Eggplant NAC domain transcription factor SmNST1 as an activator promotes secondary cell wall thickening.

NAC-domain transcription factors (TFs) are plant-specific transcriptional regulators playing crucial roles in plant secondary cell wall (SCW) biosynthesis. SCW is important for plant growth and development, maintaining plant morphology, providing rigid support, ensuring material transportation and participating in plant stress responses as a protective barrier. However, the molecular mechanisms underlying SCW in eggplant have not been thoroughly explored. In this study, the NAC domain TFs SmNST1 and SmNST2 were cloned from the eggplant line 'Sanyue qie'. SmNST1 and SmNST2 expression levels were the highest in the roots and stems. Subcellular localization analysis showed that they were localized in the cell membrane and nucleus. Their overexpression in transgenic tobacco showed that SmNST1 promotes SCW thickening. The expression of a set of SCW biosynthetic genes for cellulose, xylan and lignin, which regulate SCW formation, was increased in transgenic tobacco. Bimolecular fluorescence and luciferase complementation assays showed that SmNST1 interacted with SmNST2 in vivo. Yeast one-hybrid, electrophoretic mobility shift assay (EMSA) and Dual-luciferase reporter assays showed that SmMYB26 directly bound to the SmNST1 promoter and acted as an activator. SmNST1 and SmNST2 interact with the SmMYB108 promoter and repress SmMYB108 expression. Altogether, we showed that SmNST1 positively regulates SCW formation, improving our understanding of SCW biosynthesis transcriptional regulation.

[The regulatory role of the RUS family in plant growth and development].

The chloroplast genome encodes many key proteins involved in photosynthesis and other metabolic processes, and metabolites synthesized in chloroplasts are essential for normal plant growth and development. Root-UVB (ultraviolet radiation B)-sensitive (RUS) family proteins composed of highly conserved DUF647 domain belong to chloroplast proteins. They play an important role in the regulation of various life activities such as plant morphogenesis, material transport and energy metabolism. This article summarizes the recent advances of the RUS family proteins in the growth and development of plants such as embryonic development, photomorphological construction, VB6 homeostasis, auxin transport and anther development, with the aim to facilitate further study of its molecular regulation mechanism in plant growth and development.

Comparative transcriptome analysis reveals the involvement of an MYB transcriptional activator, SmMYB108, in anther dehiscence in eggplant.

Male sterility is a highly attractive agronomic trait as it effectively prevents self-fertilization and facilitates the production of high-quality hybrid seeds in plants. Timely release of mature pollen following anther dehiscence is essential for stamen development in flowering plants. Although several theories have been proposed regarding this, the specific mechanism of anther development in eggplant remains elusive. In this study, we selected an R2R3-MYB transcription factor gene, SmMYB108, that encodes a protein localized primarily in the nucleus by comparing the transcriptomics of different floral bud developmental stages of the eggplant fertile line, F142. Quantitative reverse transcription polymerase chain reaction revealed that SmMYB108 was preferentially expressed in flowers, and its expression increased significantly on the day of flowering. Overexpression of SmMYB108 in tobacco caused anther dehiscence. In addition, we found that SmMYB108 primarily functions as a transcriptional activator via C-terminal activation (amino acid 262-317). Yeast one-hybrid and dual-luciferase reporter assays revealed that genes (SmMYB21, SmARF6, and SmARF8) related to anther development targeted the SmMYB108 promoter. Overall, our results provide insights into the molecular mechanisms involved in the regulation of anther development by SmMYB108.

The regulatory roles of MYC TFs in plant stamen development.

The stamen, as the male reproductive organ of flowering plants, plays a critical role in completing the life cycle of plants. MYC transcription factors are members of the bHLH IIIE subgroup and participate in a number of plant biological processes. In recent decades, a number of studies have confirmed that MYC transcription factors actively participate in the regulation of stamen development and have a critical impact on plant fertility. In this review, we summarized how MYC transcription factors play a role in regulating secondary thickening of the anther endothecium, the development and degradation of the tapetum, stomatal differentiation, and the dehydration of the anther epidermis. With regard to anther physiological metabolism, MYC transcription factors control dehydrin synthesis, ion and water transport, and carbohydrate metabolism to influence pollen viability. Additionally, MYCs participate in the JA signal transduction pathway, where they directly or indirectly control the development of stamens through the ET-JA, GA-JA, and ABA-JA pathways. By identifying the functions of MYCs during plant stamen development, it will help us to obtain a more comprehensive understanding not only on the molecular functions of this TF family but also the mechanisms underlying stamen development.

Transcriptomics reveals the molecular mechanisms of flesh colour differences in eggplant (Solanum melongena).

BACKGROUND: Fruit flesh colour is not only an important commodity attribute of eggplant but is also closely related to maturity. However, very little is known about its formation mechanism in eggplant. RESULTS: Two inbred lines of eggplant, green 'NC7' and white 'BL', were used in this study to explain the differences in flesh colour. Transcriptome sequencing results revealed a total of 3304 differentially expressed genes (DEGs) in NC7 vs. BL. Of the DEGs obtained, 2050 were higher and 1254 were lower in BL. These DEGs were annotated to 126 pathways, where porphyrin and chlorophyll metabolism, flavonoid biosynthesis, and photosynthesis-antenna proteins play vital roles in the colour formation of eggplant flesh. At the same time, Gene Ontology (GO) enrichment significance analysis showed that a large number of unigenes involved in the formation of chloroplast structure were lower in BL, which indicated that the formation of chloroplasts in white-fleshed eggplant was blocked. This was confirmed by transmission electron microscopy (TEM), which found only leucoplasts but no chloroplasts in the flesh cells of white-fleshed eggplant. Several genes encoding ERF and bHLH transcription factors were predicted to participate in the regulation of chlorophyll biosynthetic genes. CONCLUSIONS: The results of this study indicated that differences in the gene expression of the chlorophyll metabolic pathway were the main cause of the different flesh colour formations. These findings will increase our understanding of the genetic basis in eggplant flesh colors formation mechanism.

Electrically switchable van der Waals magnon valves.

Van der Waals magnets have emerged as a fertile ground for the exploration of highly tunable spin physics and spin-related technology. Two-dimensional (2D) magnons in van der Waals magnets are collective excitation of spins under strong confinement. Although considerable progress has been made in understanding 2D magnons, a crucial magnon device called the van der Waals magnon valve, in which the magnon signal can be completely and repeatedly turned on and off electrically, has yet to be realized. Here we demonstrate such magnon valves based on van der Waals antiferromagnetic insulator MnPS3. By applying DC electric current through the gate electrode, we show that the second harmonic thermal magnon (SHM) signal can be tuned from positive to negative. The guaranteed zero crossing during this tuning demonstrates a complete blocking of SHM transmission, arising from the nonlinear gate dependence of the non-equilibrium magnon density in the 2D spin channel. Using the switchable magnon valves we demonstrate a magnon-based inverter. These results illustrate the potential of van der Waals anti-ferromagnets for studying highly tunable spin-wave physics and for application in magnon-base circuitry in future information technology.

Screening and Interaction Analysis Identify Genes Related to Anther Dehiscence in Solanum melongena L.

Anther indehiscence is an important form of functional male sterility that can facilitate the production of hybrid seeds. However, the molecular mechanisms of anther indehiscence-based male sterility in eggplant (Solanum melongena L.) have not been thoroughly explored. We performed transcriptome sequencing and real-time quantitative reverse transcription-PCR (qRT-PCR) assays to compare the fertile line (F142) and male sterile line (S12) eggplant. We identified 2,670 differentially expressed genes (DEGs) between lines. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses identified 31 DEGs related to hormone biosynthesis. We, therefore, measured phytohormone contents, such as jasmonic acid (JA), auxin (IAA), gibberellin (GA), and abscisic acid (ABA) in S12 and F142. There were differences in IAA, GA3, and ABA levels between S12 and F142, while JA levels were significantly lower in S12 than in F142. Five key genes in the JA signaling pathway were differentially expressed in S12 vs. F142. Of these, SmJAZ1 and SmJAR1 were significantly upregulated and SmDAD1, SmLOX, and SmCOI1 were downregulated in S12 vs. F142. Protein-protein interaction studies identified a direct interaction between SmDAD1 and SmLOX, while SmDAD1 failed to interact with SmJAR1, SmCOI1, and SmJAZ1. The data represent a valuable resource for further exploration of regulatory mechanisms underlying anther dehiscence in eggplant.

Thermal expansion coefficient of few-layer MoS2 studied by temperature-dependent Raman spectroscopy.

The thermal expansion coefficient is an important thermal parameter that influences the performance of nanodevices based on two-dimensional materials. To obtain the thermal expansion coefficient of few-layer MoS2, suspended MoS2 and supported MoS2 were systematically investigated using Raman spectroscopy in the temperature range from 77 to 557 K. The temperature-dependent evolution of the Raman frequency shift for suspended MoS2 exhibited prominent differences from that for supported MoS2, obviously demonstrating the effect due to the thermal expansion coefficient mismatch between MoS2 and the substrate. The intrinsic thermal expansion coefficients of MoS2 with different numbers of layers were calculated. Interestingly, negative thermal expansion coefficients were obtained below 175 K, which was attributed to the bending vibrations in the MoS2 layer during cooling. Our results demonstrate that Raman spectroscopy is a feasible tool for investigating the thermal properties of few-layer MoS2 and will provide useful information for its further application in photoelectronic devices.

[Analysis of differential genes and metabolic pathway related to functional male sterility in eggplant].

Based on observing the cytological characteristics of the flower buds of the functional male sterile line (S13) and the fertile line (F142) in eggplant, it was found that the disintegration period of the annular cell clusters in S13 anther was 2 days later than that of F142, and the cells of stomiun tissue and tapetum in F142 disintegrated on the blooming day, while it did not happen in S13. The comparative transcriptomic analysis showed that there were 1 436 differential expression genes (DEGs) (651 up-regulated and 785 down-regulated) in anthers of F142 and S13 at 8, 5 days before flowering and flowering day. The significance analysis of GO enrichment indicated that there were more unigene clusters involved in single cell biological process, metabolism process and cell process, and more catalytic activity and binding function were involved in molecular functions. Through KEGG annotation we found that the common DEGs were mainly enriched in the biosynthesis of secondary metabolites, metabolic pathway, protein processing in endoplasmic reticulum, biosynthesis of amino acids, carbon metabolism and plant hormone signal transduction. The fifteen genes co-expression modules were identified from 16 465 selected genes by weighted gene co-expression network analysis (WGCNA), three of which (Plum2, Royalblue and Bisque4 modules) were highly related to S13 during flower development. KEGG enrichment showed that the specific modules could be enriched in phenylpropanoid biosynthesis, photosynthesis, porphyrin and chlorophyll metabolism, α-linolenic acid metabolism, polysaccharide biosynthesis and metabolism, fatty acid degradation and the mutual transformation of pentose and glucuronic acid. These genes might play important roles during flower development of S13. It provided a reference for further study on the mechanism of anther dehiscence in eggplant.

Comparative transcriptome analysis provides insight into the molecular mechanisms of anther dehiscence in eggplant (Solanum melongena L.).

Anther dehiscence releases pollen and therefore is a key event in plant sexual reproduction. Although anther dehiscence has been intensively studied in some plants, such as Arabidopsis thaliana and rice (Oryza sativa), the molecular mechanism of anther dehiscence in eggplant (Solanum melongena) is largely unknown. To provide insight into this mechanism, we used RNA-sequencing (RNA-seq) to analyze the transcriptomic profiles of one natural male-fertile line (F142) and two male-sterile lines (S12 and S13). We assembled 88,414 unigenes and identified 3446 differentially expressed genes (DEGs). GO and KEGG analysis indicated that these DEGs were mainly involved in "metabolic process", "catalytic activity", "biosynthesis of amino acids", and "carbon metabolism". The present study provides comprehensive transcriptomic profiles of eggplants that do and do not undergo anther dehiscence, and identifies a number of genes and pathways associated with anther dehiscence. The information deepens our understanding of the molecular mechanisms of anther dehiscence in eggplant.

Plasmonic Hybrids of MoS2 and 10-nm Nanogap Arrays for Photoluminescence Enhancement.

Monolayer MoS2 has attracted tremendous interest, in recent years, due to its novel physical properties and applications in optoelectronic and photonic devices. However, the nature of the atomic-thin thickness of monolayer MoS2 limits its optical absorption and emission, thereby hindering its optoelectronic applications. Hybridizing MoS2 by plasmonic nanostructures is a critical route to enhance its photoluminescence. In this work, the hybrid nanostructure has been proposed by transferring the monolayer MoS2 onto the surface of 10-nm-wide gold nanogap arrays fabricated using the shadow deposition method. By taking advantage of the localized surface plasmon resonance arising in the nanogaps, a photoluminescence enhancement of ~20-fold was achieved through adjusting the length of nanogaps. Our results demonstrate the feasibility of a giant photoluminescence enhancement for this hybrid of MoS2/10-nm nanogap arrays, promising its further applications in photodetectors, sensors, and emitters.

Author Correction: Universal mechanical exfoliation of large-area 2D crystals.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

SmCOI1 affects anther dehiscence in a male-sterile Solanum melongena line.

Anther indehiscence is an important form of functional male sterility that can facilitate the production of hybrid seed; however, the molecular mechanisms of anther indehiscence-based male sterility have not been thoroughly explored in eggplant (Solanum melongena L.). Here, we used two-dimensional gel electrophoresis to compare the protein profiles in the anthers of normally developing (F142) and anther indehiscent (S16) S. melongena plants. Four differentially expressed proteins were identified using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry. Of these proteins, the transcript accumulation of the eggplant CORONATINE INSENSITIVE1 (SmCOI1) was significantly downregulated in S16 relative to F142. Phylogenetic analysis showed that SmCOI1 has high amino acid sequence similarity and clustered into the same subgroup as its homologs in other members of the Solanaceae. Subcellular localization analysis showed that SmCOI1 localized to the nucleus. Moreover, reverse-transcription quantitative PCR revealed that the jasmonic acid pathway genes SmJAZ1 and SmOPR3 are upregulated in F142 relative to S16. Protein-protein interaction studies identified a direct interaction between SmCOI1 and SmOPR3, but SmCOI1 failed to interact with SmJAZ1. These findings shed light on the regulatory mechanisms of anther dehiscence in eggplant.

Universal mechanical exfoliation of large-area 2D crystals.

Two-dimensional materials provide extraordinary opportunities for exploring phenomena arising in atomically thin crystals. Beginning with the first isolation of graphene, mechanical exfoliation has been a key to provide high-quality two-dimensional materials, but despite improvements it is still limited in yield, lateral size and contamination. Here we introduce a contamination-free, one-step and universal Au-assisted mechanical exfoliation method and demonstrate its effectiveness by isolating 40 types of single-crystalline monolayers, including elemental two-dimensional crystals, metal-dichalcogenides, magnets and superconductors. Most of them are of millimeter-size and high-quality, as shown by transfer-free measurements of electron microscopy, photo spectroscopies and electrical transport. Large suspended two-dimensional crystals and heterojunctions were also prepared with high-yield. Enhanced adhesion between the crystals and the substrates enables such efficient exfoliation, for which we identify a gold-assisted exfoliation method that underpins a universal route for producing large-area monolayers and thus supports studies of fundamental properties and potential application of two-dimensional materials.

Overexpression of SlOFP20 affects floral organ and pollen development.

The OVATE gene was initially identified in tomato and serves as a key regulator of fruit shape. There are 31 OFP members in the tomato genome. However, their roles in tomato growth and reproductive development are largely unknown. Here, we cloned the OFP transcription factor SlOFP20. Tomato plants overexpressing SlOFP20 displayed several phenotypic defects, including an altered floral architecture and fruit shape and reduced male fertility. SlOFP20 overexpression altered the expression levels of some brassinosteroid (BR)-associated genes, implying that SlOFP20 may play a negative role in the BR response, similar to its ortholog OsOFP19 in rice. Moreover, the transcript accumulation of gibberellin (GA)-related genes was significantly affected in the transgenic lines. SlOFP20 may play an important role in the crosstalk between BR and GA. The pollen germination assay suggested that the pollen germination rate of SlOFP20-OE plants was distinctly lower than that of WT plants. In addition, the tomato pollen-associated genes SlCRK1, SlPMEI, LePRK3, SlPRALF, and LAT52 were all suppressed in the transgenic lines. Our data imply that SlOFP20 may affect floral organ and pollen development by modulating BR and GA signaling in tomato.

The eggplant transcription factor MYB44 enhances resistance to bacterial wilt by activating the expression of spermidine synthase.

Bacterial wilt (BW) caused by Ralstonia solanacearum is a serious disease affecting the production of Solanaceae species, including eggplant (Solanum melongena). However, few resistance genes have been identified in eggplant, and therefore the underlying mechanism of BW resistance remains unclear. Hence, we investigated a spermidine synthase (SPDS) gene from eggplant and created knock-down lines with virus-induced gene silencing. After eggplant was infected with R. solanacearum, the SmSPDS gene was induced, concurrent with increased spermidine (Spd) content, especially in the resistant line. We speculated that Spd plays a significant role in the defense response of eggplant to BW. Moreover, using the yeast one-hybrid approach and dual luciferase-based transactivation assay, an R2R3-MYB transcription factor, SmMYB44, was identified as directly binding to the SmSPDS promoter, activating its expression. Overexpression of SmMYB44 in eggplant induced the expression of SmSPDS and Spd content, increasing the resistance to BW. In contrast, the SmMYB44-RNAi transgenic plants showed more susceptibility to BW compared with the control plants. Our results provide insight into the SmMYB44-SmSPDS-Spd module involved in the regulation of resistance to R. solanacearum. This research also provides candidates to enhance resistance to BW in eggplant.

Genome-Wide Analysis of the MADS-Box Transcription Factor Family in Solanum lycopersicum.

MADS-box family genes encode transcription factors that are involved in multiple developmental processes in plants, especially in floral organ specification, fruit development, and ripening. However, a comprehensive analysis of tomato MADS-box family genes, which is an important model plant to study flower fruit development and ripening, remains obscure. To gain insight into the MADS-box genes in tomato, 131 tomato MADS-box genes were identified. These genes could be divided into five groups (Mα, Mß, Mγ, Mδ, and MIKC) and were found to be located on all 12 chromosomes. We further analyzed the phylogenetic relationships among Arabidopsis and tomato, as well as the protein motif structure and exon-intron organization, to better understand the tomato MADS-box gene family. Additionally, owing to the role of MADS-box genes in floral organ identification and fruit development, the constitutive expression patterns of MADS-box genes at different stages in tomato development were identified. We analyzed 15 tomato MADS-box genes involved in floral organ identification and five tomato MADS-box genes related to fruit development by qRT-PCR. Collectively, our study provides a comprehensive and systematic analysis of the tomato MADS-box genes and would be valuable for the further functional characterization of some important members of the MADS-box gene family.

A histone deacetylase gene, SlHDA3, acts as a negative regulator of fruit ripening and carotenoid accumulation.

KEY MESSAGE: SlHDA3 functions as an inhibitor and regulates tomato fruit ripening and carotenoid accumulation. Post-translational modifications, including histones acetylation, play a pivotal role in the changes of chromatin structure dynamic modulation and gene activity. The regulation of histone acetylation is achieved by the action of histone acetyltransferases and deacetylases, which play crucial roles in the regulation of transcription activation. There is an increasing research focus on histone deacetylation in crops, but the role of histone deacetylase genes (HDACs) in tomato has not been elucidated. With the aim of characterizing the tomato RPD3/HDA1 family histone deacetylase genes, SlHDA3 was isolated and its RNA interference (RNAi) lines was obtained. The fruit of SlHDA3 RNAi lines exhibited accelerated ripening process along with short shelf life characteristics. The accumulation of carotenoid was increased due to the alteration of the carotenoid pathway flux. Climacteric ethylene production also stimulated along with significantly up-regulated expression of ethylene biosynthetic genes (ACS2, ACS4, ACO1 and ACO3) and fruit ripening-associated genes (RIN, E4, E8, PG, Pti4, LOXB, Cnr and TAGL1) in SlHDA3 RNAi lines. Besides, fruit cell wall metabolism-associated genes (HEX, MAN, TBG4, XTH5 and XYL) were enhanced in transgenic lines. Relative to wild type (WT) plants, SlHDA3 RNAi seedlings displayed shorter hypocotyls and more sensitivity to ACC (1-aminocyclopropane-1-carboxylate). These results indicated that SlHDA3 is involved in the regulation of fruit ripening by affecting ethylene biosynthesis and carotenoid accumulation.

Silencing SlAGL6, a tomato AGAMOUS-LIKE6 lineage gene, generates fused sepal and green petal.

KEY MESSAGE: Silencing SlAGL6 in tomato leads to fused sepal and green petal by influencing the expression of A-, B-class genes. AGAMOUS-LIKE6 (AGL6) lineage is an important clade MADS-box transcription factor and plays essential roles in various developmental programs especially in flower meristem and floral organ development. Here, we isolated a tomato AGL6 lineage gene SlAGL6 and successfully obtained several RNA interference (RNAi) lines. Silencing SlAGL6 led to abnormal fused sepals and light green petals with smaller size. The total chlorophyll content in transgenic petals increased and the morphology of epidermis cells altered. Further analysis showed that A-class gene MACROCALYX (MC) participating in sepal development and a NAC-domain gene GOBLET involving in boundary establishment were down-regulated in transgenic lines. In transgenic petals, two chlorophyll synthesis genes, Golden2-like1 (SlGLK1) and Golden2-like2 (SlGLK2), two photosystem-related genes, ribulose bisphosphate carboxylase small chain 3B (SlrbcS3B) and chlorophyll a/b-binding protein 7 (SlCab-7) were induced and three B-class genes TM6, TAP3 and SlGLO1 were repressed. These results suggest that SlAGL6 involves in tomato sepal and petal development.

Anthocyanin Accumulation and Molecular Analysis of Correlated Genes in Purple Kohlrabi (Brassica oleracea var. gongylodes L.).

Kohlrabi (Brassica oleracea var. gongylodes L.) is an important dietary vegetable cultivated and consumed widely for the round swollen stem. Purple kohlrabi shows abundant anthocyanin accumulation in the leaf and swollen stem. Here, different kinds of anthocyanins were separated and identified from the purple kohlrabi cultivar (Kolibri) by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry. In order to study the molecular mechanism of anthocyanin biosynthesis in purple kohlrabi, the expression of anthocyanin biosynthetic genes and regulatory genes in purple kohlrabi and a green cultivar (Winner) was examined by quantitative PCR. In comparison with the colorless parts in the two cultivars, most of the anthocyanin biosynthetic genes and two transcription factors were drastically upregulated in the purple tissues. To study the effects of light shed on the anthocyanin accumulation of kohlrabi, total anthocyanin contents and transcripts of associated genes were analyzed in sprouts of both cultivars grown under light and dark conditions.