Mutation mapping of a variegated EMS tomato reveals an FtsH-like protein precursor potentially causing patches of four phenotype classes in the leaves with distinctive internal morphology.

BACKGROUND: Leaf variegation is an intriguing phenomenon observed in many plant species. However, questions remain on its mechanisms causing patterns of different colours. In this study, we describe a tomato plant detected in an M2 population of EMS mutagenised seeds, showing variegated leaves with sectors of dark green (DG), medium green (MG), light green (LG) hues, and white (WH). Cells and tissues of these classes, along with wild-type tomato plants, were studied by light, fluorescence, and transmission electron microscopy. We also measured chlorophyll a/b and carotene and quantified the variegation patterns with a machine-learning image analysis tool. We compared the genomes of pooled plants with wild-type-like and mutant phenotypes in a segregating F2 population to reveal candidate genes responsible for the variegation. RESULTS: A genetic test demonstrated a recessive nuclear mutation caused the variegated phenotype. Cross-sections displayed distinct anatomy of four-leaf phenotypes, suggesting a stepwise mesophyll degradation. DG sectors showed large spongy layers, MG presented intercellular spaces in palisade layers, and LG displayed deformed palisade cells. Electron photomicrographs of those mesophyll cells demonstrated a gradual breakdown of the chloroplasts. Chlorophyll a/b and carotene were proportionally reduced in the sectors with reduced green pigments, whereas white sectors have hardly any of these pigments. The colour segmentation system based on machine-learning image analysis was able to convert leaf variegation patterns into binary images for quantitative measurements. The bulk segregant analysis of pooled wild-type-like and variegated progeny enabled the identification of SNP and InDels via bioinformatic analysis. The mutation mapping bioinformatic pipeline revealed a region with three candidate genes in chromosome 4, of which the FtsH-like protein precursor (LOC100037730) carries an SNP that we consider the causal variegated phenotype mutation. Phylogenetic analysis shows the candidate is evolutionary closest to the Arabidopsis VAR1. The synonymous mutation created by the SNP generated a miRNA binding site, potentially disrupting the photoprotection mechanism and thylakoid development, resulting in leaf variegation. CONCLUSION: We described the histology, anatomy, physiology, and image analysis of four classes of cell layers and chloroplast degradation in a tomato plant with a variegated phenotype. The genomics and bioinformatics pipeline revealed a VAR1-related FtsH mutant, the first of its kind in tomato variegation phenotypes. The miRNA binding site of the mutated SNP opens the way to future studies on its epigenetic mechanism underlying the variegation.

Twelve newly assembled jasmine chloroplast genomes: unveiling genomic diversity, phylogenetic relationships and evolutionary patterns among Oleaceae and Jasminum species.

BACKGROUND: Jasmine (Jasminum), renowned for its ornamental value and captivating fragrance, has given rise to numerous species and accessions. However, limited knowledge exists regarding the evolutionary relationships among various Jasminum species. RESULTS: In the present study, we sequenced seven distinct Jasminum species, resulting in the assembly of twelve high-quality complete chloroplast (cp) genomes. Our findings revealed that the size of the 12 cp genomes ranged from 159 to 165 kb and encoded 134-135 genes, including 86-88 protein-coding genes, 38-40 tRNA genes, and 8 rRNA genes. J. nudiflorum exhibited a larger genome size compared to other species, mainly attributed to the elevated number of forward repeats (FRs). Despite the typically conservative nature of chloroplasts, variations in the presence or absence of accD have been observed within J. sambac. The calculation of nucleotide diversity (Pi) values for 19 cp genomes indicated that potential mutation hotspots were more likely to be located in LSC regions than in other regions, particularly in genes ycf2, rbcL, atpE, ndhK, and ndhC (Pi > 0.2). Ka/Ks values revealed strong selection pressure on the genes rps2, atpA, rpoA, rpoC1, and rpl33 when comparing J. sambac with the three most closely related species (J. auriculatum, J. multiflorum, and J. dichotomum). Additionally, SNP identification, along with the results of Structure, PCA, and phylogenetic tree analyses, divided the Jasminum cp genomes into six groups. Notably, J. polyanthum showed gene flow signals from both the G5 group (J. nudiflorum) and the G3 group (J. tortuosum and J. fluminense). Phylogenetic tree analysis reflected that most species from the same genus clustered together with robust support in Oleaceae, strongly supporting the monophyletic nature of cp genomes within the genus Jasminum. CONCLUSION: Overall, this study provides comprehensive insights into the genomic composition, variation, and phylogenetic relationships among various Jasminum species. These findings enhance our understanding of the genetic diversity and evolutionary history of Jasminum.

Comparative analysis of codon usage patterns in the chloroplast genomes of nine forage legumes.

Leguminosae is one of the three largest families of angiosperms after Compositae and Orchidaceae. It is widely distributed and grows in a variety of environments, including plains, mountains, deserts, forests, grasslands, and even waters where almost all legumes can be found. It is one of the most important sources of starch, protein and oil in the food of mankind and also an important source of high-quality forage material for animals, which has important economic significance. In our study, the codon usage patterns and variation sources of the chloroplast genome of nine important forage legumes were systematically analyzed. Meanwhile, we also constructed a phylogenetic tree based on the whole chloroplast genomes and protein coding sequences of these nine forage legumes. Our results showed that the chloroplast genomes of nine forage legumes end with A/T bases, and seven identical high-frequency (HF) codons were detected among the nine forage legumes. ENC-GC3s mapping, PR2 analysis, and neutral analysis showed that the codon bias of nine forage legumes was influenced by many factors, among which natural selection was the main influencing factor. The codon usage frequency showed that the Nicotiana tabacum and Saccharomyces cerevisiae can be considered as receptors for the exogenous expression of chloroplast genes of these nine forage legumes. The phylogenetic relationships of the chloroplast genomes and protein coding genes were highly similar, and the nine forage legumes were divided into three major clades. Among the clades Melilotus officinalis was more closely related to Medicago sativa, and Galega officinalis was more closely related to Galega orientalis. This study provides a scientific basis for the molecular markers research, species identification and phylogenetic studies of forage legumes. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-024-01421-0.

The complete chloroplast genome sequence of Zanthoxylum ailanthoides Sieb. et. Zucc (Rutaceae): an important medicinal plant.

Zanthoxylum ailanthoides is a deciduous tree, with important medicinal and economic values. The complete chloroplast genome sequence of Z. ailanthoides was assembled and the phylogenetic relationship to other species was inferred in this study. The chloroplast genome is 157,209 bp in length, including two inverted repeats of 26,408 bp, a large single-copy of 86,099 bp and a small single copy of 18,294 bp. Moreover, the chloroplast genome contains 129 genes, including 84 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The overall GC content of the chloroplast genome is 38.4%. The phylogenetic analysis indicated that Z. ailanthoides was grouped with a clade containing the species of Z. multijugum, Z. calcicola, Z. oxyphyllum, Z. stenophyllum, and the genus was closely related to Phellodendron. This study contributes to a better understanding of the phylogenetic relationships among Zanthoxylum species.

The complete chloroplast genome sequence of Rhamnella wilsonii Schneid (Rhamnaceae).

Rhamnella wilsonii Schneid 1914 is a member of the Rhamnaceae and endemic to China. In this study, the complete chloroplast genome of R. wilsonii was sequenced and assembled. The complete chloroplast genome was 160,049 bp in length, including a pair of inverted repeats (IRs) of 26,502 bp, one large single copy (LSC) region of 88,274 bp and one small single copy (SSC) region of 18,771 bp. The genome contained 129 genes, including 8 rRNA genes, 37 tRNA genes and 84 protein-coding genes. The overall GC content of the complete chloroplast genome was 37.15%. The phylogenetic analysis demonstrated that R. wilsonii is closely related to R. martinni. This study provides basic information for further studies on the identification and evolution of R. wilsonii and Rhamnella from genomic perspective.

Evidence of microRNAs origination from chloroplast genome and their role in regulating Photosystem II protein N (psbN) mRNA.

The microRNAs are endogenous, regulating gene expression either at the DNA or RNA level. Despite the availability of extensive studies on microRNA generation in plants, reports on their abundance, biogenesis, and consequent gene regulation in plant organelles remain naVve. Building on previous studies involving pre-miRNA sequencing in Abelmoschus esculentus, we demonstrated that three putative microRNAs were raised from the chloroplast genome. In the current study, we have characterized the genesis of these three microRNAs through a combination of bioinformatics and experimental approaches. The gene sequence for a miRNA, designated as AecpmiRNA1 (A. esculentus chloroplast miRNA), is potentially located in both the genomic DNA, i.e., nuclear and chloroplast genome. In contrast, the gene sequences for the other two miRNAs (AecpmiRNA2 and AecpmiRNA3) are exclusively present in the chloroplast genome. Target prediction revealed many potential mRNAs as targets for AecpmiRNAs. Further analysis using 5' RACE-PCR determined the AecpmiRNA3 binding and cleavage site at the photosystem II protein N (psbN). These results indicate that AecpmiRNAs are generated from the chloroplast genome, possessing the potential to regulate mRNAs arising from chloroplast gene(s). On the other side, the possibility of nuclear genome-derived mRNA regulation by AecpmiRNAs cannot be ruled out.

Extraction and analysis of high-quality chloroplast DNA with reduced nuclear DNA for medicinal plants.

BACKGROUND: Obtaining high-quality chloroplast genome sequences requires chloroplast DNA (cpDNA) samples that meet the sequencing requirements. The quality of extracted cpDNA directly impacts the efficiency and accuracy of sequencing analysis. Currently, there are no reported methods for extracting cpDNA from Erigeron breviscapus. Therefore, we developed a suitable method for extracting cpDNA from E. breviscapus and further verified its applicability to other medicinal plants. RESULTS: We conducted a comparative analysis of chloroplast isolation and cpDNA extraction using modified high-salt low-pH method, the high-salt method, and the NaOH low-salt method, respectively. Subsequently, the number of cpDNA copies relative to the nuclear DNA (nDNA ) was quantified via qPCR. As anticipated, chloroplasts isolated from E. breviscapus using the modified high-salt low-pH method exhibited intact structures with minimal cell debris. Moreover, the concentration, purity, and quality of E. breviscapus cpDNA extracted through this method surpassed those obtained from the other two methods. Furthermore, qPCR analysis confirmed that the modified high-salt low-pH method effectively minimized nDNA contamination in the extracted cpDNA. We then applied the developed modified high-salt low-pH method to other medicinal plant species, including Mentha haplocalyx, Taraxacum mongolicum, and Portulaca oleracea. The resultant effect on chloroplast isolation and cpDNA extraction further validated the generalizability and efficacy of this method across different plant species. CONCLUSIONS: The modified high-salt low-pH method represents a reliable approach for obtaining high-quality cpDNA from E. breviscapus. Its universal applicability establishes a solid foundation for chloroplast genome sequencing and analysis of this species. Moreover, it serves as a benchmark for developing similar methods to extract chloroplast genomes from other medicinal plants.

Sequence characteristics, genetic diversity and phylogenetic analysis of the Cucurbita ficifolia (Cucurbitaceae) chloroplasts genome.

BACKGROUND: Curcubita ficifolia Bouché (Cucurbitaceae) has high value as a food crop and medicinal plant, and also has horticultural value as rootstock for other melon species. China is home to many different cultivars, but the genetic diversity of these resources and the evolutionary relationships among them, as well as the differences between C. ficifolia and other Cucurbita species, remain unclear. RESULTS: We investigated the chloroplast (cp) genomes of 160 C. ficifolia individuals from 31 populations in Yunnan, a major C. ficifolia production area in China. We found that the cp genome of C. ficifolia is ~151 kb and contains 128 genes, of which 86 are protein coding genes, 34 encode tRNA, and eight encode rRNAs. We also identified 64 SSRs, mainly AT repeats. The cp genome was found to contain a total of 204 SNP and 57 indels, and a total of 21 haplotypes were found in the 160 study individuals. The reverse repeat (IR) region of C. ficifolia contained a few differences compared with this region in the six other Cucurbita species. Sequence difference analysis demonstrated that most of the variable regions were concentrated in the single copy (SC) region. Moreover, the sequences of the coding regions were found to be more similar among species than those of the non-coding regions. The phylogenies reconstructed from the cp genomes of 61 representative species of Cucurbitaceae reflected the currently accepted classification, in which C. ficifolia is sister to the other Cucurbita species, however, different interspecific relationships were found between Cucurbita species. CONCLUSIONS: These results will be valuable in the classification of C. ficifolia genetic resources and will contribute to our understanding of evolutionary relationships within the genus Cucurbita.

Characterization of the complete chloroplast genome sequence of Agave durangensis (Asparagales: Asparagaceae: Agavoideae).

Agave durangensis commonly known as agave cenizo, is an endemic Agave species in Mexico used for mescal production, yet its taxonomic delimitation is still controversial. This study aimed to enhance taxonomic clarity by characterizing its chloroplast genome. Chloroplast DNA was isolated from 2-year-old A. durangensis leaves. The complete chloroplast genome size was 156,441 bp, comprising a large single-copy region (LSC), a pair of inverted repeat regions (IR), and a small single-copy region (SSC). Annotation revealed 87 protein-coding genes, 38 tRNAs, and 8 rRNAs, with notable gene inversions. Phylogenetic analysis suggests, A. durangensis forms a separate lineage within the Agave genus.

The complete chloroplast genome and phylogentic results support the species position of Swertia banzragczii and Swertia marginata (Gentianaceae) in Mongolia.

BACKGROUND: Swertia banzragczii and S. marginata are important medicinal species in Mongolia. However, their taxonomic positions and genetic backgrounds remain unknown. In this study, we explored the complete chloroplast genomes and DNA barcoding of these species and compared them with those of closely related species within the subgenus to determine their taxonomic positions and phylogenetic relationships. RESULT: The chloroplast genomes of S. banzragczii and S. marginata encoded 114 genes, including 80 protein-coding genes, 30 tRNA genes, and 4 rRNA genes. Among them, 16 genes contained a single intron, and 2 genes had two introns. Closely related species had a conserved genome structure and gene content. Only differences in genome length were noticed, which were caused by the expansion and contraction of the inverted repeat (IR) region and loss of exons in some genes. The trnH-GUG-psbA and trnD-GUC-trnY-GUA intergenic regions had high genetic diversity within Swertia plastomes. Overall, S. banzragczii and S. marginata are true species and belong to the subgenus Swertia. CONCLUSIONS: These results provide valuable genetic and morphological information on rare and subendemic Swertia species in Mongolia, which can be used for further advanced studies on the Swertia genus.

The complete chloroplast genome of Mussaenda pubescens and phylogenetic analysis.

The chloroplast (cp) genome sequence of Mussaenda pubescens, a promising resource that is used as a traditional medicine and drink, is important for understanding the phylogenetic relationships among the Mussaenda family and genetic improvement and reservation. This research represented the first comprehensive description of the morphological characteristics of M. pubescens, as well as an analysis of the complete cp genome and phylogenetic relationship. The results indicated a close relationship between M. pubescens and M. hirsutula based on the morphological characteristics of the flower and leaves. The cp was sequenced using the Illumina NovaSeq 6000 platform. The results indicated the cp genome of M. pubescens spanned a total length of 155,122 bp, including a pair of inverted repeats (IRA and IRB) with a length of 25,871 bp for each region, as well as a large single-copy (LSC) region and a small single-copy (SSC) region with lengths of 85,370 bp and 18,010 bp, respectively. The results of phylogenetic analyses demonstrated that species within the same genus displayed a tendency to group closely together. It was suggested that Antirhea, Cinchona, Mitragyna, Neolamarckia, and Uncaria might have experienced an early divergence. Furthermore, M. hirsutula showed a close genetic connection to M. pubescens, with the two species having partially overlapping distributions in China. This study presents crucial findings regarding the identification, evolution, and phylogenetic research on Mussaenda plants, specifically targeting M. pubescens.

The size diversity of the Pteridaceae family chloroplast genome is caused by overlong intergenic spacers.

BACKGROUND: While the size of chloroplast genomes (cpDNAs) is often influenced by the expansion and contraction of inverted repeat regions and the enrichment of repeats, it is the intergenic spacers (IGSs) that appear to play a pivotal role in determining the size of Pteridaceae cpDNAs. This provides an opportunity to delve into the evolution of chloroplast genomic structures of the Pteridaceae family. This study added five Pteridaceae species, comparing them with 36 published counterparts. RESULTS: Poor alignment in the non-coding regions of the Pteridaceae family was observed, and this was attributed to the widespread presence of overlong IGSs in Pteridaceae cpDNAs. These overlong IGSs were identified as a major factor influencing variations in cpDNA size. In comparison to non-expanded IGSs, overlong IGSs exhibited significantly higher GC content and were rich in repetitive sequences. Species divergence time estimations suggest that these overlong IGSs may have already existed during the early radiation of the Pteridaceae family. CONCLUSIONS: This study reveals new insights into the genetic variation, evolutionary history, and dynamic changes in the cpDNA structure of the Pteridaceae family, providing a fundamental resource for further exploring its evolutionary research.

Comparative Analysis of Sipeimine Content, Metabolome, and Chloroplast Genome in Cultivated and Wild Varieties of Fritillaria taipaiensis.

BACKGROUND: The wild variety Fritillaria taipaiensis E. B (EB) is known for its superior therapeutic effects, but its limited production cannot meet the demands. As a result, the cultivated variety F. taipaiensis P. Y. Li (PY) has been widely grown. In this study, we conducted a comprehensive analysis comparing EB and PY in terms of external features, Sipeimine content, metabolome, and chloroplast genome to differentiate these two varieties. RESULTS: Our research revealed that the petals and pods of EB are green, while those of PY have purple markings. The bulbs of EB contain significantly higher levels of Sipeimine compared to PY. Metabolomic analysis identified 56 differentially expressed metabolites (DMs), with 23 upregulated and 33 downregulated in EB bulbs. Particularly, 3-Hydroxycinnamic acid and Secoxyloganin may serve as distinctive differential metabolites. These DMs were associated with 17 KEGG pathways, including Pyrimidine metabolism, Alanine, Aspartate and Glutamate, and Galactose metabolism. Differences in the length of the chloroplast genome were primarily observed in the LSC region, with the largest variation in the trnH-GUC~psbA region. The placement of the trnH gene and the rps gene in proximity to the LSC/IRb boundary differs between EB and PY. CONCLUSION: The results of this study provide valuable insights for the introduction and comprehensive development of wild F. taipaiensis from a scientific perspective. This article is protected by copyright. All rights reserved.

The complete chloroplast genome assembly of Amorphophallus kiusianus makino 1913 (araceae) from Southern China.

The mountainous region of southern China has been characterized by its complicated environment and topography. Amorphophallus kiusianus Makino 1913 is a representative species of extreme habitat preference that resides mainly in this region. To help study the genetic differentiation mechanisms of A. kiusianus populations, we sequenced the first chloroplast genome of this species using next-generation sequencing. The chloroplast genome was 166,269 bp in length with an average GC content of 36% (GenBank accession number: PP072243). The lengths of the large single-copy region (LSC), small single-copy region (SSC), and two inverted repeats (IRs) were 90,701 bp, 14,802 bp, 31,383 bp, and 31,383 bp, respectively. One hundred and twenty-nine genes were annotated in the chloroplast genome, including 84 protein-coding genes, 8 rRNA genes, and 37 tRNA genes. The phylogenetic tree suggested a close relationship among A. kiusianus, A. yunnanensis, and A. coaetaneus. The chloroplast genome reported in this study provides valuable genomic resources for the future phylogeographic research of A. kiusianus.

Transcriptional and post-transcriptional regulation of chloroplast development by nuclear-localized XAP5 CIRCADIAN TIMEKEEPER.

Chlorophyll biosynthesis and breakdown, important cellular processes for photosynthesis, occur in the chloroplast. As a semi-autonomous organelle, chloroplast development is mainly regulated by nuclear-encoded chloroplast proteins and proteins encoded by itself. However, the knowledge of chloroplast development regulated by other organelles is limited. Here, we report that the nuclear-localized XAP5 CIRCADIAN TIMEKEEPER (XCT) is essential for chloroplast development in Arabidopsis. In this study, significantly decreased chlorophyll content phenotypes of cotyledons and subsequently emerging organs from shoot apical meristem were observed in xct-2. XCT is constitutively expressed in various tissues and localized in the nuclear with speckle patterns. RNA-seq analysis identified 207 differently spliced genes and 1511 differently expressed genes, in which chloroplast development-, chlorophyll metabolism- and photosynthesis-related genes were enriched. Further biochemical assays suggested that XCT was co-purified with the well-known splicing factors and transcription machinery, suggesting dual functions of XCT in gene transcription and splicing. Interestingly, we also found that the chlorophyll contents in xct-2 significantly decreased under high temperature and high light condition, indicating XCT integrates temperature and light signals to fine-tune the chlorophyll metabolism in Arabidopsis. Therefore, our results provide new insights into chloroplast development regulation by XCT, a nuclear-localized protein, at the transcriptional and post-transcriptional level.

Hybridization and reticulate evolution in Diphasiastrum (flat-branched clubmosses, Lycopodiaceae) - New data from the island of Taiwan and Vietnam.

In the species groups related to Diphasiastrum multispicatum and D. veitchii, hybridization was investigated in samples from northern and southern Vietnam and the island of Taiwan, including available herbarium specimens from southeast Asia. The accessions were analyzed using flow cytometry (living material only), Sanger sequencing and multiplexed inter-simple sequence repeat genotyping by sequencing. We detected two cases of ancient hybridization involving different combinations of parental species; both led via subsequent duplication to tetraploid taxa. A cross D. multispicatum × D. veitchii from Malaysia represents D. wightianum, a tetraploid taxon according to reported DNA content measurements of dried material (genome formulas MM, VV and MMVV, respectively). The second case involves D. veitchii and an unknown diploid parent (genome formula XX). Three hybridogenous taxa (genome formulas VVX, VVXX, VVVX) were discernable by a combination of flow cytometry and molecular data. Taxon I (VVX, three clones found on Taiwan island) is apparently triploid. Taxon II represents another genetically diverse and sexual tetraploid species (VVXX) and can be assigned to D. yueshanense, described from Taiwan island but occurring as well in mainland China and Vietnam. Taxon III is as well most likely tetraploid (VVVX) and represented by at least one, more likely two, clones from Taiwan island. Taxa I and III are presumably asexual and new to science. Two independently inherited nuclear markers recombine only within, not between these hybrids, pointing towards reproductive isolation. We present an evolutionary scheme which explains the origin of the hybrids and the evolution of new and fully sexual species by hybridization and subsequent allopolyploidization in flat-branched clubmosses.

A new combination and synonym in Bupleurum (Apiaceae, Apioideae), based on morphological, molecular and cytological evidence.

Specimen examinations and field observations revealed that Bupleurumsmithiivar.parvifolium was distinctly different from B.smithiivar.smithii in umbel, leaf, and fruit morphology, but was very similar to B.commelynoideumvar.flaviflorum. Based on these morphological evidences, the present study re-examined the taxonomic status of these taxa through morphological, cytological, and phylogenetic analyses. The results showed distinguishable features in the width of middle leaves and bracteoles of B.smithiivar.parvifolium compared to B.smithiivar.smithii. Morphological variation between B.smithiivar.parvifolium and B.commelynoideumvar.flaviflorum was continuous and overlapping. Notably, the chromosome number of B.smithiivar.parvifolium was 2n = 14 (x = 7), consistent with B.commelynoideumvar.flaviflorum, whereas B.smithiivar.smithii was 2n = 64 (x = 8). Additionally, phylogenetic analyses revealed B.commelynoideumvar.flaviflorum nested within B.smithiivar.parvifolium, and that both were distant from the B.smithiivar.smithii and B.commelynoideumvar.commelynoideum. Based on the evidence above, the differences between B.smithiivar.parvifolium and B.smithiivar.smithii extend beyond the level of intraspecific variation, and B.commelynoideumvar.flaviflorum is considered to be identical with B.smithiivar.parvifolium. Hence. A new combination and status, B.parvifolium (Shan & Y.Li) Q.R.Liu & L.H.Wang, comb. et stat. nov., is proposed. Furthermore, B.commelynoideumvar.flaviflorum should be treated as a synonym of B.parvifolium.

S2P2-the chloroplast-located intramembrane protease and its impact on the stoichiometry and functioning of the photosynthetic apparatus of A. thaliana.

S2P2 is a nuclear-encoded protease, potentially located in chloroplasts, which belongs to the zinc-containing, intramembrane, site-2 protease (S2P) family. In A. thaliana cells, most of the S2P proteases are located within the chloroplasts, where they play an important role in the development of chloroplasts, maintaining proper stoichiometric relations between polypeptides building photosynthetic complexes and influencing the sensitivity of plants to photoinhibitory conditions. Among the known chloroplast S2P proteases, S2P2 protease is one of the least known. Its exact location within the chloroplast is not known, nor is anything known about its possible physiological functions. Therefore, we decided to investigate an intra-chloroplast localization and the possible physiological role of S2P2. To study the intra-chloroplast localization of S2P2, we used specific anti-S2P2 antibodies and highly purified chloroplast fractions containing envelope, stroma, and thylakoid proteins. To study the physiological role of the protease, we used two lines of insertion mutants lacking the S2P2 protease protein. Here, we present results demonstrating the thylakoid localization of S2P2. Moreover, we present experimental evidence indicating that the lack of S2P2 in A. thaliana chloroplasts leads to a significant decrease in the level of photosystem I and photosystem II core proteins: PsaB, PsbA, PsbD, and PsbC, as well as polypeptides building both the main light-harvesting antenna (LHC II), Lhcb1 and Lhcb2, as well as Lhcb4 and Lhcb5 polypeptides, constituting elements of the minor, peripheral antenna system. These changes are associated with a decrease in the number of PS II-LHC II supercomplexes. The consequence of these disorders is a greater sensitivity of s2p2 mutants to photoinhibition. The obtained results clearly indicate that the S2P2 protease is another thylakoid protein that plays an important role in the proper functioning of A. thaliana chloroplasts, especially in high-light-intensity conditions.

The complete chloroplast genome of Hemiboea pterocaulis (Gesneriaceae) exclusively distributed in Guilin, Guangxi, China.

Hemiboea pterocaulis is a unique species only found in Guilin, Guangxi, China. In this study, we sequenced and assembled the complete chloroplast genome of H. pterocaulis and revealed its phylogenetic relationship with other Hemiboea species. The chloroplast genome sequence of H. pterocaulis is 153,159 bp in length and comprises a large single-copy (LSC) region of 84,178 bp, a small single-copy (SSC) region of 18,087 bp, and a pair of inverted repeat (IR) regions, each with a length of 25,447 bp. It has a total GC content of 37.6% and encodes 132 genes, including 87 protein-coding genes, 37 tRNA genes, and eight rRNA genes. The phylogenetic relationships based on the complete chloroplast genome sequences of Hemiboea taxa indicate that H. pterocaulis is most closely related to H. suiyangensis, indicating that H. pterocaulis is an independent species and is separated from the H. subcapitata complex. These results provide valuable insights into the phylogeny, species divergence, and delimitation of the Hemiboea genus.

The complete chloroplast genomes of three Alismataceae species, including the medicinally important Alisma orientale.

Alismataceae is one of the early diverged families of monocotyledonous plants. We report the complete chloroplast genomes of three Alisma species, including Alisma orientale (Sam.) Juzep. 1934, A. subcordatum Raf. 1908, and A. triviale Pursh 1813, of which A. orientale is a traditional Chinese medical plant used widely to treat diuretics, diabetes, hepatitis, and inflammation. We sequenced the complete chloroplast genomes with the Illumina Nova-Seq 6000 platform using herbarium collections. The chloroplast genomes of A. orientale, A. subcordatum and A. triviale are 159,861 bp, 160,180 bp, and 159,727 bp in length, respectively. The three chloroplast genomes each contain 113 genes, including four rRNAs, 30 tRNAs genes, and 79 protein-coding genes, and the average GC content is 36.0%. Based on the whole chloroplast genomes of 19 species of Alismataceae and the close allies, the medicinally important A. orientale was found to be closely related to another medicinal plant Alisma plantago-aquatica L. 1753 in the phylogenetic analysis. The genus Alisma was supported to be monophyletic.