The microRNA408-plantacyanin module balances plant growth and drought resistance by regulating reactive oxygen species homeostasis in guard cells.

The conserved microRNA (miRNA) miR408 enhances photosynthesis and compromises stress tolerance in multiple plants, but the cellular mechanism underlying its function remains largely unclear. Here, we show that in Arabidopsis (Arabidopsis thaliana), the transcript encoding the blue copper protein PLANTACYANIN (PCY) is the primary target for miR408 in vegetative tissues. PCY is preferentially expressed in the guard cells, and PCY is associated with the endomembrane surrounding individual chloroplasts. We found that the MIR408 promoter is suppressed by multiple abscisic acid (ABA)-responsive transcription factors, thus allowing PCY to accumulate under stress conditions. Genetic analysis revealed that PCY elevates reactive oxygen species (ROS) levels in the guard cells, promotes stomatal closure, reduces photosynthetic gas exchange, and enhances drought resistance. Moreover, the miR408-PCY module is sufficient to rescue the growth and drought tolerance phenotypes caused by gain- and loss-of-function of MYB44, an established positive regulator of ABA responses, indicating that the miR408-PCY module relays ABA signaling for regulating ROS homeostasis and drought resistance. These results demonstrate that miR408 regulates stomatal movement to balance growth and drought resistance, providing a mechanistic understanding of why miR408 is selected during land plant evolution and insights into the long-pursued quest of breeding drought-tolerant and high-yielding crops.

Increased long-distance and homo-trans interactions related to H3K27me3 in Arabidopsis hybrids.

In plants, the genome structure of hybrids changes compared with their parents, but the effects of these changes in hybrids remain elusive. Comparing reciprocal crosses between Col × C24 and C24 × Col in Arabidopsis using high-throughput chromosome conformation capture assay (Hi-C) analysis, we found that hybrid three-dimensional (3D) chromatin organization had more long-distance interactions relative to parents, and this was mainly located in promoter regions and enriched in genes with heterosis-related pathways. The interactions between euchromatin and heterochromatin were increased, and the compartment strength decreased in hybrids. In compartment domain (CD) boundaries, the distal interactions were more in hybrids than their parents. In the hybrids of CURLY LEAF (clf) mutants clfCol × clfC24 and clfC24 × clfCol , the heterosis phenotype was damaged, and the long-distance interactions in hybrids were fewer than in their parents with lower H3K27me3. ChIP-seq data revealed higher levels of H3K27me3 in the region adjacent to the CD boundary and the same interactional homo-trans sites in the wild-type (WT) hybrids, which may have led to more long-distance interactions. In addition, the differentially expressed genes (DEGs) located in the boundaries of CDs and loop regions changed obviously in WT, and the functional enrichment for DEGs was different between WT and clf in the long-distance interactions and loop regions. Our findings may therefore propose a new epigenetic explanation of heterosis in the Arabidopsis hybrids and provide new insights into crop breeding and yield increase.

Evaluation of genetic integrity of pearl millet seeds during aging by genomic-SSR markers.

Seed is an important way to store germplasm resources but its genetic integrity will decrease during long-term preservation. So, it's essential to update seeds according to the aging level of different species. Pearl millet [Cenchrus americanus (L.) Morrone syn., Pennisetum glaucum (L.) R. Br.] is a crucial forage grass, biofuel plant and important crops in the world bringing huge economic and ecological benefits. However, there is no report about the impact of aging on genetic integrity of its seeds. In this study, four genetic diversity indexes (the percentage of polymorphic bands, PPB; the effective number of alleles, Ne; the Nei's gene diversity index, H; the Shannon's information index, I) and 20 pairs of genomic-SSR primers were used to certify the optimal sample volume of pearl millet for molecular study and found that the best sample volume was 60. After the artificial aging test, the germination rate and four genetic diversity parameters (the number of alleles, Na; Ne; H; I) were used to evaluate the change of genetic integrity at different aging levels. The results showed that the germination rate and these four genetic diversity parameters declined with the increase of aging levels. Furthermore, when the germination rate of pearl millet seeds went down to 68.23%, a significant difference in genetic integrity was observed with unaged seeds. In conclusion, the optimal sample size of pearl millet was 60 and the critical point of germination rate to renew germplasm resources was 68.23% and these finds might contribute to the scientific study and the safe conservation of pearl millet.

Single-nucleus RNA and ATAC sequencing analyses provide molecular insights into early pod development of peanut fruit.

Peanut (Arachis hypogaea L.) is an important leguminous oil and economic crop that produces flowers aboveground and fruits belowground. Subterranean fruit-pod development, which significantly affects peanut production, involves complex molecular mechanisms that likely require the coordinated regulation of multiple genes in different tissues. To investigate the molecular mechanisms that underlie peanut fruit-pod development, we characterized the anatomical features of early fruit-pod development and integrated single-nucleus RNA-sequencing (snRNA-seq) and single-nucleus assay for transposase-accessible chromatin with sequencing (snATAC-seq) data at the single-cell level. We identified distinct cell types, such as meristem, embryo, vascular tissue, cuticular layer, and stele cells within the shell wall. These specific cell types were used to examine potential molecular changes unique to each cell type during pivotal stages of fruit-pod development. snRNA-seq analyses of differentially expressed genes revealed cell-type-specific insights that were not previously obtainable from transcriptome analyses of bulk RNA. For instance, we identified MADS-box genes that contributes to the formation of parenchyma cells and gravity-related genes that are present in the vascular cells, indicating an essential role for the vascular cells in peg gravitropism. Overall, our single-nucleus analysis provides comprehensive and novel information on specific cell types, gene expression, and chromatin accessibility during the early stages of fruit-pod development. This information will enhance our understanding of the mechanisms that underlie fruit-pod development in peanut and contribute to efforts aimed at improving peanut production.

Genetic and epigenetic signatures for improved breeding of cultivated blueberry.

Blueberry belongs to the Vaccinium genus and is a highly popular fruit crop with significant economic importance. It was not until the early twentieth century that they began to be domesticated through extensive interspecific hybridization. Here, we collected 220 Vaccinium accessions from various geographical locations, including 154 from the United States, 14 from China, eight from Australia, and 29 from Europe and other countries, comprising 164 Vaccinium corymbosum, 15 Vaccinium ashei, 10 lowbush blueberries, seven half-high blueberries, and others. We present the whole-genome variation map of 220 accessions and reconstructed the hundred-year molecular history of interspecific hybridization of blueberry. We focused on the two major blueberry subgroups, the northern highbush blueberry (NHB) and southern highbush blueberry (SHB) and identified candidate genes that contribute to their distinct traits in climate adaptability and fruit quality. Our analysis unveiled the role of gene introgression from Vaccinium darrowii and V. ashei into SHB in driving the differentiation between SHB and NHB, potentially facilitating SHB's adaptation to subtropical environments. Assisted by genome-wide association studies, our analysis suggested VcTBL44 as a pivotal gene regulator governing fruit firmness in SHB. Additionally, we conducted whole-genome bisulfite sequencing on nine NHB and 12 SHB cultivars, and characterized regions that are differentially methylated between the two subgroups. In particular, we discovered that the ß-alanine metabolic pathway genes were enriched for DNA methylation changes. Our study provides high-quality genetic and epigenetic variation maps for blueberry, which offer valuable insights and resources for future blueberry breeding.

Exogenous Methyl Jasmonate Improves Heat Tolerance of Perennial Ryegrass Through Alteration of Osmotic Adjustment, Antioxidant Defense, and Expression of Jasmonic Acid-Responsive Genes.

Perennial ryegrass (Lolium perenne L.) is an important cool-season grass species that is widely cultivated in temperate regions worldwide but usually sensitive to heat stress. Jasmonates (JAs) may have a positive effect on plant tolerance under heat stress. In this study, results showed that exogenous methyl jasmonic acid (MeJA) could significantly improve heat tolerance of perennial ryegrass through alteration of osmotic adjustment, antioxidant defense, and the expression of JA-responsive genes. MeJA-induced heat tolerance was involved in the maintenance of better relative water content (RWC), the decline of chlorophyll (Chl) loss for photosynthetic maintenance, as well as maintained lower electrolyte leakage (EL) and malondialdehyde (MDA) content under heat condition, so as to avoid further damage to plants. Besides, results also indicated that exogenous MeJA treatment could increase the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), thus enhancing the scavenging ability of reactive oxygen species, alleviating the oxidative damage caused by heat stress. Heat stress and exogenous MeJA upregulated transcript levels of related genes (LpLOX2, LpAOC, LpOPR3, and LpJMT) in JA biosynthetic pathway, which also could enhance the accumulation of JA and MeJA content. Furthermore, some NAC transcription factors and heat shock proteins may play a positive role in enhancing resistance of perennial ryegrass with heat stress.

Mn-Fe3O4 nanoparticles anchored on the urushiol functionalized 3D-graphene for the electrochemical detection of 4-nitrophenol.

Preparation of highly active and cost-effective electrode materials is of great interest in electrochemical detection. In this study, a simple urushiol-templated solvothermal method combined with calcination was proposed to fabricate N-doped three-dimensional graphene (3D-G) with Mn-doped Fe3O4 nanoparticles loaded on the surface (Mn-Fe3O4/3D-G). Because of the large active surface area, porous channel and high loading ratio of Mn-Fe3O4 nanoparticles, as-prepared Mn-Fe3O4/3D-G sensor showed high activity on the determination of 4-nitrophenol (4-NP), which are much improved from the control un-modified samples. The wide linear concentration range (5-100 µM), low detection limit (19 nM) and satisfactory recovery of 4-NP in various water samples (98.38-100.41%) indicated that the Mn-Fe3O4/3D-G electrode can be potentially used for real-world applications. This study gives a simple but meaningful strategy for constructing transition metal oxide/graphene composite materials with high electrocatalytic activity.

Facile preparation of composite flame retardantbased on conjugated microporous polymer hollow spheres.

The development of functional materials with better flame-retardant and thermal insulation properties has attracted considerable attention for energy storage applications in modern society. Here, we describe a facile approach for the preparation of conjugated microporous polymer hollow spheres (CMP-HSs) by using SiO2 nanoparticles as a template via the Sonogashira-Hagihara cross-coupling reaction. The as-synthesized CMP-HSs have good thermal stability with a thermal decomposition temperature of up to 281 °C, high porosity (the BET specific surface area is measured to be approximately 666 m2 g-1) along with lipophilic and hydrophobic characteristics. To further improve their flame retardancy, CMP-HSs were treated with dimethyl phosphonate (DMMP) though an immersion method to prepare the CMP-HSs composite (CMP-HSs-DMMP) flame-retardants. By introducing CMP-HSs-DMMP into the epoxy resin (EP) matrix, the as-prepared EP composites showed excellent flame-retardant properties, e.g., the peak heat release rate (pHRR) and total heat release (THR) value of EP composites containing only 0.2% CMP-HSs-DMMP flame-retardant were 650.9 kW m-2 and 79.4 MJ m-2 respectively, in the range of 0 °C - 650 °C, which are 19.6 ± 2% and 19.1 ± 5% lower than that of pure EP within the same temperature range. Considering the significant enhancement of its flame retardancy with only a slight dosage of CMP-HSs-DMMP, such CMP hollow sphere-based flame-retardant composites may have great potential as functional bulk materials or coatings in a variety of fireproofing applications.