Types Of Chloroplasts Research Articles

A description of Aliichlorella ignota gen. et sp. nov. and a comparison of the efficiency of species delimitation methods in the Chlorella‐clade (Trebouxiophyceae, Chlorophyta)

AbstractThe present study reports a new representative of Chlorella‐clade that was newly isolated from the Lake Vos'merka (Samara region, Russian Federation). 18S–ITS1–5.8S–ITS2 sequence analyses indicated that the studied strain ACSSI 368 and related Chlorella chlorelloides, Chlorella pulchelloides, formed an separate cluster in the Chlorella‐clade, unrelated to the holotype of the genus Chlorella – Chlorella vulgaris. The independent place of the genus was also confirmed by genetic distances. The individual species status of the studied strain ACSSI 368, compared with the sister C. chlorelloides, was confirmed by morphological differences (cell number per colony, type of chloroplast, number of autospores), genetic distances of the interspecific level by 18S–ITS1–5.8S–ITS2 fragment, alone by internal transcribed spacer 1 (ITS1) and internal transcribed spacer 2 (ITS2) sequences, one complementary base change in ITS1, and the results of species delimitation using five methods. A description of studied strain ACSSI 368 was provided as an authentic strain of the type species Aliichlorella ignota. Currently, the new genus Aliichlorella also includes Aliichlorella chlorelloides comb. nov. and Aliichlorella pulchelloides comb. nov. In general, six different delimitation algorithms were used in the present study. The ASAP (i.e. assemble species by automatic partitioning) and LocMin (i.e. ‘local minimum’ function) algorithms showed synchronous results, but their accuracy with respect to closely related species was somewhat lower. The mlPTP algorithm simultaneously aimed to combine closely related species in one and at the same time divide slightly distinguishing strains within a species into several molecular operational taxonomic units. The bPTP algorithm separated excessively Chlorella‐clade representatives into individual species. The generalized mixed Yule coalescent (GMYC) algorithm results were consistent the most with the modern understanding of the Chlorella‐clade taxonomy. However, the same method is one of the most time‐consuming because, for its implementation, it is necessary to carry out long preparatory work. The KoT results were less accurate than the GMYC results, although this is less time‐consuming because it does not require the preliminary construction of ultrametric trees.

Comparative Phylogenetic Analysis of Ancient Korean Tea "Hadong Cheon-Nyeon Cha (Camellia sinensis var. sinensis)" Using Complete Chloroplast Genome Sequences.

Wild teas are valuable genetic resources for studying evolution and breeding. Here, we report the complete chloroplast genome of the ancient Korean tea 'Hadong Cheon-nyeon Cha' (C. sinensis var. sinensis), which is known as the oldest tea tree in Korea. This study determined seven Camellia sinensis var. sinenesis, including Hadong Cheon-nyeon Cha (HCNC) chloroplast genome sequences, using Illumina sequencing technology via de novo assembly. The chloroplast genome sizes ranged from 157,019 to 157,114 bp and were organized into quadripartite regions with the typical chloroplast genomes. Further, differences in SNPs and InDels were detected across the seven chloroplast genomes through variance analysis. Principal component and phylogenetic analysis suggested that regional constraints, rather than functional constraints, strongly affected the sequence evolution of the cp genomes in this study. These genomic resources provide evolutionary insight into Korean tea plant cultivars and lay the foundation for a better understanding of the ancient Korean tea plant HCNC.

Evolution and Expression Patterns of the Fructose 1,6-Bisphosptase Gene Family in a Miracle Tree (Neolamarckia cadamba).

Neolamarckia cadamba (N. cadamba) is a fast-growing tree species with tremendous economic and ecological value; the study of the key genes regulating photosynthesis and sugar accumulation is very important for the breeding of N. cadamba. Fructose 1,6-bisphosptase (FBP) gene has been found to play a key role in plant photosynthesis, sugar accumulation and other growth processes. However, no systemic analysis of FBPs has been reported in N. cadamba. A total of six FBP genes were identifed and cloned based on the N. cadamba genome, and these FBP genes were sorted into four groups. The characteristics of the NcFBP gene family were analyzed such as phylogenetic relationships, gene structures, conserved motifs, and expression patterns. A cis-acting element related to circadian control was first found in the promoter region of FBP gene. Phylogenetic and quantitative real-time PCR analyses showed that NcFBP5 and NcFBP6 may be chloroplast type 1 FBP and cytoplasmic FBP, respectively. FBP proteins from N. cadamba and 22 other plant species were used for phylogenetic analyses, indicating that FBP family may have expanded during the evolution of algae to mosses and differentiated cpFBPase1 proteins in mosses. This work analyzes the internal relationship between the evolution and expression of the six NcFBPs, providing a scientific basis for the evolutionary pattern of plant FBPs, and promoting the functional studies of FBP genes.

Dissipation of the proton electrochemical gradient in chloroplasts promotes the oxidation of ATP synthase by thioredoxin-like proteins

Chloroplast FoF1-ATP synthase (CFoCF1) uses an electrochemical gradient of protons across the thylakoid membrane (ΔμH+) as an energy source in the ATP synthesis reaction. CFoCF1 activity is regulated by the redox state of a Cys pair on its central axis, that is, the γ subunit (CF1-γ). When the ΔμH+ is formed by the photosynthetic electron transfer chain under light conditions, CF1-γ is reduced by thioredoxin (Trx), and the entire CFoCF1 enzyme is activated. The redox regulation of CFoCF1 is a key mechanism underlying the control of ATP synthesis under light conditions. In contrast, the oxidative deactivation process involving CFoCF1 has not been clarified. In the present study, we analyzed the oxidation of CF1-γ by two physiological oxidants in the chloroplast, namely the proteins Trx-like 2 and atypical Cys-His-rich Trx. Using the thylakoid membrane containing the reduced form of CFoCF1, we were able to assess the CF1-γ oxidation ability of these Trx-like proteins. Our kinetic analysis indicated that these proteins oxidized CF1-γ with a higher efficiency than that achieved by a chemical oxidant and typical chloroplast Trxs. Additionally, the CF1-γ oxidation rate due to Trx-like proteins and the affinity between them were changed markedly when ΔμH+ formation across the thylakoid membrane was manipulated artificially. Collectively, these results indicate that the formation status of the ΔμH+ controls the redox regulation of CFoCF1 to prevent energetic disadvantages in plants.

Light-Dependent Reactions of Photosynthesis in Mesophyll and Bundle Sheath Chloroplasts of C4 Plant Maize. How Our Views Have Changed in Recent Years

Abstract Plants experience a range of light intensities and qualities in their environment. Leaves are subjected to spatial and temporal gradients in incident light, which has major consequences in the photosynthetic carbon assimilation. Plants acclimate to light by developing a range of mechanisms, from adjustments in leaf morphology to changes in the photosynthetic apparatus stoichiometry. In C4 plants, light intensity is a major limiting factor for photosynthesis at optimum temperatures. Under limiting light, it is not clear if all of factors (e.g., temperature, mineral nutrition, water supply) are co-limiting or if there is one primary limitation. Differences in light quality and intensity have a profound impact on C4 photosynthesis, where pathways require metabolic coordination of the mesophyll and bundle sheath cycles. Changes in the linear versus cyclic electron flux in maize (NADP-malic enzyme C4 subtype) in the mesophyll and bundle sheath chloroplasts in response to light may lead to an imbalance in the coordination of the C3 and C4 pathways. Additionally, the rearrangement of the thylakoid complexes of both types of chloroplasts in maize optimizes the light energy distribution between the mesophyll and bundle sheath cells and may also participate in energy dissipation. This review aims to highlight the changes in the understanding of the functions of photosystem II in maize bundle sheath chloroplasts and the role of super and megacomplexes in the thylakoids.

The complete plastid genome of Terminalia myriocarpa Vaniot Huerck et Muell.-Arg (Combretaceae), a tropical rainforest indicator species in Southern China

Terminalia myriocarpa Vaniot Huerck et Muell.-Arg is a tropical rainforest indicator species in Southern China. The chloroplast genome of T. myriocarpa was analyzed by high-throughput sequence technology, and its genetic relationship to related species was discussed. The chloroplast genome is 159,854 bp in length, with a total GC content of 37%. It has a typical chloroplast tetrad structure, including 88,015 bp of large single copy (LSC), 18,814 bp of small single copy (SSC), and 26,319 bp of inverted repeats (IR). A total of 130 genes were annotated, including 85 protein-coding genes, 8 rRNA genes, and 37 tRNA genes. Phylogenetic analysis indicated T. myriocarpa was closely related to Terminalia phillyreifolia.

Species delimitation and microalgal cryptic diversity analysis of the genus Micractinium (Chlorophyta).

In this article, the system of the green microalgal genus Micractinium, based on morphological, physiological, ecological and molecular data, is considered. The main diagnostic species characteristics and the taxonomic placement of some taxa are also discussed. Phylogenetic analysis showed that the genus Micractinium is characterized by high cryptic diversity. The algorithms used for species delimitation had different results on the number of potentially species-level clusters allocated. The ABGD method was less “sensitive”. The tree-based approaches GMYC and PTP showed a more feasible taxonomy of the genus Micractinium, being an effective additional tool for distinguishing species. The clustering obtained by the latter two methods is in good congruence with morphological (cell size and shape, ability to form colonies, production of bristles, chloroplast type), physiological (vitamin requirements, reaction to high and low temperatures), molecular (presence of introns, level of genetic differences, presence of CBCs or special features of the secondary structure in ITS1 and ITS2) and ecological characteristics (habitat). The polyphyly of the holotype of the genus M. pusillum as well as M. belenophorum is shown. The intron was effective as an additional tool for distinguishing species, and the results of the intron analysis should be taken into account together with other characteristics. The CBC approach, based on the search for compensatory base changes in conservative ITS2 regions, was successful only for distinguishing cryptic species from “true” members of M. pusillum. Therefore, to distinguish species, it is more effective to take into account all the CBC in ITS1 and ITS2 and analyze characteristic structural differences (molecular signatures) in the secondary structure of internal transcribed spacers. The genetic distances analysis of 18S–ITS1–5.8S–ITS2 nucleotide sequences showed that intraspecific differences in the genus ranged from 0 to 0.5 % and interspecific differences, from 0.6 to 4.7 %. Due to the polyphasic approach, it was possible to characterize 29 clusters and phylogenetic lines at the species level within the genus Micractinium and to make assumptions about the species.

Evaluation of the validity of large-scale serial sectioning TEM for three-dimensional reconstruction of rice mesophyll cells and chloroplasts.

Serial sectioning transmission electron microscopy (ssTEM) is a classical method of 3D reconstruction using serial sections obtained with an ultramicrotome. However, producing a long ribbon with homogeneity is difficult. Here, ultramicrotome movement was suspended after producing a ribbon of 15-30 serial sections (cutting intervals, 100nm), and then, the ribbon was mounted on an individual one-slot grid. However, as this ssTEM method may include influencing factors such as incorrect intervals of section thickness and distortion of sections, which is produced by cutting sections using a diamond knife and beam interaction under TEM observation, qualitative and quantitative data on rice mesophyll cells and chloroplasts were compared with those obtained from a focused ion beam scanning electron microscopy (FIB-SEM) (cutting intervals, 50nm). No structural distortion in 3D models was observed. In addition, no significant differences in the volume and surface area were observed between the two methods. The surface to volume ratio was significantly affected by the increase in section thickness, but not the difference of methodologies. Our method was useful for observing large volumes of plant cells and organelles, leading to the identification of various sizes and types of chloroplasts. The formation of a chloroplast pocket, which is a structure surrounding other intracellular compartments, was confirmed in rice leaves grown under moderate growth conditions using the ssTEM method. As only four out of 90 chloroplasts formed pocket structures, the formation was considered to be rare under the applied moderate growth conditions.

A new genus of soil green microalgae Edaphochloris gen. nov. (Chlorellaceae, Trebouxiophyceae)

The problem of studying the species diversity of small single-celled green coccoid microalgae (Chlorophyta) is still relevant, since their simple and uniform cellular morphology makes it extremely difficult to correctly identify them. It is now generally accepted that the best approach for creating a new, more natural classification of “little green balls” is an approach that combines morphological, ecological, physiological and molecular phylogenetic methods. Strains ACSSI 104 and ACSSI 144 were isolated from solonetz and chestnut soil (Volgograd region, Russia). Their cells have a typical Nannochloris-like morphology: single spherical or subspherical cells, chloroplast single, parietal, cup-shaped, without pyrenoid, but with starch grains in it. Old cells accumulate numerous oil droplets in cytoplasm. Reproduction by 2−4 autospores. Autospores of both strains are equal size and exhibit liberation by rupture of sporangium cell wall. Zoospores and sexual reproduction not observed. Both strains are part of independent cluster closely related to genera Marvania, Pumiliosphaera, Nannochloris and Gloeotila. A comparative analysis of morphological (cell size, chloroplast type) and ultrastructural characteristics (structure of cell wall and lamellar system), features of reproduction (asexual reproduction by autospores only) and habitat (soil) with other members of the Nannochloris-clade, as well as results of analysis of 18S rRNA gene and ITS2 secondary structure of the studied strains, allowed us to propose a new genus – Edaphochloris with the type species – E. andreyevae. The report was prepared based on the materials of the V All-Russian Scientific Conference with international participation "Algae: problems of systematics, ecology and use in monitoring", 2021.

The disassembly of lipid droplets in Chlamydomonas.

Lipid droplets (LDs) are ubiquitous and specialized organelles in eukaryotic cells. Consisting of a triacylglycerol core surrounded by a monolayer of membrane lipids, LDs are decorated with proteins and have myriad functions, from carbon/energy storage to membrane lipid remodeling and signal transduction. The biogenesis and turnover of LDs are therefore tightly coordinated with cellular metabolic needs in a fluctuating environment. Lipid droplet turnover requires remodeling of the protein coat, lipolysis, autophagy and fatty acid β-oxidation. Several key components of these processes have been identified in Chlamydomonas (Chlamydomonas reinhardtii), including the major lipid droplet protein, a CXC-domain containing regulatory protein, the phosphatidylethanolamine-binding DTH1 (DELAYED IN TAG HYDROLYSIS1), two lipases and two enzymes involved in fatty acid β-oxidation. Here, we review LD turnover and discuss its physiological significance in Chlamydomonas, a major model green microalga in research on algal oil.

Incidence of Asiatic Citrus Canker on Trifoliate Orange and Its Hybrid Accessions in a Florida Field Planting

Asiatic citrus canker (ACC) foliar lesions were evaluated on progenies of 84 seed-source genotypes (“parent genotypes”) from the Citrus Variety Collection (CVC) of the University of California at Riverside (UCR) of Citrus trifoliata and hybrids between C. trifoliata and other Citrus species and hybrids. Trees were planted Aug. 2013 in a completely randomized design at the Fort Pierce U.S. Department of Agriculture (USDA) grove. Plants were assessed visually Aug. 2017, Sept. 2019, and Sept. 2020 for distinctive ACC lesion incidence and severity. Progeny were compared by parent genotypes using nonparametric analysis. Incidence of ACC [percentage of leaves displaying symptoms, verified by quantitative polymerase chain reaction (qPCR) to be associated with Xanthomonas citri pv. citri] across parent genotypes ranged from 8% to 80% (mean, 49%) of leaves affected in 2017, from 4% to 58% (mean, 29%) in 2019, and 8% to 46% (mean, 25%) in 2020. In 2017, of 49 C. trifoliata parent genotypes, only four separated from the two highest ACC-incidence statistical categories [Citrus Research Center (CRC) 3345, 3484, 3888, and 4017]. whereas 29 of the 35 C. trifoliata hybrids displayed lower ACC incidence, which separated from the two highest statistical categories. In 2019, of the C. trifoliata, only six separated from the highest ACC-incidence statistical category (CRC 3330, 3484, 3547, 3549, 3876, and 3888), whereas all 35 C. trifoliata hybrids displayed lower ACC incidence and separated from the highest statistical category, and 26 hybrids separated from 18 of the C. trifoliata. In 2020, only three C. trifoliata separated from the highest ACC-incidence statistical category (CRC 2861, 3549, and 3888) and 20 hybrids separated from 18 of the C. trifoliata. By parent genotype, ACC incidence correlated substantially between each pair of the 3 years, with r2 values of 0.39, 0.57, and 0.65. Of 34 hybrids validated, similar numbers had C. trifoliata, grapefruit (C. ×aurantium var. racemosa), and sweet orange (C. ×aurantium var. sinensis) chloroplasts. Chloroplast type affected ACC incidence and severity, but not in a consistent manner. Near-isogenic groups within C. trifoliata, as determined by DNA markers, were associated with some statistically different ACC sensitivity. Overall, hybrids of C. trifoliata with other citrus types displayed markedly reduced ACC sensitivity compared with C. trifoliata, indicating that this trait is readily overcome through breeding.

The highly conserved rps12 gene in ferns provides strong evidence for decreased substitution rates in the inverted repeat region

The typical chloroplast genome consists of two inverted repeat (IR) and two single-copy (SC) regions. Each region has its own pattern of molecular evolution. Many studies have shown that the IR region has a low substitution rate. The plastid rps12 gene encodes ribosomal protein small subunit 12, which is composed of 5′-rps12 (exon 1) and 3′-rps12 (exon 2–3); 3′-rps12 is near the IR region and enters or leaves the IR region as it expands and contracts, enabling study of the variation in its substitution rate. We analyzed the evolutionary rate and adaptive evolution of the rps12 genes of 118 ferns and 2 lycophytes in a phylogenetic context using the maximum likelihood method. We found that the substitution rate of exon 2–3 was significantly lower in the IR region than in the LSC (1–11 times higher in the LSC), and also lower than that of exon 1 in the LSC region (1.9–6.7 times higher for exon 1). In addition, there was more GC content at the third codon position, and the rps12 gene encoded 123 amino acids, with 107 negative selection sites and 4 positive selection sites. These results prove that the substitution rate decreases after the sequence fragments enter the IR region and demonstrate the highly conserved nature of the rps12 gene.

A Carbon Fixation Enhanced Chlamydomonas reinhardtii Strain for Achieving the Double-Win Between Growth and Biofuel Production Under Non-stressed Conditions.

The stressed cultivations are widely used in microalgae R&D for the biofuel production with the repress on growth to a certain degree, which limits the overall productivity. The balance between the growth and energy storage compounds accumulation is a target needing the combination of both strain selection or construction and culture optimization. Here, an engineered strain of Chlamydomonas reinhardtii, in which the chloroplast type glyceraldehyde-3-phosphate dehydrogenase (cGAPDH) was overexpressed and named as P3-GAPDH, was cultured on the Algal Station platform. Compared with wild type (WT), C. reinhardtii CC137c, in Tris-acetate-phosphate (TAP) medium, the highest density of WT and P3-GAPDH were 1.23 ± 0.13 and 1.74 ± 0.09 g L–1 within 96 h, and the maximum biomass productivity was 24.30 ± 1.65 and 28.54 ± 1.43 mg L–1 h–1, respectively. In terms of the energy storage compounds, both carbohydrate and fatty acids content doubled in P3-GAPDH, from 0.13 ± 0.02 to 0.26 ± 0.04 g L–1 for carbohydrate and from 0.08 ± 0.01 to 0.16 ± 0.01 g L–1 for fatty acids, among which poly unsaturated fatty acids increased by 65.8%. Together with the continuous monitor of the chlorophyll fluorescence dynamics parameters Fv/Fm and Fv’/Fm’ and pH of culture, enhanced Calvin cycle by overexpressed cGAPDH promoted the carbon conversion and subsequent energy storage compounds accumulation. C. reinhardtii P3-GAPDH strain showed the potential as a good chassis with high carbon conversion ability.

Pigment content analysis in two HAB forming dinoflagellate species during the growth period

Dinoflagellates form a large group of microalgae that have different pigments and the pigment content can vary depending on environmental conditions such as temperature, salinity, and their growth phase. They have the potential to cause red tides in coastal waters, so it is important to identify their pigments. In this study, two bloom forming dinoflagellate species, Scrippsiella trochoidea and Gyrodinium instriatum from the Oman Sea, were studied for their pigment content by HPLC every 5 days over a 30-day growth period. In both species, 10 pigment types were identified: unknown carotenoids, chlorophyll (chl) c2, peridinin, peridinin-like, diadinochrome, diadinoxanthin, dinoxanthin, diatoxanthin, chl a, and β,β-carotene. Although both species have the same pigment types, they vary in concentration in different days of growth. The highest cell density in S. trochoidea species was on day 15 of the growth period and the predominant pigments were chl c2, diadinoxanthin, and chl a. Peridinin, peridinin-like, diadinochrome, and β,β-carotene were predominant pigments on day 10, before the cell reached its maximum density. In G. instriatum, the highest cell density during the growth period was in day 10. The highest levels of unknown carotenoids, chl c2, diadinoxanthin, dinoxanthin, peridinin, peridinin-like, diadinochrome, and β,β-carotene pigments were measured on day 25 of growth. The type of chloroplast in both species was the peridinin type. In interpreting the pigment concentration and type, the age of the species should be considered.

The ten amino acids of the oxygen-evolving enhancer of tobacco is sufficient as the peptide residues for protein transport to the chloroplast thylakoid

Key messageThe thylakoid transit peptide of tobacco oxygen-evolving enhancer protein contains a minimal ten amino acid sequences for thylakoid lumen transports. This ten amino acids do not contain twin-arginine, which is required for typical chloroplast lumen translocation.Chloroplasts are intracellular organelles responsible for photosynthesis to produce organic carbon for all organisms. Numerous proteins must be transported from the cytosol to chloroplasts to support photosynthesis. This transport is facilitated by chloroplast transit peptides (TPs). Four chloroplast thylakoid lumen TPs were isolated from Nicotiana tabacum and were functionally analyzed as thylakoid lumen TPs. Typical chloroplast stroma-transit peptides and thylakoid lumen transit peptides (tTPs) are found in N. tabacum transit peptides (NtTPs) and the functions of these peptides are confirmed with TP–GFP fusion proteins under fluorescence microscopy and chloroplast fractionation, followed by Western blot analysis. During the functional analysis of tTPs, we uncovered the minimum 10 amino acid sequence is sufficient for thylakoid lumen transport. These ten amino acids can efficiently translocate GFP protein, even if they do not contain the twin-arginine residues required for the twin-arginine translocation (Tat) pathway, which is a typical thylakoid lumen transport. Further, thylakoid lumen transporting processes through the Tat pathway was examined by analyzing tTP sequence functions and we demonstrate that the importance of hydrophobic core for the tTP cleavage and target protein translocation.

Two divergent chloroplast genome sequence clades captured in the domesticated rice gene pool may have significance for rice production

BackgroundThe whole chloroplast genomes of 3018 rice genotypes were assembled from available sequence data by alignment with a reference rice chloroplast genome sequence, providing high quality chloroplast genomes for analysis of diversity on a much larger scale than in any previous plant study.ResultsUpdated annotation of the chloroplast genome identified 13 more tRNA genes and 30 more introns and defined the function of more of the genes. Domesticated rice had chloroplast genomes that were distinct from those in wild relatives. Analysis confirms an Australian chloroplast clade as a sister to the domesticated clade. All domesticated rice genotypes could be assigned to one of two main clades suggesting the domestication of two distinct maternal genome clades that diverged long before domestication. These clades were very distinct having 4 polymorphisms between all 1486 accession in clade A and all 1532 accessions in clade B. These would result in expression of 3 proteins with altered amino acid sequences and a tRNA with an altered sequence and may be associated with adaptive evolution of the two chloroplast types. Diversity within these pools may have been captured during domestication with subclades enriched in specific groups such as basmati, tropical japonica and temperate japonica. However the phylogenies of the chloroplast and nuclear genomes differed possibly due to modern rice breeding and reticulate evolution prior to domestication. Indica and aus genotypes were common in both chloroplast clades while japonica genotypes were more likely to be found in the same clade (cladeB).ConclusionsThe different evolutionary paths of the cytoplasmic and nuclear genomes of rice have resulted in the presence of apparently functional chloroplast genome diversity and the implications for rice crop performance require further investigation.

Response of anatomy and CO2-concentrating mechanisms to variable CO2 in linear juvenile leaves of heterophyllous Ottelia alismoides: Comparisons with other leaf types

Ottelia alismoides (Hydrocharitaceae) is a heterophyllous freshwater macrophyte which shows heteroblastic heterophylly during plant development, and differs in carbon dioxide-concentrating mechanisms (CCMs) at different stage. This study investigated the anatomy and CCMs in the first stage of leaf during O. alismoides development, linear juvenile leaves. It comprised three layers of cell and enriched air spaces, but not significantly affected by CO2 concentration ([CO2]), while leaf thickness and chloroplast ultrastructure were significantly affected by [CO2]. The linear juvenile leaves could perform C4 photosynthesis at low [CO2]; the two types of chloroplasts distributed in epidermal and mesophyll cells respectively, with different shape and starch content, might provide the structural basis for C4 operation. The pH-drift data showed that the linear juvenile leaves could use HCO3− regardless of [CO2]. Whereas, CAM and C4 operation could only be induced at low [CO2]. When compared the CCMs among all the heteromorphic leaves in O. alismoides, it is shown that CCMs in the O. alismoides heteromorphic leaves become more diversified during the plants development: HCO3− use was present in all leaf-types regardless of the [CO2]; CAM and C4 were only induced at low [CO2] and became more efficient in mature leaves. The anatomy was also regulated to adapt to the functions of CCMs, and ultimately, the ovate mature leaves can operate C4 constitutively.

Electron Microscopy Views of Dimorphic Chloroplasts in C4 Plants.

C4 plants enhance photosynthesis efficiency by concentrating CO2 to the site of Rubisco action. Chloroplasts in C4 plants exhibit structural dimorphism because thylakoid architectures vary depending on energy requirements. Advances in electron microscopy imaging capacity and sample preparation technologies allowed characterization of thylakoid structures and their macromolecular arrangements with unprecedented precision mostly in C3 plants. The thylakoid is assembled during chloroplast biogenesis through collaboration between the plastid and nuclear genomes. Recently, the membrane dynamics involved in the assembly process has been investigated with 3D electron microscopy, and molecular factors required for thylakoid construction have been characterized. The two classes of chloroplasts in C4 plants arise from common precursors, but little is known about how a single type of chloroplasts grow, divide, and differentiate to mature into distinct chloroplasts. Here, we outline the thylakoid structure and its assembly processes in C3 plants to discuss ultrastructural analyses of dimorphic chloroplast biogenesis in C4 plant species. Future directions for electron microscopy research of C4 photosynthetic systems are also proposed.

Cytoplasmic diversity of potato relatives preserved at Plant Breeding and Acclimatization Institute in Poland

Among different types of potato cytoplasmic genomes, some are associated with male sterility or affect agronomic traits. The goal of this study was to analyze types of chloroplast and mitochondrial genomes of selected potato relatives originating from collection of the Institute of Plant Industry, Saint Petersburg, Russia, and preserved in Poland. Using chloroplast and mitochondrial markers the cytoplasm types were determined for 401 genotypes belonging to 43 seed accessions of 28 Solanum species. Among characterized genotypes, 201 (50.1%), 156 (38.9%) and 44 (11%) had cytoplasm types W, D, M, respectively. No accessions with the T, P or A cytoplasm were found. Within cytoplasm W, genotypes with the subtypes: W/α and W/β were identified, but not with W/γ. In S. famatinae, we detected unusual product of the T marker with 65 bp insertion earlier seen exclusively in S. vernei. Among the genotypes of S. leptophyes, two profiles of the ALM_4/ALM_5 marker were observed. S. famatinae and S. vernei come from Argentina, provinces Catamarca and Tucumán. Possibly the insertion in marker T occurred independently in two species, or the accessions were misidentified. Segregation of the ALM_4/ALM_5 marker within S. leptophyes indicates that potato seed accessions are heterogeneous not only due to nuclear DNA polymorphisms but have diversified cytoplasm, too. Our findings are important for exploitation of the tested material in potato breeding. Male-fertile cytoplasm types give a chance of avoiding fertility problems and widening the range of crosses in future generations of breeding materials.

Invasion, isolation and evolution shape population genetic structure in Campanula rotundifolia.

The distribution and genetic structure of most plant species in Britain and Ireland bear the imprint of the last ice age. These patterns were largely shaped by random processes during recolonization but, in angiosperms, whole-genome duplication may also have been important. We investigate the distribution of cytotypes of Campanula rotundifolia, considering DNA variation, postglacial colonization, environmental partitioning and reproductive barriers. Cytotypes and genome size variation from across the species’ range were determined by flow cytometry and genetic variation was assessed using cpDNA markers. A common garden study examined growth and flowering phenology of tetraploid, pentaploid and hexaploid cytotypes and simulated a contact zone for investigation of reproductive barriers. Irish populations were entirely hexaploid. In Britain, hexaploids occurred mostly in western coastal populations which were allopatric with tetraploids, and in occasional sympatric inland populations. Chloroplast markers resolved distinct genetic groups, related to cytotype and geographically segregated; allopatric hexaploids were distinct from tetraploids, whereas sympatric hexaploids were not. Genome downsizing occurred between cytotypes. Progeny of open-pollinated clones from the contact zone showed that maternal tetraploids rarely produced progeny of other cytotypes, whereas the progeny of maternal hexaploids varied, with frequent pentaploids and aneuploids. The presence of distinctive hexaploid chloroplast types in Ireland, Scottish islands and western mainland Britain indicates that its establishment preceded separation of these land masses by sea-level rise c. 16 000 years BP. This group did not originate from British tetraploids and probably diverged before postglacial invasion from mainland Europe. The combination of cytotype, molecular, contact zone and common garden data shows an overall pattern reflecting postglacial colonization events, now maintained by geographic separation, together with more recent occasional local in situ polyploidisation. Reproductive barriers favour the persistence of the tetraploid to the detriment of the hexaploid.