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植物學頂尖雜誌 Plant Cell, New Phytol , Mol Plant, Plant Physiol, Plant Biotechnol J, Plant J, nature Plants及綜合期刊Nucleic Acids Res. ， PNAS，NB，NC及NG有關植物學的研究文章導讀，每日定時更新，了解行業最前沿進展。
Specialized secondary metabolites serve not only to protect plants against abiotic and biotic challenges, but have also been used extensively by humans to combat diseases. Due to the importance of medicinal plants for health, we need to find new and sustainable ways to produce their specialized metabolites. In addition to direct extraction, recent progress in metabolic engineering of plants offers alternative supply options. We argue that metabolic engineering for the production of some secondary metabolites in plants may have distinct advantages over microbial production platforms and we propose new approaches to plant metabolic engineering, inspired by an ancient Chinese irrigation system. Metabolic engineering strategies work at three levels; introducing biosynthetic genes, use of transcription factors (TFs), and improvement of metabolic flux including increasing the supply of precursors, energy and reducing power. In addition, recent progress in biotechnology can contribute to markedly better engineering, such as the use of specific promoters, and the deletion of competing branch pathways. We suggest that next generation plant metabolic engineering will improve current engineering strategies, for the purpose of producing valuable metabolites in plants, on industrial scales.
http://www.cell.com/molecular-plant/abstract/S1674-2052(17)30246-0
Temperature influences the distribution, range and phenology of plants. The key transcriptional activators of the heat shock response in eukaryotes, the heat shock factors (HSFs), have undergone a large-scale gene amplification in plants. While HSFs are central in heat stress responses, their role in ambient temperature changes is less well understood. We show here that the warm ambient temperature transcriptome is dependent upon the HSFA1 clade of Arabidopsis HSFs, which cause a rapid and dynamic eviction of H2A.Z-nucleosomes at target genes. A transcriptional cascade results in the activation of multiple downstream stress responsive transcription factors, triggering large-scale changes to the transcriptome in response to elevated temperature. H2A.Z-nucleosomes are enriched at temperature responsive genes at non-inducible temperature, and thus likely confer inducibility of gene expression and higher responsive dynamics. We propose that the antagonistic effects of H2A.Z and HSF1 provide a mechanism to activate gene expression rapidly and precisely in response to temperature, while preventing leaky transcription in the absence of an activation signal.
http://www.cell.com/molecular-plant/abstract/S1674-2052(17)30245-9
No abstract
http://www.cell.com/molecular-plant/fulltext/S1674-2052(17)30244-7
Root growth is modulated by environmental factors and depends on cell production in the root meristem (RM). New cells in the meristem are generated by stem cells and transit-amplifying cells, which together determine RM cell number. Transcription factors and chromatin-remodelling factors have been implicated in regulating the switch from stem cells to transit-amplifying cells. Here we show that two Arabidopsis thaliana paralogs encoding plant-specific histone deacetylases, HDT1 and HDT2, regulate a second switch from transit-amplifying cells to expanding cells. Knockdown of HDT½ (hdt1,2i) results in an earlier switch and causes a reduced RM cell number. Our data show that HDT½ negatively regulate the acetylation level of the C19-GIBBERELLIN 2-OXIDASE 2 (GA2ox2) locus and repress the expression of GA2ox2 in the RM and elongation zone. Overexpression of GA2ox2 in the RM phenocopies the hdt1,2i phenotype. Conversely, knockout of GA2ox2 partially rescues the root growth defect of hdt1,2i. These results suggest that by repressing the expression of GA2ox2, HDT½ likely fine-tune gibberellin metabolism and they are crucial for regulating the switch from cell division to expansion to determine RM cell number. We propose that HDT½ function as part of a mechanism that modulates root growth in response to environmental factors.
http://www.plantcell.org/content/early/2017/09/08/tpc.17.00366
Phosphoenolpyruvate carboxylase (PPC; EC 4.1.1.31) catalyzes primary nocturnal CO2 fixation in Crassulacean acid metabolism (CAM) species. CAM PPC is regulated post-translationally by a circadian clock controlled protein kinase called phosphoenolpyruvate carboxylase kinase (PPCK). PPCK phosphorylates PPC during the dark period, reducing its sensitivity to feedback inhibition by malate, and thus enhancing nocturnal CO2 fixation to stored malate. Here, we report the generation and characterization of transgenic RNAi lines of the obligate CAM species Kalanchoë fedtschenkoi with reduced levels of KfPPCK1 transcripts. Plants with reduced or no detectable dark phosphorylation of PPC displayed up to a 66% reduction in total dark period CO2 fixation. These perturbations paralleled reduced malate accumulation at dawn and decreased nocturnal starch turnover. Loss of oscillations in the transcript abundance of KfPPCK1 was accompanied by a loss of oscillations in the transcript abundance of many core circadian clock genes, suggesting that perturbing the only known link between CAM and the circadian clock feeds back to perturb the central circadian clock itself. This work shows that clock control of KfPPCK1 prolongs the activity of PPC throughout the dark period in K. fedtschenkoi, optimizing CAM-associated dark CO2 fixation, malate accumulation, CAM productivity and core circadian clock robustness.
http://www.plantcell.org/content/early/2017/09/08/tpc.17.00301
No abstract
http://www.plantcell.org/content/early/2017/09/08/tpc.17.00709
Nitrate uptake by plant cells requires both high and low-affinity transport activities. Arabidopsis (Arabidopsis thaliana, At) nitrate transporter 1/peptide transporter family (NPF) 6.3 is a dual-affinity plasma membrane transport protein that has both high and low-affinity functions. At-NPF6.3 imports and senses nitrate and is regulated by phosphorylation at Thr-101 (T101). A detailed functional analysis of two maize (Zea mays, Zm) homologs of At-NPF6.3 (Zm-NPF6.6 and Zm-NPF6.4) showed that Zm-NPF6.6 was a pH dependent non-biphasic high-affinity nitrate-specific transport protein. By contrast, maize NPF6.4 was a low-affinity nitrate transporter with efflux activity. When supplied chloride, NPF6.4 switched to a high-affinity chloride selective transporter, while NPF6.6 had only a low-affinity chloride transport activity. Structural predictions identified a nitrate binding His (H362) in NPF6.6 but not in NPF6.4. Mutation of NPF6.4 Tyr-370 to His (Y370H) resulted in saturable high-affinity nitrate transport activity and nitrate selectivity. Loss of H362 in NPF6.6 (H362Y) eliminated both nitrate and chloride transport. Furthermore, alterations to Thr-104, a conserved phosphorylation site in NPF6.6, resulted in a similar high-affinity nitrate transport activity with increased Km whereas equivalent changes in NPF6.4 (T106) disrupted high-affinity chloride transport activity. NPF6 proteins exhibit different substrate specificity in plants and regulate nitrate transport affinity/selectivity using a conserved His residue.
http://www.plantcell.org/content/early/2017/09/08/tpc.16.00724
Long non-coding RNAs (lncRNAs) affect gene expression through a wide range of mechanisms and are considered as important regulators in many essential biological processes. A large number of lncRNA transcripts have been predicted or identified in plants in recent years. However, the biological functions for most of them are still unknown. In this study, we identified an Arabidopsis thaliana lncRNA, Drought induced RNA (DRIR), as a novel positive regulator of plant response to drought and salt stress. DRIR was expressed at a low level under non-stress conditions but can be significantly activated by drought and salt stress as well as by abscisic acid (ABA) treatment. We identified a T-DNA insertion mutant, drirD, which had higher expression of the DRIR gene than the wild type plants. The drirD mutant exhibits increased tolerance to drought and salt stress. Overexpressing DRIR in Arabidopsis also increased tolerance to drought and salt stress of the transgenic plants. The drirD mutant and the overexpressing seedlings are more sensitive to ABA than the wild type in stomata closure and seedling growth. Genome-wide transcriptome analysis demonstrated that the expression of a large number of genes was altered in drirD and the overexpressing plants. These include genes involved in ABA signaling, water transport and other stress-relief processes. Our study reveals a mechanism whereby DRIR regulates plant response to abiotic stress by modulating the expression of a series of genes involved in stress response.
http://www.plantphysiol.org/content/early/2017/09/08/pp.17.00574
Unknown mechanisms tightly regulate the basal activity of the wound-inducible defence mediator jasmonate (JA) in undamaged tissues. However, the Arabidopsis fatty acid oxygenation upregulated2(fou2) mutant in vacuolar two-pore channel 1 (TPC1D454N) displays high JA pathway activity in undamaged leaves. This mutant was used to explore mechanisms controlling basal JA pathway regulation.fou2 was re-mutated to generate novel 『ouf』 suppressor mutants. Patch-clamping was used to examine TPC1 cation channel characteristics in the ouf suppressor mutants and in fou2. Calcium (Ca2+) imaging was used to study the effects fou2 on cytosolic Ca2+ concentrations.Six intragenic ouf suppressors with near wild-type (WT) JA pathway activity were recovered and one mutant, ouf8, affected the channel pore. At low luminal calcium concentrations, ouf8 had little detectable effect on fou2. However, increased vacuolar Ca2+ concentrations caused channel occlusion, selectively blocking K+ fluxes towards the cytoplasm. Cytosolic Ca2+ concentrations in unwounded fou2 were found to be lower than in the unwounded WT, but they increased in a similar manner in both genotypes following wounding.Basal JA pathway activity can be controlled solely by manipulating endomembrane cation flux capacities. We suggest that changes in endomembrane potential affect JA pathway activity.
http://onlinelibrary.wiley.com/doi/10.1111/nph.14754/abstract
5Plant Biotechnology JournalRust fungi are devastating plant pathogens and cause a large economic impact on wheat production worldwide. To overcome this rapidly loss of varieties resistance, we generated stable transgenic wheat plants expressing short interfering RNAs (siRNAs) targeting potentially vital genes of Puccinia striiformis f. sp. tritici(Pst). Protein kinase A (PKA) has been proved to play important roles in regulating the virulence of phytopathogenic fungi. PsCPK1, a PKA catalytic subunit gene from Pst, is highly induced at the early infection stage of Pst. The instantaneous silencing of PsCPK1 by barley stripe mosaic virus (BSMV)-mediated host-induced gene silencing (HIGS) results in a significant reduction in the length of infection hyphae and disease phenotype. These results indicate that PsCPK1 is an important pathogenicity factor by regulating Pst growth and development. Two transgenic lines expressing the RNA interference (RNAi) construct in a normally susceptible wheat cultivar displayed high levels of stable and consistent resistance to Pst throughout the T3 to T4 generations. The presence of the interfering RNAs in transgenic wheat plants was confirmed by northern blotting, and these RNAs were found to efficiently down-regulate PsCPK1 expression in wheat. The present study addresses important aspects for the development of fungal-derived resistance through the expression of silencing constructs in host plants as a powerful strategy to control cereal rust diseases.
http://onlinelibrary.wiley.com/doi/10.1111/pbi.12829/abstract
3-Hydroxy-3-methylglutaryl-coenzyme A synthase (HMGS) in the mevalonate (MVA) pathway generates isoprenoids including phytosterols. Dietary phytosterols are important because they can lower blood cholesterol levels. Previously, the overexpression of Brassica juncea wild-type (wt) and mutant (S359A) BjHMGS1 in Arabidopsis up-regulated several genes in sterol biosynthesis and increased sterol content. Recombinant S359A had earlier displayed a 10-fold higher in vitro enzyme activity. Furthermore, tobacco HMGS-overexpressors (OEs) exhibited improved sterol content, plant growth and seed yield. Increased growth and seed yield in tobacco OE-S359A over OE-wtBjHMGS1 coincided with elevations in NtSQSexpression and sterol content. Herein, the overexpression of wt and mutant (S359A) BjHMGS1 in a crop plant, tomato (Solanum lycopersicum), caused an accumulation of MVA-derived squalene and phytosterols, as well as methylerythritol phosphate (MEP)-derived α-tocopherol (vitamin E) and carotenoids, which are important to human health as antioxidants. In tomato HMGS-OE seedlings, genes associated with the biosyntheses of C10, C15 and C20 universal precursors of isoprenoids, phytosterols, brassinosteroids, dolichols, methylerythritol phosphate, carotenoid and vitamin E were up-regulated. In OE-S359A tomato fruits, increased squalene and phytosterol content over OE-wtBjHMGS1 was attributed to heightenedSlHMGR2, SlFPS1, SlSQS and SlCYP710A11 expression. In both tomato OE-wtBjHMGS1 and OE-S359A fruits, the up-regulation of SlGPS and SlGGPPS1 in the MEP pathway that led to α-tocopherol and carotenoid accumulation, indicated cross-talk between the MVA and MEP pathways. Taken together, the manipulation of BjHMGS1 represents a promising strategy to simultaneously elevate health-promoting squalene, phytosterols, α-tocopherol and carotenoids in tomato, an edible fruit.
http://onlinelibrary.wiley.com/doi/10.1111/pbi.12828/abstract
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