Overexpression of PsnSuSy1, 2 genes enhances secondary cell wall thickening, vegetative growth, and mechanical strength in transgenic tobacco

SlMES1 modulates methyl salicylate to influence fruit volatile profiles in tomato

Methyl salicylate (MeSA), known as phloem-based mobile signal, has been identified as undesirable volatile compounds for tomato fruits due to its medicinal and wintergreen aroma properties. However, the response of most volatile compounds to endogenous MeSA are still unclarified. In this work, we found the concentration of MeSA can be regulated by salicylic acid methyl esterase 1 (SlMES1). We used CRISPR/Cas9 and GC-MS strategies to investigate the effect of SlMES1 on the biosynthesis of flavor compounds during tomato fruit ripening. Our results showed that the loss of function of SlMES1 significantly increased the MeSA content by altering the flux of MeSA and SA interconversion. Although the increased endogenous MeSA did not affect the fruit ripening process, it altered the concentration and proportion of fruit volatiles, mainly reducing the concentration of soluble sugar and volatile substances derived from amino acids and carotenoids. Additionally, the reduction of soluble sugars and volatiles was associated with downregulated the gene encoding Sucrose synthase (SuSy), Alcohol dehydrogenase (ADH), Phenylalanine ammonia lyase (PAL), and β - Carotene hydroxylase (CHY-β) when compared with control. Taken together, SlMES1 plays a crucial role in regulating the MeSA content during fruit ripening and could become a breeding target for improving fruit flavor quality.

Sucrose synthase: An enzyme with multiple roles in plant physiology

Sucrose synthase (SuS) is a key enzyme in the regulation of sucrose metabolism in plants and participates in the reversible reaction of sucrose conversion to uridine diphosphate-glucose and fructose. It plays an important role in promoting taproot development, starch synthesis, cellulose synthesis, improving plant nitrogen fixation capacity, sugar metabolism, and fruit and seed development. Recent studies have shown that SuS responds to abiotic stresses such as drought stress, cold stress and waterlogging stress, especially in waterlogging stress. This paper provides a comprehensive review on the basic properties, physiological functions, and signal transduction pathways of SuS, aiming to establish a theoretical foundation for its further research.

Role of Actin Dynamics and GhACTIN1 Gene in Cotton Fiber Development: A Prototypical Cell for Study

Cotton crop is considered valuable for its fiber and seed oil. Cotton fiber is a single-celled outgrowth from the ovule epidermis, and it is a very dynamic cell for study. It has four distinct but overlapping developmental stages: initiation, elongation, secondary cell wall synthesis, and maturation. Among the various qualitative characteristics of cotton fiber, the important ones are the cotton fiber staple length, tensile strength, micronaire values, and fiber maturity. Actin dynamics are known to play an important role in fiber elongation and maturation. The current review gives an insight into the cotton fiber developmental stages, the qualitative traits associated with cotton fiber, and the set of genes involved in regulating these developmental stages and fiber traits. This review also highlights some prospects for how biotechnological approaches can improve cotton fiber quality.

Genome-Wide Identification and Analysis of Stress Response of Trehalose-6-Phosphate Synthase and Trehalose-6-Phosphate Phosphatase Genes in Quinoa

Saline-alkali stress seriously affects the yield and quality of crops, threatening food security and ecological security. Improving saline-alkali land and increasing effective cultivated land are conducive to sustainable agricultural development. Trehalose, a nonreducing disaccharide, is closely related to plant growth and development and stress response. Trehalose 6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP) are key enzymes catalyzing trehalose biosynthesis. To elucidate the effects of long-term saline-alkali stress on trehalose synthesis and metabolism, we conducted an integrated transcriptome and metabolome analysis. As a result, 13 TPS and 11 TPP genes were identified in quinoa (Chenopodium quinoa Willd.) and were named CqTPS1-13 and CqTPP1-11 according to the order of their Gene IDs. Through phylogenetic analysis, the CqTPS family is divided into two classes, and the CqTPP family is divided into three classes. Analyses of physicochemical properties, gene structures, conservative domains and motifs in the proteins, and cis-regulatory elements, as well as evolutionary relationships, indicate that the TPS and TPP family characteristics are highly conserved in quinoa. Transcriptome and metabolome analyses of the sucrose and starch metabolism pathway in leaves undergoing saline-alkali stress indicate that CqTPP and Class II CqTPS genes are involved in the stress response. Moreover, the accumulation of some metabolites and the expression of many regulatory genes in the trehalose biosynthesis pathway changed significantly, suggesting the metabolic process is important for the saline-alkali stress response in quinoa.

Recent advances in metabolic engineering of microorganisms for advancing lignocellulose-derived biofuels

Combating climate change and ensuring energy supply to a rapidly growing global population has highlighted the need to replace petroleum fuels with clean, and sustainable renewable fuels. Biofuels offer a solution to safeguard energy security with reduced ecological footprint and process economics. Over the past years, lignocellulosic biomass has become the most preferred raw material for the production of biofuels, such as fuel, alcohol, biodiesel, and biohydrogen. However, the cost-effective conversion of lignocellulose into biofuels remains an unsolved challenge at the industrial scale. Recently, intensive efforts have been made in lignocellulose feedstock and microbial engineering to address this problem. By improving the biological pathways leading to the polysaccharide, lignin, and lipid biosynthesis, limited success has been achieved, and still needs to improve sustainable biofuel production. Impressive success is being achieved by the retouring metabolic pathways of different microbial hosts. Several robust phenotypes, mostly from bacteria and yeast domains, have been successfully constructed with improved substrate spectrum, product yield and sturdiness against hydrolysate toxins. Cyanobacteria is also being explored for metabolic advancement in recent years, however, it also remained underdeveloped to generate commercialized biofuels. The bacterium Escherichia coli and yeast Saccharomyces cerevisiae strains are also being engineered to have cell surfaces displaying hydrolytic enzymes, which holds much promise for near-term scale-up and biorefinery use. Looking forward, future advances to achieve economically feasible production of lignocellulosic-based biofuels with special focus on designing more efficient metabolic pathways coupled with screening, and engineering of novel enzymes.

Identification and expression analysis of the sucrose synthase gene family in pomegranate (Punica granatum L.)

BACKGROUND

Sucrose synthase (SUS, EC 2.4.1.13) is one of the major enzymes of sucrose metabolism in higher plants. It has been associated with C allocation, biomass accumulation, and sink strength. The SUS gene families have been broadly explored and characterized in a number of plants. The pomegranate (Punica granatum) genome is known, however, it lacks a comprehensive study on its SUS genes family.

METHODS

PgSUS genes were identified from the pomegranate genome using a genome-wide search method. The PgSUS gene family was comprehensively analyzed by physicochemical properties, evolutionary relationship, gene structure, conserved motifs and domains, protein structure, syntenic relationships, and cis-acting elements using bioinformatics methods. The expression pattern of the PgSUS gene in different organs and fruit development stages were assayed with RNA-seq obtained from the NCBI SRA database as well as real-time quantitative polymerase chain reaction (qPCR).

RESULTS

Five pomegranate SUS genes, located on four different chromosomes, were divided into three subgroupsaccording to the classification of other seven species. The PgSUS family was found to be highly conserved during evolution after studying the gene structure, motifs, and domain analysis. Furthermore, the predicted PgSUS proteins showed similar secondary and tertiary structures. Syntenic analysis demonstrated that four PgSUS genes showed syntenic relationships with four species, with the exception of PgSUS2. Predictive promoter analysis indicated that PgSUS genes may be responsive to light, hormone signaling, and stress stimulation. RNA-seq analysis revealed that PgSUS1/3/4 were highly expressed in sink organs, including the root, flower, and fruit, and particularly in the outer seed coats. qPCR analysis showed also that PgSUS1, PgSUS3, and PgSUS4 were remarkably expressed during fruit seed coat development. Our results provide a systematic overview of the PgSUS gene family in pomegranate, developing the framework for further research and use of functional PgSUS genes.

Recent advances in lignocellulosic biomass for biofuels and value-added bioproducts - A critical review

Lignocellulosic biomass is a highly renewable, economical, and carbon-neutral feedstock containing sugar-rich moieties that can be processed to produce second-generation biofuels and bio-sourced compounds. However, due to their heterogeneous multi-scale structure, the lignocellulosic materials have major limitations to valorization and exhibit recalcitrance to saccharification or hydrolysis by enzymes. In this context, this review focuses on the latest methods available and state-of-the-art technologies in the pretreatment of lignocellulosic biomass, which aids the disintegration of the complex materials into monomeric units. In addition, this review deals with the genetic engineering techniques to develop advanced strategies for fermentation processes or microbial cell factories to generate desired products in native or modified hosts. Further, it also intends to bridge the gap in developing various economically feasible lignocellulosic products and chemicals using biorefining technologies.

MdFRK2-mediated sugar metabolism accelerates cellulose accumulation in apple and poplar

BACKGROUND

Cellulose is not only a common component in vascular plants, but also has great economic benefits for paper, wood, and industrial products. In addition, its biosynthesis is highly regulated by carbohydrate metabolism and allocation in plant. MdFRK2, which encodes a key fructokinase (FRK) in apple, showed especially high affinity to fructose and regulated carbohydrate metabolism.

RESULTS

It was observed that overexpression of MdFRK2 in apple decreased sucrose (Suc) and fructose (Fru) with augmented FRK activity in stems, and caused the alterations of many phenotypic traits that include increased cellulose content and an increase in thickness of the phloem region. To further investigate the involved mechanisms, we generated FRK2-OE poplar lines OE#1, OE#4 and OE#9 and discovered (1) that overexpression of MdFRK2 resulted in the huge increased cellulose level by shifting the fructose 6-phosphate or glucose 6-phsophate towards UDPG formation, (2) a direct metabolic pathway for the biosynthesis of cellulose is that increased cleavage of Suc into UDP-glucose (UDPG) for cellulose synthesis via the increased sucrose synthase (SUSY) activity and transcript levels of PtrSUSY1, (3) that the increased FRK activity increases the sink strength overall so there is more carbohydrate available to fuel increased cambial activity and that resulted in more secondary phloem. These results demonstrated that MdFRK2 overexpression would significantly changes the photosynthetic carbon flux from sucrose and hexose to UDPG for increased cellulose synthesis.

CONCLUSIONS

The present data indicated that MdFRK2 overexpression in apple and poplar changes the photosynthetic carbon flux from sucrose and hexose to UDPG for stem cellulose synthesis. A strategy is proposed to increase cellulose production by regulating sugar metabolism as a whole.

DNA methylation and its effects on gene expression during primary to secondary growth in poplar stems

Background

As an important epigenetic mark, 5-methylcytosine (5mC) methylation is involved in many DNA-dependent biological processes and plays a role during development and differentiation of multicellular organisms. However, there is still a lack of knowledge about the dynamic aspects and the roles of global 5mC methylation in wood formation in tree trunks. In this study, we not only scrutinized single-base resolution methylomes of primary stems (PS), transitional stems (TS), and secondary stems (SS) of Populus trichocarpa using a high-throughput bisulfite sequencing technique, but also analyzed the effects of 5mC methylation on the expression of genes involved in wood formation.

Results

The overall average percentages of CG, CHG, and CHH methylation in poplar stems were ~ 53.6%, ~ 37.7%, and ~ 8.5%, respectively, and the differences of 5mC in genome-wide CG/CHG/CHH contexts among PS, TS, and SS were statistically significant (p < 0.05). The evident differences in CG, CHG, and CHH methylation contexts among 2 kb proximal promoters, gene bodies, and 2 kb downstream regions were observed among PS, TS, and SS. Further analysis revealed a perceptible global correlation between 5mC methylation levels of gene bodies and transcript levels but failed to reveal a correlation between 5mC methylation levels of proximal promoter regions and transcript levels. We identified 653 and 858 DMGs and 4978 and 4780 DEGs in PS vs TS and TS vs SS comparisons, respectively. Only 113 genes of 653 DMGs and 4978 DEGs, and 114 genes of 858 DMGs and 4780 DEG were common. Counterparts of some of these common genes in other species, including Arabidopsis thaliana, are known to be involved in secondary cell wall biosynthesis and hormone signaling. This indicates that methylation may directly modulate wood formation genes and indirectly attune hormone signaling genes, which in turn impact wood formation.

Conclusions

DNA methylation only marginally affects pathway genes or regulators involved in wood formation, suggesting that further studies of wood formation should lean towards the indirect effects of methylation. The information and data we provide here will be instrumental for understanding the roles of methylation in wood formation in tree species.

Engineering of Bioenergy Crops: Dominant Genetic Approaches to Improve Polysaccharide Properties and Composition in Biomass

Large-scale, sustainable production of lignocellulosic bioenergy from biomass will depend on a variety of dedicated bioenergy crops. Despite their great genetic diversity, prospective bioenergy crops share many similarities in the polysaccharide composition of their cell walls, and the changes needed to optimize them for conversion are largely universal. Therefore, biomass modification strategies that do not depend on genetic background or require mutant varieties are extremely valuable. Due to their preferential fermentation and conversion by microorganisms downstream, the ideal bioenergy crop should contain a high proportion of C6-sugars in polysaccharides like cellulose, callose, galactan, and mixed-linkage glucans. In addition, the biomass should be reduced in inhibitors of fermentation like pentoses and acetate. Finally, the overall complexity of the plant cell wall should be modified to reduce its recalcitrance to enzymatic deconstruction in ways that do no compromise plant health or come at a yield penalty. This review will focus on progress in the use of a variety of genetically dominant strategies to reach these ideals. Due to the breadth and volume of research in the field of lignin bioengineering, this review will instead focus on approaches to improve polysaccharide component plant biomass. Carbohydrate content can be dramatically increased by transgenic overexpression of enzymes involved in cell wall polysaccharide biosynthesis. Additionally, the recalcitrance of the cell wall can be reduced via the overexpression of native or non-native carbohydrate active enzymes like glycosyl hydrolases or carbohydrate esterases. Some research in this area has focused on engineering plants that accumulate cell wall-degrading enzymes that are sequestered to organelles or only active at very high temperatures. The rationale being that, in order to avoid potential negative effects of cell wall modification during plant growth, the enzymes could be activated post-harvest, and post-maturation of the cell wall. A potentially significant limitation of this approach is that at harvest, the cell wall is heavily lignified, making the substrates for these enzymes inaccessible and their activity ineffective. Therefore, this review will only include research employing enzymes that are at least partially active under the ambient conditions of plant growth and cell wall development.