The acyl-acyl carrier protein thioesterases GmFATA1 and GmFATA2 are essential for fatty acid accumulation and growth in soybean.

Acyl-acyl carrier protein (ACP) thioesterases (FAT) hydrolyze acyl-ACP complexes to release FA in plastids, which ultimately affects FA biosynthesis and profiles. Soybean GmFATA1 and GmFATA2 are homoeologous genes encoding oleoyl-ACP thioesterases whose role in seed oil accumulation and plant growth has not been defined. Using CRISPR/Cas9 gene editing mutation of Gmfata1 or 2 led to reduced leaf FA content and growth defect at the early seedling stage. In contrast, no homozygous double mutants were obtained. Combined this indicates that GmFATA1 and GmFATA2 display overlapping, but not complete functional redundancy. Combined transcriptomic and lipidomic analysis revealed a large number of genes involved in FA synthesis and FA chain elongation are expressed at reduced level in the Gmfata1 mutant, accompanied by a lower triacylglycerol abundance at the early seedling stage. Further analysis showed that the Gmfata1 or 2 mutants had increased composition of the beneficial FA, oleic acid. The growth defect of Gmfata1 could be at least partially attributed to reduced acetyl-CoA carboxylase activity, reduced abundance of five unsaturated monogalactosyldiacylglycerol lipids, and altered chloroplast morphology. On the other hand, overexpression of GmFATA in soybean led to significant increases in leaf FA content by 5.7%, vegetative growth, and seed yield by 26.9%, and seed FA content by 23.2%. Thus, overexpression of GmFATA is an effective strategy to enhance soybean oil content and yield.

Phosphate-dependent regulation of vacuolar trafficking of OsSPX-MFSs is critical for maintaining intracellular phosphate homeostasis in rice.

Vacuolar storage of inorganic phosphate (Pi) is essential for Pi homeostasis in plants. The SPX-MFS family proteins have been demonstrated to be vacuolar Pi transporters in many plant species. Transcriptional regulation of the predominant transporter among rice SPX-MFSs, OsSPX-MFS3, was only moderately suppressed by Pi starvation. Thus, post-transcriptional mechanisms were hypothesized to regulate the activity of OsSPX-MFS3. In this study, we found that the tonoplast localization of OsSPX-MFSs is inhibited under Pi-depleted conditions, resulting in their retention in the pre-vacuolar compartments (PVCs). A yeast two-hybrid screen identified that two SNARE proteins, OsSYP21 and OsSYP22, interact with the MFS domain of OsSPX-MFS3. Further genetic and cytological analyses indicate that OsSYP21 and OsSYP22 facilitate trafficking of OsSPX-MFS3 from PVCs to the tonoplast. Although a homozygous frameshift mutation in OsSYP22 appeared to be lethal, tonoplast localization of OsSPX-MFS3 was significantly inhibited in transgenic plants expressing a negative-dominant form of OsSYP22 (OsSYP22-ND), resulting in reduced vacuolar Pi concentrations in OsSYP22-ND plants. Under Pi-depleted conditions, the interaction between OsSYP22 and OsSPX-MFS3 was disrupted, and this process depended on the presence of the SPX domain. Deleting the SPX domains of OsSPX-MFSs resulted in their tonoplast localization under both Pi-depleted and Pi-replete conditions. Complementation of the osspx-mfs1/2/3 triple mutants with the MFS domain or the SPX domain of OsSPX-MFS3 confirmed that the MFS and SPX domains are responsive to Pi transport activity and Pi-dependent regulation, respectively. These data indicated that the SPX domains of OsSPX-MFSs sense cellular Pi (InsP) levels and, under Pi-depleted conditions, inhibit the interaction between OsSPX-MFSs and OsSYP21/22 and subsequent trafficking of OsSPX-MFSs from PVCs to the tonoplast.

Functional characterization of the three Oryza sativa SPX-MFS proteins in maintaining phosphate homoeostasis.

Plant vacuoles serve as the primary intracellular compartments for phosphorus (P) storage. The Oryza sativa genome contains three genes that encode SPX ( SYG1/ PHO81/ XPR1)-MFS ( Major Facility Superfamily) proteins (OsSPX-MFS1-3). The physiological roles of the three transporters under varying P conditions in laboratory and field are not known. To address this knowledge gap, we generated single, double and triple mutants for three OsSPX-MFS genes. All the mutants except Osspx-mfs2 display lower vacuolar Pi concentrations and OsSPX-MFSs overexpression plant display higher Pi accumulation, demonstrating that all OsSPX-MFSs are vacuolar Pi influx transporters. OsSPX-MFS3 plays the dominant role based on the phenotypes of single mutants in terms of growth, vacuolar and tissue Pi concentrations. OsSPX-MFS2 is the weakest and only functions as vacuole Pi sequestration in an Osspx-mfs1/3 background. The vacuolar Pi sequestration capacity was severely impaired in Osspx-mfs1/3 and Osspx-mfs1/2/3, which resulted in increased Pi allocation to aerial organs. High P in the panicle impaired panicle and fertility in Osspx-mfs1/3 and Osspx-mfs1/2/3. Osspx-mfs2 resulted in a more stable yield compared to the wild type under low P in field grown plants. The results suggest that alteration of vacuolar Pi sequestration may be a novel effective strategy to improve rice tolerance to low phosphorus in cropping systems.

DNA methylation is involved in acclimation to iron-deficiency in rice (Oryza sativa).

Iron (Fe) is an essential micronutrient in plants, and Fe limitation significantly affects plant growth, yield and food quality. While many studies have reported the transcriptomic profile and pursue molecular mechanism in response to Fe limitation, little is known if epigenetic factors play a role in response to Fe-deficiency. In this study, whole-genome bisulfite sequencing analysis, high-throughput RNA-Seq of mRNA, small RNA and transposable element (TE) expression with root and shoot organs of rice seedlings under Fe-sufficient and Fe-deficient conditions were performed. The results showed that widespread hypermethylation, especially for the CHH context, occurred after Fe-deficiency. Integrative analysis of methylation and transcriptome revealed that the transcript abundance of Fe-deficiency-induced genes was negatively correlated with nearby TEs and positively with the 24-nucleotide siRNAs. The ability of methylation to affect the physiology and molecular response to Fe-deficiency was tested using an exogenous DNA methyltransferase inhibitor (5-azacytidine), and genetically using a mutant for domains rearranged methyltransferase 2 (DRM2), that lacks CHH methylation. Both approaches resulted in decreased growth and Fe content in rice plants. Thus, alterations in specific methylation patterns, directed by siRNAs, play an important role in acclimation of rice to Fe-deficient conditions. Furthermore, comparison with other reports suggests this may be a universal mechanism to acclimate to limited nutrient availability.

Crystal structure and magnetic properties of the magnetically isolated zigzag chain in KGaCu(PO4)2.

Magnetism of any material depends on its crystal structure. However, two isostructural compounds such as MCuMoO4(OH) (M = Na, K) can have markedly different magnetic properties. Herein, we introduce a new method to describe the linkages between the O-atoms and their bridged Cu2+ ions in order to clearly illustrate the structure-magnetic property relationships. This new method can account for magnetic differences between the two isostructural MCuMoO4(OH) and is further confirmed by the rational design and development of a new compound KGaCu(PO4)2 with different linkages. The title compound crystalized in a space group of P21/c adopts a one-dimensional (1D) magnetically isolated S = 1/2 zigzag chain composed of elongated [CuO6] octahedra via sharing alternately equatorial and skew edges. O atoms at the skew edges bridge the equatorial and axial orbitals of neighbouring Cu2+ ions (denoted EOA), while those at the equatorial edges bridge the equatorial orbitals of Cu2+ ions (EOE). The nearest-neighbour (NN) magnetic coupling of Cu2+ ions with the EOA linkage at 2.821 Å in the title compound is negligible, whereas the NN magnetic coupling of Cu2+ ions with the EOE linkage at 2.974 Å is essential. Therefore, the zigzag chain containing alternating spin-exchange dimers and no-spin-exchange ones is similar in electronic configuration to the dimerization of the quasi-one-dimensional antiferromagnet. Magnetic investigation of analogous compounds with a 'trans-cis-trans-cis' configuration observed in the title compound may shed light on structural evolutions associated with spin-Peierls (SP) transition.

Transcriptomic Profiling of Fe-Responsive lncRNAs and Their Regulatory Mechanism in Rice.

Iron (Fe) deficiency directly affects crop growth and development, ultimately resulting in reduced crop yield and quality. Recently, long non-coding RNAs (lncRNAs) have been demonstrated to play critical regulatory roles in a multitude of pathways across numerous species. However, systematic screening of lncRNAs responding to Fe deficiency and their regulatory mechanism in plants has not been reported. In this work, 171 differently expressed lncRNAs (DE-lncRNAs) were identified based on analysis of strand-specific RNA-seq data from rice shoots and roots under Fe-deficient conditions. We also found several lncRNAs, which could generate miRNAs or act as endogenous target mimics to regulate expression of Fe-related genes. Analysis of interaction networks and gene ontology enrichment revealed that a number of DE-lncRNAs were associated with iron transport and photosynthesis, indicating a possible role of lncRNAs in regulation of Fe homeostasis. Moreover, we identified 76 potential lncRNA targets of OsbHLH156, a key regulator for transcriptional response to Fe deficiency. This study provides insight into the potential functions and regulatory mechanism of Fe-responsive lncRNAs and would be an initial and reference for any further studies regarding lncRNAs involved in Fe deficiency in plants.

Green leaf volatile (Z)-3-hexeny-1-yl acetate reduces salt stress in peanut by affecting photosynthesis and cellular redox homeostasis.

Green leaf volatiles (GLVs) are released by plants when they encounter biotic stress, but their functions in the response to abiotic stress have not been determined. We have previously shown that exogenous application of (Z)-3-hexeny-1-yl acetate (Z-3-HAC), a kind of GLV, could alleviate salt stress in peanut (Arachis hypogaea L.) seedlings; however, notably little is known concerning the transcription regulation mechanisms of Z-3-HAC. In this study, we comprehensively characterized the transcriptomes and physiological indices of peanut seedlings exposed to Z-3-HAC and/or salt stress. Analysis of transcriptome data showed that 1420 genes were upregulated in the seedlings primed with Z-3-HAC under salt stress compared with the non-primed treatment. Interestingly, these genes were significantly enriched in the photosynthetic and ascorbate metabolism-related categories, as well as several plant hormone metabolism pathways. The physiological data revealed that Z-3-HAC significantly increased the net photosynthetic rate, SPAD value, plant height and shoot biomass compared with the non-primed peanut seedlings under salt stress. A significantly higher ratio of K+ :Na+ , reduced-to-oxidized glutathione (GSH:GSSG), and ascorbate-to-dehydroascorbate (AsA:DHA) were also observed for the plants primed with Z-3-HAC compared with the salt stress control. Meanwhile, Z-3-HAC significantly increased the activity of enzymes in the AsA-GSH cycle. Taken together, these results highlight the importance of Z-3-HAC in protecting peanut seedlings against salt stress by affecting photosynthesis, cellular redox homeostasis, K+ :Na+ homeostasis, and phytohormones.

Priming With the Green Leaf Volatile (Z)-3-Hexeny-1-yl Acetate Enhances Salinity Stress Tolerance in Peanut (Arachis hypogaea L.) Seedlings.

Green leaf volatiles play vital roles in plant biotic stress; however, their functions in plant responses to abiotic stress have not been determined. The aim of this study was to investigate the possible role of (Z)-3-hexeny-1-yl acetate (Z-3-HAC), a kind of green leaf volatile, in alleviating the salinity stress of peanut (Arachis hypogaea L.) seedlings and the underlying physiological mechanisms governing this effect. One salt-sensitive and one salt-tolerant peanut genotype were primed with 200 µM Z-3-HAC at the 4-week-old stage before they were exposed to salinity stress. Physiological measurements showed that the primed seedlings possessed higher relative water content, net photosynthetic rate, maximal photochemical efficiency of photosystem II, activities of the antioxidant enzymes, and osmolyte accumulation under salinity conditions. Furthermore, the reactive oxygen species, electrolyte leakage, and malondialdehyde content in the third fully expanded leaves were significantly lower than in nonprimed plants. Additionally, we found that application of Z-3-HAC increased the total length, surface area, and volume of the peanut roots under salinity stress. These results indicated that the green leaf volatile Z-3-HAC protects peanut seedlings against damage from salinity stress through priming for modifications of photosynthetic apparatus, antioxidant systems, osmoregulation, and root morphology.

The Soybean Sugar Transporter GmSWEET15 Mediates Sucrose Export from Endosperm to Early Embryo.

Soybean (Glycine max) seed is primarily composed of a mature embryo that provides a major source of protein and oil for humans and other animals. Early in development, the tiny embryos grow rapidly and acquire large quantities of sugars from the liquid endosperm of developing seeds. An insufficient supply of nutrients from the endosperm to the embryo results in severe seed abortion and yield reduction. Hence, an understanding of the molecular basis and regulation of assimilate partitioning involved in early embryo development is important for improving soybean seed yield and quality. Here, we used expression profiling analysis to show that two paralogous sugar transporter genes from the SWEET (Sugars Will Eventually be Exported Transporter) family, GmSWEET15a and GmSWEET15b, were highly expressed in developing soybean seeds. In situ hybridization and quantitative real-time PCR showed that both genes were mainly expressed in the endosperm at the cotyledon stage. GmSWEET15b showed both efflux and influx activities for sucrose in Xenopus oocytes. In Arabidopsis (Arabidopsis thaliana), knockout of three AtSWEET alleles is required to see a defective, but not lethal, embryo phenotype, whereas knockout of both GmSWEET15 genes in soybean caused retarded embryo development and endosperm persistence, resulting in severe seed abortion. In addition, the embryo sugar content of the soybean knockout mutants was greatly reduced. These results demonstrate that the plasma membrane sugar transporter, GmSWEET15, is essential for embryo development in soybean by mediating Suc export from the endosperm to the embryo early in seed development.