Antibiofilm Mechanisms of the Helical G3 Peptide against Staphylococcus epidermidis.

Antibacterial peptides (ABPs) have been recognized as promising alternatives to conventional antibiotics due to their broad antibacterial spectrum, high antibacterial activity, and low possibility of inducing bacterial resistance. However, their antibiofilm mechanisms have not yet reached a consensus. In this study, we investigated the antibiofilm activity of a short helical peptide G3 against Staphylococcus epidermidis, one of the most important strains of medical device contamination. Studies show that G3 inhibits S. epidermidis biofilm formation in a variety of ways. In the initial adhesion stage, G3 changes the properties of bacterial surfaces, such as charges, hydrophobicity, and permeability, by rapidly binding to them, thus interfering with their initial adhesion. In the mature stage, G3 prefers to target extracellular polysaccharides, leading to the death of outside bacteria and the disruption of the three-dimensional (3D) architecture of the bacterial biofilm. Such efficient antibiofilm activity of G3 endows it with great potential in the treatment of infections induced by the S. epidermidis biofilm.

Enzymatic functionalization of decellularized tilapia skin scaffolds with enhanced skin regeneration.

The decellularized tilapia skin (dTS) has gained significant attention as a promising material for tissue regeneration due to its ability to provide unique structural and functional components that support cell growth, adhesion, and proliferation. However, the clinical application of dTS is limited by its low mechanical strength and rapid biodegradability. Herein, we prepare a novel RGD (arginine-glycine-aspartic acid) functionalized dTS scaffold (dTS/RGD) by using transglutaminase (TGase) crosslinking. The developed dTS/RGD scaffold possesses excellent properties, including a medium porosity of ∼59.2%, a suitable degradation rate of approximately 80% over a period of two weeks, and appropriate mechanical strength with a maximum tensile stress of ∼46.36 MPa which is much higher than that of dTS (∼32.23 MPa). These properties make the dTS/RGD scaffold ideal for promoting cell adhesion and proliferation, thereby accelerating skin wound healing in a full-thickness skin defect model. Such an enzymatic cross-linking strategy provides a favorable microenvironment for wound healing and holds great potential for application in skin regeneration engineering.

Arabidopsis FHY3 and FAR1 Regulate the Balance between Growth and Defense Responses under Shade Conditions.

Increasing crop yield per unit of area can be achieved by increasing planting density. However, high-density planting could trigger shade avoidance responses, which cause exaggerated growth and increased susceptibility to various diseases. Previous studies have shown that the rapid elongation of plants under shade (i.e., reduced red to far-red ratios) is regulated by phytochromes and various phytohormones. However, the detailed molecular mechanisms governing the interaction among these signaling pathways are not well understood. Here, we report that loss-of-function mutants of FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and FAR-RED-IMPAIRED RESPONSE1 (FAR1), which encode two homologous transcription factors essential for phytochrome signaling, exhibit an exaggerated shade avoidance phenotype. We show that FHY3 and FAR1 repress plant growth through directly activating the expression of two atypical basic helix-loop-helix transcriptional cofactors, PHYTOCHROME RAPIDLY REGULATED1 (PAR1) and PAR2, and that this process is antagonized by a group of JASMONATE ZIM-DOMAIN proteins, key repressors of the jasmonic acid (JA) signaling pathway, through physical interactions. Furthermore, we show that FHY3 interacts with MYC2, a key transcriptional regulator of JA responses, coordinately regulating JA-responsive defense gene expression. Our results unveil a previously unrecognized mechanism whereby plants balance their growth and defense responses through convergence of the phytochrome signaling pathway and JA signaling pathway under shade conditions.

Ordered Packing of ß-Sheet Nanofibrils into Nanotubes: Multi-hierarchical Assembly of Designed Short Peptides.

Although it is well-known proteins and their complexes are hierarchically organized and highly ordered structures, it remains a major challenge to replicate their hierarchical self-assembly process and to fabricate multihierarchical architectures with well-defined shapes and monodisperse characteristic sizes via peptide self-assembly. Here we describe an amphiphilic short peptide Ac-I3GGHK-NH2 that first preassembles into thin, left-handed ß-sheet nanofibrils, followed by their ordered packing into right-handed nanotubes. The key intermediate morphology and structures featuring the hierarchical process are simultaneously demonstrated. Further mechanistic exploration with the variants Ac-I3GGGK-NH2, Ac-I3GGFK-NH2, and Ac-I3GGDHDK-NH2 reveals the vital role of multiple His-His side chain interactions between nanofibrils in mediating higher-order assembly and architectures. Altogether, our findings not only advance current understanding of hierarchical assembly of peptides and proteins but also afford a paradigm of how to take advantage of side chain interactions to construct higher-order assemblies with enhanced complexities.

Mutation analysis of TCOF1 gene in Chinese Treacher Collins syndrome patients.

BACKGROUND: Treacher Collins syndrome (TCS) is a rare autosomal dominant or recessive disorder, that involves unique bilateral craniofacial malformations. The phenotypes of TCS are extremely diverse. Interventional surgery can improve hearing loss and facial deformity in TCS patients. METHOD: We recruited seven TCS families. Variant screening in probands was performed by targeted next-generation sequencing (NGS). The variants identified were confirmed by Sanger sequencing. The pathogenicity of all the mutations was evaluated using the guidelines of the American College of Medical Genetics and Genomics (ACMG) and InterVar software. RESULTS: Three frameshift variants, two nonsense variants, one missense variant, and one splicing variant of TCOF1 were identified in the seven TCS probands. Five variants including c.1393C > T, c.4111 + 5G>C, c.1142delC, c.2285_2286delCT, and c.1719delG had not been previously reported. Furthermore, we report the c.149A > G variant for the first time in a Chinese TCS patient. We provided prenatal diagnosis for family 4. Proband 7 chose interventional surgery. CONCLUSION: We identified five novel variants in TCOF1 in Chinese patients with TCS, which expands the mutation spectrum of TCOF1 in TCS. Bone conduction hearing rehabilitation can improve hearing for TCS patients and prenatal diagnosis can provide fertility guidance for TCS families.

CRISPR/Cas9-mediated knockout and overexpression studies reveal a role of maize phytochrome C in regulating flowering time and plant height.

Maize is a major staple crop widely used for food, feedstocks and industrial products. Shade-avoidance syndrome (SAS), which is triggered when plants sense competition of light from neighbouring vegetation, is detrimental for maize yield production under high-density planting conditions. Previous studies have shown that the red and far-red photoreceptor phytochromes are responsible for perceiving the shading signals and triggering SAS in Arabidopsis; however, their roles in maize are less clear. In this study, we examined the expression patterns of ZmPHYC1 and ZmPHYC2 and found that ZmPHYC1, but not ZmPHYC2, is highly expressed in leaves and is regulated by the circadian clock. Both ZmPHYC1 and ZmPHYC2 proteins are localized to both the nucleus and cytoplasm under light conditions and both of them can interact with themselves or with ZmPHYBs. Heterologous expression of ZmPHYCs can complement the Arabidopsis phyC-2 mutant under constant red light conditions and confer an attenuated SAS in Arabidopsis in response to shading. Double knockout mutants of ZmPHYC1 and ZmPHYC2 created using the CRISPR/Cas9 technology display a moderate early-flowering phenotype under long-day conditions, whereas ZmPHYC2 overexpression plants exhibit a moderately reduced plant height and ear height. Together, these results provided new insight into the function of ZmPHYCs and guidance for breeding high-density tolerant maize cultivars.

Identification of two novel pathogenic variants of PIBF1 by whole exome sequencing in a 2-year-old boy with Joubert syndrome.

BACKGROUND: Joubert syndrome (OMIM 213300) is an autosomal recessive disorder with gene heterogeneity. Causal genes and their variants have been identified by sequencing or other technologies for Joubert syndrome subtypes. CASE PRESENTATION: A two-year-old boy was diagnosed with Joubert syndrome by global development delay and molar tooth sign of mid-brain. Whole exome sequencing was performed to detect the causative gene variants in this individual, and the candidate pathogenic variants were verified by Sanger sequencing. We identified two pathogenic variants (NM_006346.2: c.1147delC and c.1054A > G) of PIBF1 in this Joubert syndrome individual, which is consistent with the mode of autosomal recessive inheritance. CONCLUSION: In this study, we identified two novel pathogenic variants in PIBF1 in a Joubert syndrome individual using whole exome sequencing, thereby expanding the PIBF1 pathogenic variant spectrum of Joubert syndrome.

Mechanistic Investigation of a Self-Assembling Peptide against Escherichia coli.

Because of their distinctive mode of action in targeting bacterial cell membranes, antimicrobial peptides (AMPs) are increasingly regarded as a potential candidate for the development of novel antibiotics to combat the wide spread of bacterial resistance. To date, understanding of the exact molecular process by which AMPs act on the real bacterial envelope remains challenging. Simultaneously, the aggregated state of AMPs upon interaction with bacterial envelopes is still elusive. Previously, we have demonstrated that the potent antibacterial activity of a designed surfactant-like peptide Ac-A9K-NH2 benefited greatly from its high self-assembling ability and appropriate self-assembled morphologies and sizes. By using high-resolution atomic force microscopy, we here not only follow the variations of the Escherichia coli cell envelope in the presence of Ac-A9K-NH2 but also characterize the peptide aggregates on the bacterial surface as well as on the substrate surface. The results, together with those from fluorescence, zeta potential, circular dichroism, and scanning electron microscopy measurements, indicate that both the positively charged peptide monomers and self-assembled nanostructures can directly act on the negatively charged bacterial surface, followed by their insertion into the bacterial membrane, the formation of surface nanopores, and membrane lysis. The mechanism of Ac-A9K-NH2 against E. coli is thus consistent with the detergent-like mode of action. This work enhances our mechanistic understanding of the antibacterial behaviors of self-assembling peptides that will be valuable in exploring their biomedical applications.

Effects of salts on the self-assembly behavior and antibacterial activity of a surfactant-like peptide.

Self-assembling peptides have become one of the most promising antibacterial agents due to their superior properties, such as simple molecular composition, favorable assembly structures, and rich designability. For maximum application in vivo, their activities in the presence of salts are desirable, however, the potent correlation between peptide nanostructures, antibacterial activity, and salt resistance behavior remains poorly explored. Previously, we have demonstrated that the potent antibacterial activity of a designed surfactant-like peptide Ac-A9K-NH2 benefited from its high self-assembly ability and appropriate size of its self-assembled nanostructures. In this study, we investigated the effect of salts on its self-assembly behavior and antibacterial activity. The results indicated that the flexible and long nanofibrils formed by Ac-A9K-NH2 in the presence of CaCl2 were adverse to its membrane insertion, leading to the reduction of antibacterial activity. Comparatively, Ac-A9K-NH2 maintained its potent antibacterial activity in the presence of NaCl due to its suitable shape and size of nanostructures. The newly formed nanofibers and nanorods facilitated the penetration of peptides into the bacterial membrane, forming nanopores and eventually leading to the lysis of bacteria. The high antibacterial activity and NaCl tolerance of Ac-A9K-NH2 make it a promising antibacterial agent at elevated salt concentrations.

Interspecific genetic maps in Miscanthus floridulus and M. sacchariflorus accelerate detection of QTLs associated with plant height and inflorescence.

Miscanthus is recognized as a promising lignocellulosic crop for the production of bioethanol and bioproducts worldwide. To facilitate the identification of agronomical important traits and establish genetics knowledge, two genetic maps were developed from a controlled interspecific cross between M. floridulus and M. sacchariflorus. A total of 650 SSR markers were mapped in M. floridulus, spanning 19 linkage groups and 2053.31 cM with an average interval of 3.25 cM. The map of M. sacchariflorus comprised 495 SSR markers in 19 linkage groups covering 1684.86 cM with an average interval of 3.54 cM. The estimation on genome length indicated that the genome coverage of parental genetic maps were 93.87% and 89.91%, respectively. Eighty-eight bi-parental common markers were allowed to connect the two maps, and six pairs of syntenic linkage groups were recognized. Furthermore, quantitative trait loci (QTL) mapping of three agronomic traits, namely, plant height (PH), heading time (HT), and flowering time (FT), demonstrated that a total of 66 QTLs were identified in four consecutive years using interval mapping and multiple-QTL model. The LOD value of these QTLs ranged from 2.51 to 10.60, and the phenotypic variation explained varied from 9.50 to 37.10%. QTL cluster in syntenic groups MF19/MS7 contained six stable QTLs associated with PH, HT, and FT. In conclusion, we report for the first time the genetic mapping of biomass traits in M. floridulus and M. sacchariflorus. These results will be a valuable genetic resource, facilitating the discovery of essential genes and breeding of Miscanthus.

Neisseria chenwenguii sp. nov. isolated from the rectal contents of a plateau pika (Ochotona curzoniae).

Two Gram-stain negative, catalase positive, coccus shaped bacteria, designated 10023T and 10010, were isolated from the rectal contents of a plateau pika (Ochotona curzoniae) in Qinghai-Tibet Plateau, China. Based on 16S rRNA gene sequence analysis, phylogenetic trees showed that these two isolates (10023T, 10010) group with members of the genus Neisseria. Additionally, these two isolates exhibited high 16S rRNA gene sequence similarity with Neisseria zalophi CSL 7565T (96.98%), Neisseria wadsworthii WC 05-9715T (96.92%) and Neisseria canis ATCC 14687T (96.79%). Further phylogenetic analysis based on the rplF gene showed that these two novel strains can be easily discriminated from phylogenetically closely related species. Optimal growth was found to occur on BHI agar with 5% defibrinated sheep blood at 37 °C and growth was also observed on nutrient agar, Columbia blood agar and chocolate agar plates; however, growth was not observed on MacConkey agar after 7 days. The major cellular fatty acids of these strains were identified as C16:0 and C16:1ω7c/C16:1ω6c. The complete genome size of the type strain 10023T is 2,496,444 bp, with DNA G+C content of 54.0 mol %. The average nucleotide identity values were 73.5-79.3% between isolate 10023T and reference Neisseria spp. Based on polyphasic analysis, these isolates (10023T and 10010) are considered to represent a novel species in the genus Neisseria, for which the name Neisseria chenwenguii sp. nov. is proposed. The type strain is 10023T (= DSM 103440T = CGMCC 1.15736T).

Origin and domestication of papaya Yh chromosome.

Sex in papaya is controlled by a pair of nascent sex chromosomes. Females are XX, and two slightly different Y chromosomes distinguish males (XY) and hermaphrodites (XY(h)). The hermaphrodite-specific region of the Y(h) chromosome (HSY) and its X chromosome counterpart were sequenced and analyzed previously. We now report the sequence of the entire male-specific region of the Y (MSY). We used a BAC-by-BAC approach to sequence the MSY and resequence the Y regions of 24 wild males and the Y(h) regions of 12 cultivated hermaphrodites. The MSY and HSY regions have highly similar gene content and structure, and only 0.4% sequence divergence. The MSY sequences from wild males include three distinct haplotypes, associated with the populations' geographic locations, but gene flow is detected for other genomic regions. The Y(h) sequence is highly similar to one Y haplotype (MSY3) found only in wild dioecious populations from the north Pacific region of Costa Rica. The low MSY3-Y(h) divergence supports the hypothesis that hermaphrodite papaya is a product of human domestication. We estimate that Y(h) arose only ∼ 4000 yr ago, well after crop plant domestication in Mesoamerica >6200 yr ago but coinciding with the rise of the Maya civilization. The Y(h) chromosome has lower nucleotide diversity than the Y, or the genome regions that are not fully sex-linked, consistent with a domestication bottleneck. The identification of the ancestral MSY3 haplotype will expedite investigation of the mutation leading to the domestication of the hermaphrodite Y(h) chromosome. In turn, this mutation should identify the gene that was affected by the carpel-suppressing mutation that was involved in the evolution of males.

OsASR2 regulates the expression of a defence-related gene, Os2H16, by targeting the GT-1 cis-element.

The GT-1 cis-element widely exists in many plant gene promoters. However, the molecular mechanism that underlies the response of the GT-1 cis-element to abiotic and biotic stresses remains elusive in rice. We previously isolated a rice short-chain peptide-encoding gene, Os2H16, and demonstrated that it plays important roles in both disease resistance and drought tolerance. Here, we conducted a promoter assay of Os2H16 and identified GT-1 as an important cis-element that mediates Os2H16 expression in response to pathogen attack and osmotic stress. Using the repeated GT-1 as bait, we characterized an abscisic acid, stress and ripening 2 (ASR2) protein from yeast-one hybridization screening. Sequence alignments showed that the carboxy-terminal domain of OsASR2 containing residues 80-138 was the DNA-binding domain. Furthermore, we identified that OsASR2 was specifically bound to GT-1 and activated the expression of the target gene Os2H16, as well as GFP driven by the chimeric promoter of 2 × GT-1-35S mini construct. Additionally, the expression of OsASR2 was elevated by pathogens and osmotic stress challenges. Overexpression of OsASR2 enhanced the resistance against Xanthomonas oryzae pv. oryzae and Rhizoctonia solani, and tolerance to drought in rice. These results suggest that the interaction between OsASR2 and GT-1 plays an important role in the crosstalk of the response of rice to biotic and abiotic stresses.

Actinomyces tangfeifanii sp. nov., isolated from the vulture Aegypius monachus.

A novel, Gram-stain-positive, catalase-positive, non-spore-forming, short rod-shaped strain (VUL4_3T) was isolated from rectal swabs of Old World vultures (Aegypius monachus) from the Tibet-Qinghai Plateau, China. Based on the results of biochemical tests and 16S rRNA gene sequence comparison, strain VUL4_3T was determined to be a member of the genus Actinomyces that is closely related to the type strains of Actinomyces liubingyangii (97.7 % 16S rRNA gene sequence similarity) and Actinomyces marimammalium (96.5 %). Optimal growth occurred at 37 °C, pH 6-7 and with 1 % (w/v) NaCl. The typical major cellular fatty acids of strain VUL4_3T were C18 : 1ω9c, C16 : 0 and C18 : 0. The VUL4_3T genome contained 2 207 832 bp with an average G+C content of 51.9 mol%. DNA-DNA hybridization values between strain VUL4_3T and the above two species of the genus Actinomyces showed less than 32 % DNA-DNA relatedness, supporting a novel species status of strain VUL4_3T. Based on the phenotypic data and phylogenetic inference, the novel species Actinomycestangfeifanii sp. nov. is proposed. The type strain is VUL4_3T (=CGMCC 4.7369T=DSM 103436T).

Rational Design of Short Peptide-Based Hydrogels with MMP-2 Responsiveness for Controlled Anticancer Peptide Delivery.

Molecular self-assembly makes it feasible to harness the structures and properties of advanced materials via initial molecular design. To develop short peptide-based hydrogels with stimuli responsiveness, we designed here short amphiphilic peptides by engineering protease cleavage site motifs into self-assembling peptide sequences. We demonstrated that the designed Ac-I3SLKG-NH2 and Ac-I3SLGK-NH2 self-assembled into fibrillar hydrogels and that the Ac-I3SLKG-NH2 hydrogel showed degradation in response to MMP-2 but the Ac-I3SLGK-NH2 hydrogel did not. The cleavage of Ac-I3SLKG-NH2 into Ac-I3S and LKG-NH2 was found to be mechanistically responsible for the enzymatic degradation. Finally, when an anticancer peptide G(IIKK)3I-NH2 (G3) was entrapped into Ac-I3SLKG-NH2 hydrogels, its release was revealed to occur in a "cell-demanded" way in the presence of HeLa cells that overexpress MMP-2, therefore leading to a marked inhibitory effect on their growth on the gels.

Streptococcus himalayensis sp. nov., isolated from the respiratory tract of Marmota himalayana.

Five strains of Gram-positive-staining, catalase-negative, coccus-shaped, chain-forming organisms isolated separately from the respiratory tracts of five Marmota himalayana animals in the Qinghai-Tibet Plateau of China were subjected to phenotypic and molecular taxonomic analyses. Comparative analysis of the 16S rRNA gene indicated that these singular organisms represent a new member of the genus Streptococcus, being phylogenetically closest to Streptococcus marmotae DSM 101995T (98.4 % similarity). The groEL, sodA and rpoB sequence analysis showed interspecies similarity values between HTS2T and Streptococcus. marmotae DSM 101995T, its closest phylogenetic relative based on 16S rRNA gene sequences, of 98.2, 78.8 and 93.7 %, respectively. A whole-genome phylogenetic tree built from 82 core genes of genomes from 16 species of the genus Streptococcus validated that HTS2T forms a distinct subline and exhibits specific phylogenetic affinity with S. marmotae. In silico DNA-DNA hybridization of HTS2T showed an estimated DNA reassociation value of 40.5 % with Streptococcus. marmotae DSM 101995T. On the basis of their phenotypic characteristics and phylogenetic findings, it is proposed that the five isolates be classified as representatives of a novel species of the genus Streptococcus, Streptococcus himalayensis sp. nov. The type strain is HTS2T (=DSM 101997T=CGMCC 1.15533T). The genome of Streptococcus himalayensis sp. nov. strain HTS2T contains 2195 genes with a size of 2 275 471 bp and a mean DNA G+C content of 41.3 mol%.

Streptococcusmarmotae sp. nov., isolated from the respiratory tract of Marmota himalayana.

Five strains of a Gram-stain-positive, catalase-negative, α-haemolytic, coccus-shaped chain-forming organism were isolated separately from the lower respiratory tracts of five animals of Marmota himalayana in the endemic area of plague, the Qinghai-Tibet Plateau, China. Based on their morphological characteristics, biochemical features and molecular phylogenetic studies, the strains were placed as representing a new member of the genus Streptococcus. Comparative 16S rRNA gene sequence studies indicated that strain HTS5T shared 96.5, 96.2 and 96.0 % similarity with Streptococcus gallinaceus CCUG 42692T, Streptococcus parasanguinis ATCC 15912T and Streptococcus suis ATCC 43765T, respectively. Sequence analysis of its rpoB and sodA genes showed that strain HTS5T was most closely related to Streptococcus cuniculi CCUG 65085T with 9.2 and 10.9 % interspecies divergence, respectively. The whole genome phylogenetic tree based on 339 core genes of 65 Streptococcus genomes confirmed that HTS5T belongs to a distinct lineage that is well separated from recognized species of the genus Streptococcus. In silico DNA-DNA hybridization using 65 available genomes from GenBank showed that HTS5T displayed less than 70 % DNA-DNA relatedness with the other 65 species of the genus Streptococcus deposited in the GenBank database. The genome of strain HTS5T (2 322 791 bp) contained 2377 genes and had a G+C content of 41.6 mol%. Therefore, the five strains are considered to represent a novel species of the genus Streptococcus for which the name Streptococcusmarmotae sp. nov. is proposed. The type strain is HTS5T (=DSM 101995T=CGMCC 1.15534T).

Streptococcus halotolerans sp. nov. isolated from the respiratory tract of Marmota himalayana in Qinghai-Tibet Plateau of China.

Two Gramstaining-positive, catalase-negative, α-hemolytic, coccus-shaped organisms were isolated separately from the respiratory tracts of two Marmota himalayana animals from the Qinghai-Tibet Plateau, PR China. Morphological, biological, biochemical, and molecular genetic studies were performed on these two isolates (HTS9T and HTS12). Their biochemical characteristics, such as acid production from different sugars and enzymatic activities, indicated that they represented a member of the genus Streptococcus. They are most closely related to Streptococcus thoraltensis CIP 105518T based on sequence analysis of their 16S rRNA, groEL, sodA and rpoB genes, with similarities of 97.6, 89.9, 92.6 and 91.1 % the four genes respectively. The whole genome phylogenetic tree reconstructed using 372 core genes from 65 genomes of members of the genus Streptococcus validates that HTS9T forms a distinct subline and exhibits specific phylogenetic affinity with S. thoraltensis. In silico DNA-DNA hybridization of HTS9T showed a DNA reassociation value of 32.1 %, closest to that of S. thoraltensis CIP 105518T. Based on their phenotypic characteristics and in particular the phylogenetic findings (DNA-DNA hybridization, three phylogenetic trees built from the partial 16S rRNA/housekeeping genes, and from 372 core genes of 65 genomes of members of the genus Streptococcus), we propose with confidence that strains HTS9T and HTS12 should be classified as representing a novel species of the genus Streptococcus, Streptococcus halotolerans sp. nov. The type strain is HTS9T (=DSM 101996T=CGMCC1.15532T). Genome analysis of Streptococcus halotolerans sp. nov. shows that its genome is 1 823 556 bp long with a DNA G+C content of 39.9 mol% and contains 2068 genes.

Sequencing papaya X and Yh chromosomes reveals molecular basis of incipient sex chromosome evolution.

Sex determination in papaya is controlled by a recently evolved XY chromosome pair, with two slightly different Y chromosomes controlling the development of males (Y) and hermaphrodites (Y(h)). To study the events of early sex chromosome evolution, we sequenced the hermaphrodite-specific region of the Y(h) chromosome (HSY) and its X counterpart, yielding an 8.1-megabase (Mb) HSY pseudomolecule, and a 3.5-Mb sequence for the corresponding X region. The HSY is larger than the X region, mostly due to retrotransposon insertions. The papaya HSY differs from the X region by two large-scale inversions, the first of which likely caused the recombination suppression between the X and Y(h) chromosomes, followed by numerous additional chromosomal rearrangements. Altogether, including the X and/or HSY regions, 124 transcription units were annotated, including 50 functional pairs present in both the X and HSY. Ten HSY genes had functional homologs elsewhere in the papaya autosomal regions, suggesting movement of genes onto the HSY, whereas the X region had none. Sequence divergence between 70 transcripts shared by the X and HSY revealed two evolutionary strata in the X chromosome, corresponding to the two inversions on the HSY, the older of which evolved about 7.0 million years ago. Gene content differences between the HSY and X are greatest in the older stratum, whereas the gene content and order of the collinear regions are identical. Our findings support theoretical models of early sex chromosome evolution.

Surface properties of nucleolipids and photo-controlled release of hydrophobic guest molecules from their micellar aggregates.

Two series of nucleolipids have been designed and synthesized, one with a varying chain length (the dT-Cn series) and the other incorporating an aromatic photo-responsive moiety at the molecular hydrophobic and hydrophilic interface (the P-dT-Cn series). Surface tension measurements revealed the variations of critical micelle concentrations (CMCs) with the alkyl chain length and the incorporation of the photo-responsive segment. The P-dT-Cn series showed broadly lower CMCs and the minimum area per molecule (Amin) values because the π-π stacking between the additional aromatic rings favours more tight packing in the micelle formation. Both series showed similar surface tensions at the CMCs to conventional surfactants with equivalent molecular structures. Their micellar aggregates were used for encapsulation of hydrophobic Nile Red (NR). For the P-dT-Cn series, the encapsulated NR was released upon light irradiation and the controlled release was readily realized by controlling irradiation intensities or switching on and off irradiation. The integration of biocompatibility, complementary base recognition and photo-responsiveness makes the amphiphilic nucleolipids promising in biomedical and biotechnological applications.