Novel Mechanisms Underlying Rubber Accumulation and Programmed Cell Death in Laticiferous Canals of Decaisnea insignis Fruits: Cytological and Transcriptomic Analyses.

Natural rubber is one of the most important industrial raw materials, and its biosynthesis is still a fascinating process that is still largely unknown. In this research, we studied Decaisnea insignis, a unique rubber-producing plant that is different from other rubber-producing species due to the presence of lactiferous canals in its pericarp. The present study aims to provide novel insights into the mechanisms underlying rubber accumulation and PCD by subjecting the Decaisnea insignis laticiferous canals to light microscopy, TUNEL assay, and DAPI staining, as well as viability analysis, cellular ultrastructure analysis, and molecular analysis using light microscopy, scanning electron microscopy, immunofluorescence labeling, transmission electron microscopy, and transcriptome sequencing. At the cellular level, the origin of small rubber particles in the laticiferous canals had no morphological correlation with other organelles, and these particles were freely produced in the cytosol. The volume of the rubber particles increased at the sunken and expanding stage, which were identified as having the characteristics of programmed cell death (PCD); meanwhile, plenty of the rubber precursors or rubber particles were engulfed by the vacuoles, indicating a vacuole-mediated autophagy process. The accumulation of rubber particles occurred after the degeneration of protoplasts, suggesting a close association between rubber biosynthesis and PCD. The molecular analysis revealed the expression patterns of key genes involved in rubber biosynthesis. The upstream genes DiIPP, DiFPP, and DiGGPPS showed a decreasing trend during fruit ripening, while DiHRT, which is responsible for rubber particle extension, exhibited the highest expression level during the rubber particle formation. Moreover, the transcription factors related to PCD, DiLSD1, and DiLOL2 showed a negative correlation with the expression pattern of DiHRT, thus exhibiting strict rules of sequential expression during rubber biosynthesis. Additionally, the expression trends of DiXCP1 and DiCEP1, which act as proteases during PCD, were positively correlated with DiGGPPS expression. In conclusion, the findings suggest that the autophagic PCD may play a crucial role in rubber accumulation in D. insignis. Further research is still needed to fully understand the complex regulatory network underlying rubber biosynthesis in plants.

Developmental Programmed Cell Death Involved in Ontogenesis of Dictamnus dasycarpus Capitate Glandular Hairs.

Plant glandular trichomes have received much attention due to their commercial and biological value. Recent studies have focused on the development of various glands in plants, suggesting that programmed cell death (PCD) may play an important role during the development of plant secretory structures. However, the development processes and cytological characteristics in different types of plant secretory structures differed significantly. This study aims to provide new data on the developmental PCD of the capitate glandular hairs in Dictamnus dasycarpus. Light, scanning, immunofluorescence labeling, and transmission electron microscopy were used to determine the different developmental processes of the capitate glandular hairs from a cytological perspective. Morphologically, the capitate glandular hair originates from one initial epidermal cell and differentiates into a multicellular trichome characterized by two basal cells, two lines of stalk cells, and a multicellular head. It is also histochemically detected by essential oils. TUNEL-positive reactions identified nuclei with diffused fluorescence or an irregular figure by DAPI, and Evans blue staining showed that the head and stalk cells lost their viability. Ultrastructural evidence revealed the developmental process by two possible modes of PCD. Non-autolytic PCD was characterized by buckling cell walls and degenerated nuclei, mitochondria, plastids, multivesicular body (MVB), and end-expanded endoplasmic reticulum in the condensed cytoplasm, which were mainly observed in the head cells. The MVB was detected in the degraded vacuole, a degraded nucleus with condensed chromatin and diffused membrane, and eventual loss of the vacuole membrane integrity exhibited typical evidence of vacuole-mediated autolytic PCD in the stalk cells. Furthermore, protoplasm degeneration coupled with dark oil droplets and numerous micro-dark osmiophilic substances was observed during late stages. The secretion mode of essential oils is also described in this paper.

The Evolutionary Patterns of Genome Size in Ensifera (Insecta: Orthoptera).

Genomic size variation has long been a focus for biologists. However, due to the lack of genome size data, the mechanisms behind this variation and the biological significance of insect genome size are rarely studied systematically. The detailed taxonomy and phylogeny of the Ensifera, as well as the extensive documentation concerning their morphological, ecological, behavioral, and distributional characteristics, make them a strong model for studying the important scientific problem of genome size variation. However, data on the genome size of Ensifera are rather sparse. In our study, we used flow cytometry to determine the genome size of 32 species of Ensifera, the smallest one being only 1C = 0.952 pg with the largest species up to 1C = 19.135 pg, representing a 20-fold range. This provides a broader blueprint for the genome size variation of Orthoptera than was previously available. We also completed the assembly of nine mitochondrial genomes and combined mitochondrial genome data from public databases to construct phylogenetic trees containing 32 species of Ensifera and three outgroups. Based on these inferred phylogenetic trees, we detected the phylogenetic signal of genome size variation in Ensifera and found that it was strong in both males and females. Phylogenetic comparative analyses revealed that there were no correlations between genome size and body size or flight ability in Tettigoniidae. Reconstruction of ancestral genome size revealed that the genome size of Ensifera evolved in a complex pattern, in which the genome size of the grylloid clade tended to decrease while that of the non-grylloid clade expanded significantly albeit with fluctuations. However, the evolutionary mechanisms underlying variation of genome size in Ensifera are still unknown.

Remarks on the genus Dolicholobosa Bian, Zhu amp; Shi, 2017 (Orthoptera: Tettigoniidae: Meconematinae) with one new species from Guizhou, China.

The paper reports one new species of the genus Dolicholobosa Bian, Zhu Shi, 2017 from Leigongshan, Guizhou, China, i.e. Dolicholobosa bisofurcula sp. nov., and provides the high-quality multifocused montage images of the new species, two known species and distribution map for the genus.

Comparative mitochondrial genomics of Shoveliteratura triangula (Orthoptera, Tettigoniidae, Meconematinae) and the first description of a female specimen.

This paper provides the first description of a female of Shoveliteratura triangula Shi, Bian Change, 2011, as well as the complete mitogenome sequence using next-generation sequencing (NGS) technology. The length of the entire mitogenome was 16,152 bp and contained the typical gene arrangement, base composition, and codon usage found in other related species. The overall base composition exhibited a clear anti-G (10.8%) and AT bias (70.5%). The third codon positions in all protein-coding genes (PCGs) displayed high AT-content values (81.4%) in contrast to lower values of 64.2%/64.5% in the first/second positions. Two tandem repeats, 2.49 repeats of 112 bp and 3.65 repeats of 201 bp, contributed 1013 bp to the length of the S. triangula control region (CR). A T-stretch as a recognition sequence of the replication origin and more than one distinct tandem repeat in the CR were common in the Tettigoniidae mitogenomes. Both the maximum likelihood (ML) and Bayesian inference (BI) analyses supported each subfamily of the Tettigoniidae as a monophyletic group. The relationships of the subfamilies were as follows: (Lipotactinae (Hexacentrinae (Conocephalinae (Meconematinae (Bradyporinae, Tettigoniinae))))). The newly sequenced species S. triangula was most closely related to Pseudokuzicus pieli.

One new species of the genus Xizicus Gorochov, 1993 (Orthoptera: Tettigoniidae: Meconematinae) from Guangxi, China.

One new species of the genus Xizicus Gorochov, 1993 is described, namely Xizicus (Eoxizicus) lobicercus sp. nov. from China. In addition, morphological photograph of Xizicus (Eoxizicus) divergrntis (Liu Zhang, 2000) are provided. All the type specimens are deposited in the Museum of Hebei University.

Mitochondrial genome of a brachypterous species in Meconematinae: Acosmetura nigrogeniculata and its phylogenetic implication.

Acosmetura nigrogeniculata (Liu and Wang, 1998) is a brachypterous species in Meconematinae, which is only distributed in China. In this study, the complete mitochondrial genome of A. nigrogeniculata was determined and annotated. The 16,271 bp circular genome contained 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and one control region. The overall base composition was 36.4% A, 34.8% T, 18.4% C, and 10.5% G, exhibiting obvious anti-G and AT bias (71.2%). The general genomic characters including nucleotides composition, gene arrangement, and codon usage were similar to those of other Meconematinae species. Phylogenetic analysis of all nine Meconematinae species indicated that the newly sequenced species were clustered closely with the brachypterous species Pseudosmetura snjiensis.

The complete chloroplast genome sequence of Campylandra chinensis (Liliaceae).

The complete chloroplast genome of Campylandra chinensis from China was analyzed using next-generation sequencing. The chloroplast genome was a 169,419 bp circular molecule and was predicted to contain a large single copy (LSC) of 86,752 bp and a small single copy (SSC) of 21,363 bp, which were separated by a pair of 25,340 bp inverted repeats (IRs). A total of 132 unique genes were annotated, including 86 protein coding genes, 38 tRNA genes, and 8 rRNA genes. Among these genes, 19 genes contained one or two introns. The overall GC contents of the plastid genome was 37.2%. Phylogenetic analysis showed that C. chinensis and Polygonatum species clustered to one clade with a high bootstrap value at the base of the phylogenetic tree.

Review of the subgenus Xizicus (Xizicus) Gorochov, 1993 (Orthoptera: Tettigoniidae: Meconematinae) from China.

Gorochov (1993) erected the subgenus Xizicus (Xizicus), with the type species Xizicus (Xizicus) fascipes (Bey-Bienko, 1955). This subgenus is distinguished from the other subgenera of Xizicus by the following characters: male tenth abdominal tergite with a pair of contiguous posterior processes in the middle; subgenital plate simple, styli slender, located on the apices or subapices of lateral margins; posterior margin of female subgenital plate rounded.

Characterization of the mitochondrial genome of Phyllomimus sp. (Orthoptera: Pseudophyllidae).

The nearly complete mitochondrial genome (mitogenome) without tRNA-Met and with a partial A + T-rich region of phyllomimus sp. has been sequenced with the length of 15,543 bp. We found 140 bp-long intergenic spacers (IGSs) which located between tRNA-Gln and ND2, while this region should be tRNA-Met in most orthopteran mitogenomes. The content of As, Ts, Cs Gs and AT in the mitogenome is 37.3%, 32.5%, 20.6%, 9.5% and 69.8%, respectively. All protein-coding genes start with typical ATN codon except for ND1, which initiates with TTG codon instead, and end with either complete TAA/TAG codons or incomplete T(aa) codons. Phylogenetic analysis indicated that genetic distances of phyllomimus sp. and Orophyllus montanus was closer than other species.

Two new species of the genus Xizicus (Orthoptera: Tettigoniidae: Meconematinae) in China.

Two new species of the genus Xizicus are described, namely Xizicus (Eoxizicus) uncicercus Mao & Shi sp. nov. and Xizicus (Eoxizicus) dischidus Di, Han & Shi sp. nov. from China, in addition, photographs of morphological structure of the species are provided. All type specimens are deposited in the Museum of Hebei University, Baoding, P. R. China.

Review of the genus Pentacentrus Saussure (Orthoptera: Gryllidae: Pentacentrinae) from China .

Four new species of Pentacentrus Gorochov from China are described and illustrated, P. acutiparamerus Liu & Shi sp. nov., P. biflexuous Liu & Shi sp. nov., P. emarginatus Liu & Shi sp. nov. and P. parvulus Liu & Shi sp. nov. A key and a distribution map of the Chinese species of this genus are provided.

Two new species of the genus Euxiphidiopsis Gorochov, 1993 (Orthoptera: Meconematinae) from China.

The article reported two new species of the genus Euxiphidiopsis Gorochov, 1993, i.e. Euxiphidiopsis erromena Shi & Mao sp. nov., and Euxiphidiopsis damingshanensis sp. nov. The type material is deposited in the Museum of Hebei University, Baoding, P. R. China.

Programmed cell death: a mechanism for the lysigenous formation of secretory cavities in leaves of Dictamnus dasycarpus.

The formation of secretory cavities in Rutaceae has been the subject of great interest. In this study, cytological events that are involved in the lysigenous formation of the secretory cavities in the leaves of Dictamnus dasycarpus are characterized by an interesting pattern of programmed cell death (PCD). During the developmental process, clusters of cells from a single protoepidermal cell embark on different trajectories and undergo different cell death fates: the cell walls of the secretory cells have characteristics of thinning or complete breakdown, while the sheath cells present a predominantly thick-walled feature. A DAPI assay shows deformed nuclei that are further confirmed to be TUNEL-positive. Gel electrophoresis indicates that DNA cleavage is random and does not result in ladder-like DNA fragmentation. Ultrastructurally, several remarkable features of PCD have been determined, such as misshapen nuclei with condensed chromatin and a significantly diffused membrane, degenerated mitochondria and plastids with disturbed membrane systems, multivesicular bodies, plastolysomes, vacuole disruption and lysis of the center secretory cell. Cytological evidence and Nile red stains exhibit abundant essential oils accumulated in degenerated outer secretory cells after the dissolution of the center secretory cell. In addition, explanations of taxonomic importance and the relationship between PCD and oil droplet accumulation in the secretory cavities are also discussed.

DNA barcoding and species boundary delimitation of selected species of Chinese Acridoidea (Orthoptera: Caelifera).

We tested the performance of DNA barcoding in Acridoidea and attempted to solve species boundary delimitation problems in selected groups using COI barcodes. Three analysis methods were applied to reconstruct the phylogeny. K2P distances were used to assess the overlap range between intraspecific variation and interspecific divergence. "Best match (BM)", "best close match (BCM)", "all species barcodes (ASB)" and "back-propagation neural networks (BP-based method)" were utilized to test the success rate of species identification. Phylogenetic species concept and network analysis were employed to delimitate the species boundary in eight selected species groups. The results demonstrated that the COI barcode region performed better in phylogenetic reconstruction at genus and species levels than at higher-levels, but showed a little improvement in resolving the higher-level relationships when the third base data or both first and third base data were excluded. Most overlaps and incorrect identifications may be due to imperfect taxonomy, indicating the critical role of taxonomic revision in DNA barcoding study. Species boundary delimitation confirmed the presence of oversplitting in six species groups and suggested that each group should be treated as a single species.