Overexpression of the anaphase-promoting complex (APC) genes in Nicotiana tabacum promotes increasing biomass accumulation

Unlocking the molecular basis of wheat straw composition and morphological traits through multi-locus GWAS

BACKGROUND

Rapid reductions in emissions from fossil fuel burning are needed to curb global climate change. Biofuel production from crop residues can contribute to reducing the energy crisis and environmental deterioration. Wheat is a renewable source for biofuels owing to the low cost and high availability of its residues. Thus, identifying candidate genes controlling these traits is pivotal for efficient biofuel production. Here, six multi-locus genome-wide association (ML-GWAS) models were applied using 185 tetraploid wheat accessions to detect quantitative trait nucleotides (QTNs) for fifteen traits associated with biomass composition.

RESULTS

Among the 470 QTNs, only 72 identified by at least two models were considered as reliable. Among these latter, 16 also showed a significant effect on the corresponding trait (p.value < 0.05). Candidate genes survey carried out within 4 Mb flanking the QTNs, revealed putative biological functions associated with lipid transfer and metabolism, cell wall modifications, cell cycle, and photosynthesis. Four genes encoded as Cellulose Synthase (CeSa), Anaphase promoting complex (APC/C), Glucoronoxylan 4-O Methyltransferase (GXM) and HYPONASTIC LEAVES1 (HYL1) might be responsible for an increase in cellulose, and natural and acid detergent fiber (NDF and ADF) content in tetraploid wheat. In addition, the SNP marker RFL_Contig3228_2154 associated with the variation in stem solidness (Q.Scsb-3B) was validated through two molecular methods (High resolution melting; HRM and RNase H²-dependent PCR; rhAMP).

CONCLUSIONS

The study provides new insights into the genetic basis of biomass composition traits on tetraploid wheat. The application of six ML-GWAS models on a panel of diverse wheat genotypes represents an efficient approach to dissect complex traits with low heritability such as wheat straw composition. The discovery of genes/genomic regions associated with biomass production and straw quality parameters is expected to accelerate the development of high-yielding wheat varieties useful for biofuel production.

The role of APC/C in cell cycle dynamics, growth and development in cereal crops

Cereal crops can be considered the basis of human civilization. Thus, it is not surprising that these crops are grown in larger quantities worldwide than any other food supply and provide more energy to humankind than any other provision. Additionally, attempts to harness biomass consumption continue to increase to meet human energy needs. The high pressures for energy will determine the demand for crop plants as resources for biofuel, heat, and electricity. Thus, the search for plant traits associated with genetic increases in yield is mandatory. In multicellular organisms, including plants, growth and development are driven by cell division. These processes require a sequence of intricated events that are carried out by various protein complexes and molecules that act punctually throughout the cycle. Temporal controlled degradation of key cell division proteins ensures a correct onset of the different cell cycle phases and exit from the cell division program. Considering the cell cycle, the Anaphase-Promoting Complex/Cyclosome (APC/C) is an important conserved multi-subunit ubiquitin ligase, marking targets for degradation by the 26S proteasome. Studies on plant APC/C subunits and activators, mainly in the model plant Arabidopsis, revealed that they play a pivotal role in several developmental processes during growth. However, little is known about the role of APC/C in cereal crops. Here, we discuss the current understanding of the APC/C controlling cereal crop development.

Comparative selective signature analysis and high-resolution GWAS reveal a new candidate gene controlling seed weight in soybean

KEY MESSAGE

We detected a QTL qHSW-16 undergone strong selection associated with seed weight and identified a novel candidate gene controlling seed weight candidate gene for this major QTL by qRT-PCT. Soybean [Glycine max (L.) Merr.] provides more than half of the world's oilseed production. To expand its germplasm resources useful for breeding increased yield and oil quality cultivars, it is necessary to resolve the diversity and evolutionary history of this crop. In this work, we resequenced 283 soybean accessions from China and obtained a large number of high-quality SNPs for investigation of the population genetics that underpin variation in seed weight and other agronomic traits. Selective signature analysis detected 78 (~ 25.0 Mb) and 39 (~ 22.60 Mb) novel putative selective signals that were selected during soybean domestication and improvement, respectively. Genome-wide association study (GWAS) identified five loci associated with seed weight. Among these QTLs, qHSW-16, overlapped with the improvement-selective region on chromosome 16, suggesting that this QTL may be underwent strong selection during soybean improvement. Of the 18 candidate genes in qHSW-16, only SoyZH13_16G122400 showed higher expression levels in a large seed variety compared to a small seed variety during seed development. These results identify SoyZH13_16G122400 as a novel candidate gene controlling seed weight and provide foundational insights into the molecular targets for breeding improvement of seed weight and potential seed yield in soybean.

At-CycD2 Enhances Accumulation of Above-Ground Biomass and Recombinant Proteins in Transgenic Nicotiana benthamiana Plants

Transient expression in Nicotiana benthamiana holds great potential for recombinant protein manufacturing due to its advantages in terms of speed and yield compared to stably transformed plants. To continue improving the quantity of recombinant proteins the plant host will need to be modified at both plant and cellular levels. In attempt to increase leaf mass fraction, we transformed N. benthamiana with the At-CycD2 gene, a positive regulator of the cell cycle. Phenotypic characterization of the T₁ progeny plants revealed their accelerated above-ground biomass accumulation and enhanced rate of leaf initiation. In comparison to non-transgenic control the best performing line At-CycD2-15 provided 143 and 140% higher leaf and stem biomass fractions, respectively. The leaf area enlargement of the At-CycD2-15 genotype was associated with the increase of epidermal cell number compensated by slightly reduced cell size. The production capacity of the At-CycD2-15 transgenic line was superior to that of the non-transgenic N. benthamiana. The accumulation of transiently expressed GFP and scFv-TM43-E10 proteins per unit biomass was increased by 138.5 and 156.7%, respectively, compared to the wild type. With these results we demonstrate the potential of cell cycle regulator gene At-CycD2 to modulate both plant phenotype and intracellular environment of N. benthamiana for enhanced recombinant protein yield.

Deciphering the biological processes underlying tomato biomass production and composition

The huge amounts of biomass residues, remaining in the field after tomato fruits harvesting, can be utilized to produce bioenergy. A multiple level approach aimed to characterize two Solanum pennellii introgression lines (ILs), with contrasting phenotypes for plant architecture and biomass was carried out. The study of gene expression dynamics, microscopy cell traits and qualitative and quantitative cell wall chemical compounds variation enabled the discovery of key genes and cell processes involved biomass accumulation and composition. Enhanced biomass production observed in IL2-6 line is due to a more effective coordination of chloroplasts and mitochondria energy fluxes. Microscopy analysis revealed a higher number of cells and chloroplasts in leaf epidermis in the high biomass line whilst chemical measurements on the two lines pointed out striking differences in the cell wall composition and organization. Taken together, our findings shed light on the mechanisms underlying the tomato biomass production and processability.

Non-plastidial expression of a synthetic insect geranyl pyrophosphate synthase effectively increases tobacco plant biomass

Designing effective synthetic genes of interest is a fundamental step in plant synthetic biology for biomass. Geranyl pyrophosphate (diphosphate) synthase (GPPS) catalyzes a bottleneck step toward terpenoid metabolism. We previously designed and synthesized a plant (Arabidopsis thaliana)-insect (Myzus persicae, Mp) GPPS- human influenza hemagglutinin (HA) cDNA, namely PTP-MpGPPS-HA (or PTP-sMpGPPS-HA, s: synthetic), to localize the protein in plastids and improve plant biomass. To better understand the effects of different subcellular localizations on plant performance, herein we report PTP-sMpGPPS-HA re-design to synthesize a new MpGPPS-HA cDNA, namely sMpGPPS-HA, to express a non-plastidial sMpGPPS-HA protein. The sMpGPPS-HA cDNA driven by a 2 × S 35S promoter was introduced into Nicotiana tabacum Xanthi. PTP-MpGPPS-HA and PMDC84 vector transgenic plants were also generated as positive and negative controls, respectively. Eighteen to twenty transgenic T0 lines were generated for each sMpGPPS-HA, PTP-sMpGPPS-HA, and PMDC84. Transcriptional genotyping analysis demonstrated the expression of sMpGPPS-HA in transgenic plants. Confocal microscopy analysis of transgenic progeny demonstrated the non-plastidial localization of sMpGPPS-HA. Growth of T1 transgenic and wild-type control plants showed that the expression of sMpGPPS-HA effectively increased plant height by 50-80%, leaf numbers and sizes, and dry biomass by 60-80%. Calculation of the vegetative growth rates showed that the expression of sMpGPPS-HA increased plant height each week. Moreover, sMpGPPS-HA expression promoted early flowering and reduced leaf carotenoid levels. In conclusion, non-plastidial expression of the novel sMpGPPS-HA was effective for improving tobacco growth and biomass. Our data indicate that research examining different subcellular localizations facilitates a better understanding of in planta functions of proteins encoded by synthetic cDNAs.