Genome-wide identification and characterization of polycomb repressive complex 2 core components in upland cotton (Gossypium hirsutum L.).

BACKGROUND: The evolutionarily conserved Polycomb Repressive Complex 2 (PRC2) plays a vital role in epigenetic gene repression by depositing tri-methylation on lysine residue K27 of histone H3 (H3K27me3) at the target loci, thus participating in diverse biological processes. However, few reports about PRC2 are available in plant species with large and complicated genomes, like cotton. RESULTS: Here, we performed a genome-wide identification and comprehensive analysis of cotton PRC2 core components, especially in upland cotton (Gossypium hirsutum). Firstly, a total of 8 and 16 PRC2 core components were identified in diploid and tetraploid cotton species, respectively. These components were classified into four groups, E(z), Su(z)12, ESC and p55, and the members in the same group displayed good collinearity, similar gene structure and domain organization. Next, we cloned G. hirsutum PRC2 (GhPRC2) core components, and found that most of GhPRC2 proteins were localized in the nucleus, and interacted with each other to form multi-subunit complexes. Moreover, we analyzed the expression profile of GhPRC2 genes. The transcriptome data and quantitative real-time PCR (qRT-PCR) assays indicated that GhPRC2 genes were ubiquitously but differentially expressed in various tissues, with high expression levels in reproductive organs like petals, stamens and pistils. And the expressions of several GhPRC2 genes, especially E(z) group genes, were responsive to various abiotic and biotic stresses, including drought, salinity, extreme temperature, and Verticillium dahliae (Vd) infection. CONCLUSION: We identified PRC2 core components in upland cotton, and systematically investigated their classifications, phylogenetic and synteny relationships, gene structures, domain organizations, subcellular localizations, protein interactions, tissue-specific and stresses-responsive expression patterns. Our results will provide insights into the evolution and composition of cotton PRC2, and lay the foundation for further investigation of their biological functions and regulatory mechanisms.

Strain Engineering of the NiTe/Ni2P Heterostructure to Boost the Oxygen Evolution Reaction.

Discovering highly efficient and stable non-precious metal catalysts for the oxygen evolution reaction (OER) is crucial for energy conversion in water splitting. However, preparing high-performance OER catalysts and elucidating the structural changes in the process are still challenging. Herein, we synthesize the NiTe/Ni2P heterostructure and demonstrate the strain engineering of NiTe/Ni2P via the lattice incompatibility between the phosphide and the telluride. The strain engineering of the NiTe/Ni2P heterostructure not only significantly boosts the OER activity but also effectively stabilizes the intrinsic structure of the catalyst after the OER process by using the in situ-produced metal salt as a protection layer. After the OER stability test, no oxyhydroxide phase is observed, and in situ Raman spectroscopy reveals that a voltage-dependent phase transition appears during the OER, which is different from most previously reported Ni-based catalysts, for which the generation of irreversible NiOOH occurs after the OER. Density functional theory calculations further reveal that the tensile strain of Ni2P will inhibit the presence of irreversible phase transitions of Ni2P into NiOOH due to the weak adsorption ability of the oxygen species caused by strain engineering. In short, this work opens a new gate for using strain nanotechnology to design high-performance OER catalysts.

SmCIP7, a COP1 interactive protein, positively regulates anthocyanin accumulation and fruit size in eggplant.

In higher plants, COP1 (Constitutively Photomorphogenic 1) acts as a central regulator of light-signaling networks and globally conditions the target proteins via the ubiquitin-proteasome pathway. However, the function of COP1-interacting proteins in light-regulated fruit coloration and development remains unknown in Solanaceous plants. Here, a COP1-interacting protein-encoding gene, SmCIP7, expressed specifically in the eggplant (Solanum melongena L.) fruit, was isolated. Gene-specific silencing of SmCIP7 using RNA interference (RNAi) significantly altered fruit coloration, fruit size, flesh browning, and seed yield. SmCIP7-RNAi fruits showed evident repression of the accumulation of anthocyanins and chlorophyll, indicating functional similarities between SmCIP7 and AtCIP7. However, the reduced fruit size and seed yield indicated SmCIP7 had evolved a distinctly new function. With the comprehensive application of HPLC-MS, RNA-seq, qRT-PCR, Y2H, BiFC, LCI, and dual-luciferase reporter system (DLR™), it was found that SmCIP7, a COP1 interactive protein in light signaling promoted anthocyanin accumulation, probably by regulating the transcription of SmTT8. Additionally, the drastic up-regulation of SmYABBY1, a homologous gene of SlFAS, might account for the strongly retarded fruit growth in SmCIP7-RNAi eggplant. Altogether, this study proved that SmCIP7 is an essential regulatory gene to modulate fruit coloration and development, serving as a key gene locus in eggplant molecular breeding.

Comparative Transcriptome Analysis of the Skin-Specific Accumulation of Anthocyanins in Black Peanut ( Arachis hypogaea L.).

As an oil crop with good taste and profuse nutrition, peanut ( Arachis hypogaea L.) is grown worldwide, mainly for edible seeds. Black peanuts attract more attention for their appealing color and health-promoting anthocyanins. Here, two cyanidin-based anthocyanins and four quercetin-based flavonols were separated and identified from skins of two black cultivars (Zi Yu and Zi Guan) by HPLC-ESI-Q-TOF-MS. To study the anthocyanin accumulation, libraries constructed from the mRNA of skins of Zi Yu and white cultivar (Bai Yu) were sequenced, and 4042 differentially expressed genes were identified. Gene ontology and KEGG pathway analysis underlined the importance of the high expression of flavonoid biosynthetic and regulatory genes in seed skin of Zi Yu. Furthermore, expression profiles of these genes were analyzed carefully in four representative peanut cultivars. Altogether, these results strongly indicate that the up-regulation of transcriptional activators (AhMYB1, AhMYB2, and AhTT8) accounts for the skin-specific accumulation of anthocyanins in black peanut.

Physiological and transcriptome analyses of Opisthopappus taihangensis in response to drought stress.

BACKGROUND: Water scarcity is considered to be a severe environmental constraint to plant survival and productivity. Studies on drought-tolerant plants would definitely promote a better understanding of the regulatory mechanism lying behind the adaptive response of plants to drought. Opisthopappus taihangensis (ling) shih is a typical drought-tolerant perennial plant species endemically distributed across the Taihang Mountains in China, but the underlying mechanism for drought tolerance of this particular species remains elusive. RESULTS: To mimic natural drought stress, O. taihangensis plants were treated with two different concentrations (25% and 5%) of polyethylene glycol (PEG6000), which represent the H group (high salinity) and the L group (low salinity), respectively. The physiological characteristics of these two groups of plants, including relative water content maintenance (RWC), proline content and chlorophyll content were assessed and compared with plants in the control group (CK), which had normal irrigation. There was not a significant difference in RWC when comparing plants in the L group with the control group. Proline was accumulated to a higher level, and chlorophyll content was decreased slightly in plants under low drought stress. In plants from the H group, a lower RWC was observed. Proline was accumulated to an even higher level when compared with plants from the L group, and chlorophyll content was further reduced in plants under high drought stress. Transcriptomic analysis was carried out to look for genes that are differentially expressed (DEGs) in O. taihangensis plants coping adaptively with the two levels of drought stress. A total of 23,056 genes are differentially expressed between CK and L, among which 12,180 genes are up-regulated and 10,876 genes are down-regulated. Between H and L, 6182 genes are up-regulated and 1850 genes are down-regulated, which gives a total of 8032 genes. The highest number of genes, that are differentially expressed, was obtained when a comparison was made between CK and H. A total of 43,074 genes were found to be differentially expressed with 26,977 genes up-regulated and 16,097 genes down-regulated. Further analysis of these genes suggests that many of the up-regulated genes are enriched in pathways involved in amino acid metabolism. Besides, 39 transcription factors (TFs) were found to be continuously up-regulated with the increase of drought stress level. CONCLUSION: Taken together, the results indicate that O. taihangensis plants are able to live adaptively under drought stress by responding physiologically and regulating the expression of a substantial number of drought-responsive genes and TFs to avoid adverse effects.