CWINx1) with the loss of 241 bases in the mRNA and 67 amino acids at N terminal of the protein. Comparison of expression of the genes between control (22°C day / 16°C night) and LT treated (4°C; 72 h) plants revealed that granule bound starch synthase 2 (GBSS2) and β-amylase 3 (BAM3) were upregulated in ICC 16349 whereas sucrose phosphate synthase 2 (SPS2), CWINx1, CWINx2 and β-amylase 1 (BAM1) were downregulated. In contrast to this, SPS2, CWINx1, CWINx2 and BAM1 were upregulated and GBSS2 downregulated in GPF2 under LT. The gene expression data suggested that UGPase, CWINs, GBSS2 and BAM3 are important components of cold-tolerance machinery of chickpea.

Retraction Note: Cloning and characterization of TaPUB4, a U-box gene from common wheat (Triticum aestivum L.) involved in regulation of pollen development by influencing sucrose-starch pathway in anther

Development of functional pollen grains in plants is regulated through complex genetic networks and environmental clues. The ubiquitin-26S proteasome system is important in the post-translational modification of intracellular proteins, and the system includes the ubiquitin activating (E1), ubiquitin conjugating (E2), and ubiquitin ligase (E3) enzymes. Here, a novel plant U-box-containing cDNA was isolated in anther from common wheat (Triticum aestivum) and designed as TaPUB4. The cDNA encoding comprised 2598 bp, with an open reading frame of 865 amino acids. The deduced amino acid sequence of TaPUB4 showed 41.2–92.3% identity with other plant U-box homologous genes. Self-ubiquitination assay indicated that the bacterially expressed TaPUB4 protein had E3 ligase activity, and subcellular localization results showed that TaPUB4 was located in the nucleus and cytoplasm in onion epidermal cells. Overexpression of TaPUB4 gene in Arabidopsis atpub4 mutant restored partially the fertility of the mutant, increased the number of pollens in anthers, enhanced pollen viability, and displayed normal degradation of tapetum as anther development. The expression levels of genes related to starch deposition also changed greatly in the anthers of transgenic lines. These results support the notion that as a homolog of AtPUB4, TaPUB4 might control male fertility by regulating sucrose-starch metabolism in pollen grains, and this process may be accomplished through ubiquitin-proteasome system. The development and utilization of TaPUB4 as a functional molecular marker may be helpful for improving its fertility in wheat breeding programs in the future.

Proteomic analysis reveals that calcium channel blockers affect radicle protrusion during rice seed germination

Rice seed germination is regulated by numerous internal and external factors. Calcium ions (Ca2+), serving as an essential inorganic macronutrient and second messenger, are involved in the growth and development of plants. Calcium ions are predominantly stored in the cell wall and other organelles, such as vacuoles, mitochondria, and endoplasmic reticulum. Upon requirement, they are transferred from their storage location, where they are at high concentrations (mM), to the cytosol, where they are at lower concentrations (nM range). This study provides evidence that radicle protrusion is hindered in the presence of Ca2+ mobilization inhibitors during rice seed germination. A label-free quantification (LFQ) technique was used to investigate and characterize the importance of Ca2+ in rice seed germination through the suppression of their movement in the cell. After the extraction and digestion of total proteins, peptides were analyzed using nano-liquid chromatography (LC) coupled with tandem mass spectrometry (MS). A total of 667 proteins were significantly and differentially expressed under various treatments during rice seed germination. The functional analysis of these proteins indicated their involvement in various metabolic pathways, starch-sucrose metabolism, glycolysis-TCA, cadmium response, and other processes related to seed germination. Furthermore, the transcription levels of several calcium response genes were analyzed using quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and compared to the abundance of corresponding proteins. These results could aid in understanding the role of Ca2+ in rice seed germination.

Transcriptional changes during tomato ripening and influence of brackish water irrigation on fruit transcriptome and sugar content

Efficient management and utilization of brackish water irrigation help to minimize yield losses and promote fruit quality and sugar content in tomato fruit. However, the functional genes involved in sugar metabolic pathways and potential molecular pathways responsive to brackish water irrigation remain unknown. To this end, physiological responses and comparative transcriptional profiling was used to analyze the tomato fruit during the white-ripe period (CK1) and mature period (CK2) in plants grown under four water management strategies (rotating irrigation with brackish and fresh water during fruit development, T1; fresh water irrigation, T2; mixed brackish and fresh water irrigation, T3; mixed water and fresh water irrigation in sequence, T4). Comparative analysis revealed that during fruit development (CK2 cv CK1) differentially expressed genes (DEGs) involved in photosynthetic pathways and sucrose-starch metabolism were downregulated. However, two DEGs encoding putative beta-fructofuranosidases were significantly upregulated at the mature stage, which promoted the accumulation of glucose and fructose in CK2. Comparing four types of management strategies, rotating irrigation with brackish water and fresh water (T1) led to reprograming of global gene expression. Moreover, the upregulated DEGs in T1 were significantly enriched for signaling, hormone metabolism, and stress tolerance, suggesting the coordination of both stresses signaling as well as the plant hormone. These results provide a valuable reference for rational use of brackish water in the production of high-quality tomato in arid and semi-arid regions.

Regulation of carbon metabolism in two maize sister lines contrasted for chilling tolerance.

Maize can grow in cool temperate climates but is often exposed to spring chilling temperatures that can affect early seedling growth. Here, we used two sister double-haploid lines displaying a contrasted tolerance to chilling to identify major determinants of long-term chilling tolerance. The chilling-sensitive (CS) and the chilling-tolerant (CT) lines were grown at 14 °C day/10 °C night for 60 d. CS plants displayed a strong reduction in growth and aerial biomass compared with CT plants. Photosynthetic efficiency was affected with an increase in energy dissipation in both lines. Chilling tolerance in CT plants was associated with higher chlorophyll content, glucose-6-phosphate dehydrogenase activity, and higher sucrose to starch ratio. Few changes in cell wall composition were observed in both genotypes. There was no obvious correlation between nucleotide sugar content and cell wall polysaccharide composition. Our findings suggest that the central starch-sucrose metabolism is one major determinant of the response to low temperature, and its modulation accounts for the ability of CT plants to cope with low temperature. This modulation seemed to be linked to a strong alteration in the biosynthesis of nucleotide sugars that, at a high level, could reflect the remobilization of carbon in response to chilling.

Exploring regulatory networks in plants: transcription factors of starch metabolism.

Biological networks are complex (non-linear), redundant (cyclic) and compartmentalized at the subcellular level. Rational manipulation of plant metabolism may have failed due to inherent difficulties of a comprehensive understanding of regulatory loops. We first need to identify key factors controlling the regulatory loops of primary metabolism. The paradigms of plant networks are revised in order to highlight the differences between metabolic and transcriptional networks. Comparison between animal and plant transcription factors (TFs) reveal some important differences. Plant transcriptional networks function at a lower hierarchy compared to animal regulatory networks. Plant genomes contain more TFs than animal genomes, but plant proteins are smaller and have less domains as animal proteins which are often multifunctional. We briefly summarize mutant analysis and co-expression results pinpointing some TFs regulating starch enzymes in plants. Detailed information is provided about biochemical reactions, TFs and cis regulatory motifs involved in sucrose-starch metabolism, in both source and sink tissues. Examples about coordinated responses to hormones and environmental cues in different tissues and species are listed. Further advancements require combined data from single-cell transcriptomic and metabolomic approaches. Cell fractionation and subcellular inspection may provide valuable insights. We propose that shuffling of promoter elements might be a promising strategy to improve in the near future starch content, crop yield or food quality.

Abiotic Stress Responsive miRNA-Target Network and Related Markers (SNP, SSR) in Brassica juncea.

Abiotic stress is one of the major factors responsible for huge yield loss in crop plants. MicroRNAs play a key role in adaptive responses of plants under abiotic stress conditions through post-transcriptional gene regulations. In present study, 95 potential miRNAs were predicted in Brassica juncea using comparative genomics approach. It was noted that these miRNAs, target several transcription factors (TFs), transporter family proteins, signaling related genes, and protease encoding genes. Nineteen distinct miRNA-target regulatory networks were observed with significant involvement in regulation of transcription, response to stimulus, hormone and auxin mediated signaling pathway related gene ontology (GO) term. The sucrose-starch metabolism and pentose-gluconate interconversion pathways were found significantly enriched for these target genes. Molecular markers such as Simple Sequence Repeats (SSR) and Single Nucleotide Polymorphism (SNPs) were identified on miRNAs (miR-SSRs and miR-SNPs) and their target genes in B. juncea. Notably, one of the miR-SNP (C/T) was found at the 5th position on mature region of miR2926. This C/T transition led to the distorted and unstable hairpin structure of miR2926, consequently complete loss of target function. Hence, findings from this study will lay a foundation for marker assisted breeding for abiotic stress tolerant varieties of B. juncea.