Sacoglossan sea slugs are able to steal chloroplasts from their algal prey and acquire photosynthetic capacity (termed kleptoplasty). These ‘stolen’ plastids provide sea slugs with a long-term supply of organic carbon and energy. This augmented nutrient supply brings many benefits in terms of survival, body planning, reproductive traits, and body regeneration. However, the mechanisms of maintenance of chloroplasts and photosynthesis in sea slugs are poorly understood. Here, we introduce this mysterious phenomenon, including recent research findings, and consider its feasibility for synthetic biology, e.g., construction of artificial photosynthetic animal cells.
Chromosomal information is important for taxonomic grouping and provides insight into the origin of and taxonomic relationships between taxa. Studies on the karyotype and chromosomal diversity of Taraxacum can lead to a better understanding of the taxonomy, phylogenetic taxonomic relationships, and diversities of the species in the genus. The present review focuses on the chromosomal divergences in the genus Taraxacum distributed in Japan from the viewpoint of plant cytotaxonomy.
Clerodendrum inerme is a traditionally used medicinal plant in tropical and subtropical regions of the world. The present study aimed to analyze the mitotic abnormality-inducing potentials of the leaf aqueous extract of C. inerme (LAECI) on Allium cepa root tip cells. The 48-h aged A. cepa roots were treated with LAECI (2, 4, and 8 mg mL−1) for 2 and 4 h and also allowed to recover up to 16 h and compared with the standard colchicine (0.4 mg mL−1) actions. The cytological study revealed that both the LAECI and colchicine treatments induced mitotic abnormalities like sticky and vagrant chromosomes, anaphase bridge, multipolar anaphase-telophase, etc. The present study indicates that the LAECI contains bioactive substances having colchicine-like mitotic abnormality-inducing effects on A. cepa root tip cells.
The Arabidopsis thaliana stomatal complex contains a pair of guard cells surrounded by subsidiary cells, which assist in turgor-driven stomatal movement and receive water and ions. This transport, driven by environmental signals, involves a translocation factor of the plasma membrane proton pump H+-ATPase AHA1, PATROL1. In this study, we investigated the responses of PATROL1 to salinity and hyperosmotic stresses. Specifically, we analyzed the effects of 125 mM NaCl or 231 mM mannitol on the cotyledon pavement cell cortexes in transgenic A. thaliana seedlings expressing green fluorescent protein (GFP)-tagged PATROL1. Cells treated with NaCl had few GFP-PATROL1-labeled dot-like structures but contained unusual labeled large bodies and rod-like structures. Cells treated with mannitol had similar large bodies, but not rods, indicating that the rod-like structures form specifically under salinity stress conditions. Dual observations of GFP-PATROL1 and red fluorescent protein (RFP)-tagged AHA1 in stress-treated cells revealed that the latter did not accumulate in the stress-induced GFP-PATROL1 structures, suggesting that the stress-induced GFP-PATROL1 structures are not involved in RFP-AHA1 localization. Additionally, the primary root growth of the patrol1 mutant was more sensitive to NaCl treatment than was that of wild type. Thus, PATROL1 appears to contribute to salinity stress tolerance, possibly by regulating membrane trafficking.
Ten germplasms of Crotalaria species viz. C. pallida, C. incana and C. juncea available in Bangladesh were investigated cytogenetically to find out the chromosomal variation. In C. pallida 2n=16 (Acc. No. 4803, 4805, and 4807) and 2n=18 (Acc. No. 4250 and 4806) chromosomes were observed. In contrast, C. incana was found to possess 2n=16 (Acc. No. 4801), 2n=17 (Acc. No. 4790 and 4804), and 2n=18 (Acc. No. 4809) chromosomes while 2n=16 was observed in C. juncea. Somatic chromosome number 2n=17 in Acc. No. 4790 and 4804 of C. incana might be originated either by intraspecific hybridization between 2n=18 and 2n=16 germplasm or by aneuploid origin that correlates with their phenotypic features like seedless pod formation. This information of these two germplasms can help to the further breeding program. The variation of chromosomal length in all germplasms was almost negligible. Metacentric chromosomes were found in most germplasms indicate their symmetric nature. In contrast, submetacentric chromosomes were observed in several germplasms of C. pallida and C. incana indicates a relatively asymmetric nature. Therefore, each germplasms of Crotalaria could be characterized authentically by cytogenetical analysis.
Begonia sect. Baryandra is distributed mainly in the Philippines with a few species in Borneo and New Guinea. Previous chromosome information of sect. Baryandra has restricted to ca. 16 species and their karyotypes have never been investigated. Here we report the cytological investigations of 26 species of sect. Baryandra, including five karyotype analyses that are the first report in sect. Baryandra, 24 species were reported cytologically for the first time, and two species were re-examined. Incorporating previous and present studies, chromosome numbers of 40 of the 78 species in sect. Baryandra are now available. Except for some intraspecific variant counts of 2n=26 and 44, and a tetraploid number of 2n=56, 39 species have the chromosome number of either 2n=28 or 30. The karyotypic formula of the three investigated species is uniform as 2n=28=10m+18sm(st), and two as 2n=30=8m+22sm(st). Based on molecular phylogenetic relationships, ancestral state reconstruction suggests that 2n=30 is the most likely ancestral chromosome number of sect. Baryandra, with 2n=28 a derived number. Based on our and previous studies, the chromosome evolution in Begonia sect. Baryandra is discussed.
Medicinally important five Phyllanthus species viz. P. acidus (L.) Skeels, P. emblica L. (small fruit form), P. emblica L. (large fruit form), P. niruri L., P. reticulatus Poir. and P. urinaria L. were cytogenetically studied through orcein-staining for authentic characterization. This genus showed variation in somatic chromosome numbers such as 2n=2x=26 (x=13) in P. acidus, P. niruri and P. reticulatus, 2n=6x=48 (x=8) in P. urinaria and 2n=10x=100 (x=10) in P. emblica (both small and large fruit forms), represented with multi-basic chromosome number. Formation of bivalents in addition to several multivalents at metaphase-I of P. emblica (both forms) indicated that this species has the possibility of being auto-allopolyploid or segmental-allopolyploid that are going through the process of diplodization.
Studying the genome evolution of Nicotiana has been hindered by the small chromosome and complex chromosomal number. Consequently, studying the chromosomal structure is a very important work in clarifying the genome evolution of genus Nicotiana. In the present study, the 18S and 5S rDNA sites of eight Nicotiana species were physically mapped by double-probe FISH. Results showed the following: 1) each species (including the S-genome and T-genome of N. tabacum) had one or two pairs of 5S rDNA sites and chromosome VIII of each species had one pair of 5S rDNA sites in the interstitial region of the long arm; 2) each species (including the S-genome and T-genome of N. tabacum) had one, two or three pairs of 18S rDNA sites; 3) the chromosomal distribution of 5S and 18S rDNA was same between N. setchellii, N. kawakamii and N. otophora, and between N. glutinosa and N. tomentosa; and the chromosomal distribution of 5S and 18S rDNA of N. sylvstris and N. tomentosiformis was same with the S-genome and T-genome of N. tabacum, respectively. Finally, the genome evolutions of the genus Nicotiana were inferred. The present results could provide obvious references for studies on the system and phylogenesis of genus Nicotiana and were of significance to genetic breeding and germplasm innovation for tobacco.
Pairing of homologous chromosomes (HCs) during meiosis is a vital process for the production of normal haploid gametes and fertile progeny. However, the pairing process, especially its initial steps, shows diversity among organisms and has not been fully understood. In order to expand our knowledge of plant meiosis, the behaviors of telomeres and 25S rRNA loci in Lamium amplexicaule (2n=18) were investigated using fluorescent in situ hybridization (FISH) experiments. Telomere signals were detected on small knot-like structures at the pachytene stage and on all nine bivalents at diakinesis. 25S rDNA signals were found on three bivalents, indicating that the L. amplexicaule genome has three 25S rRNA loci. During the prophase of meiosis I, 25S rDNA signals were observed approaching each other and frequently merging into a single cluster. Our results suggest that the clustering of 25S rRNA loci in L. amplexicaule could play a role in promoting homolog pairing at prophase I.
Alstonia venenata R. Br. (Family: Apocynaceae), a paleoendemic under ex situ conservation in north India has been cytologically investigated for chromosome counts. This study recorded chromosome count (n=11) for the species. The species existed at the diploid level. Most chromosomes were involved in the bivalent formation (67.65%) of the pollen mother cells (PMCs) observed at meiosis. However, two additional types (7ll+2IV and 9II+1IV) of chromosome association (multivalents) were observed in 32.35% of PMCs. The quadrivalents formed as a consequence of reciprocal translocations are either ring or chain type. Chiasma frequency is also studied. PMCs with more multivalents depicted relatively higher chiasma frequency than others. These chromosome associations resulted in high pollen sterility (80.33%). Scanning electron microscope (SEM) analysis has also been performed in pollen grains. Here in this paper, we are also presenting first time analysis of the meiotic course and occurrence of multivalents in an accession of the species. We also discuss the previous cytological studies done in the genus Alstonia. In spite of the occurrence of high pollen sterility, seed setting is normal which shows that the species has acclimatized to a greater extent in north India climatic conditions.
Induced polyploidy is well known to enhance the genetic architecture of plants that confers better survivorship to them in various agro-climatic conditions than their respective diploids. In this regard, the present study was aimed to obtain the autotetraploid of Commelina benghalensis through antimitotic agent colchicine in order to increase its commercial, ornamental, and medical value. For tetraploidy induction, ungerminated seeds and tips of cotyledon-stage seedlings of the plant were treated with various concentrations of colchicine (0.1, 0.15, 0.2, and 0.25%). Experiments carried out on ungerminated seeds were unsuccessful in generating stable polyploids as it causes the death of germinated seedlings at the very earliest stage. Conversely, applying aqueous colchicine solution constantly on tips of seedlings for 6–8 h per day for three consecutive days was found significant in producing stable tetraploids. Putative tetraploids were subjected to chromosomal, morphological, and palynological observations for their exact confirmation. Out of total 120 seedlings treated, six plants (5%) were found polyploid in C0 generation with the highest frequency (10%) observed in 0.2% colchicine. During meiosis, the PMCs of tetraploid plants exhibited 44 chromosomes in different associations like quadrivalent, trivalent, bivalent and univalent, while that of the control diploid plants showed regular 11 bivalents. Meiotic analysis showed a constant decrease of quadrivalent frequency and the increasing number of bivalents from C0 to C2 for better fertility. Furthermore, differences in vegetative and ornamental characteristics between diploid and polyploid plants were significant. The size of pollen grains, capsules, and seeds were significantly greater than those of diploid plants.
Karyotypes, C-banded heterochromatin, and silver-positive nucleolus organizer regions (Ag-NORs) of two anemonefish species, Amphiprion polymnus and Premnas biaculeatus, were studied and compared with those of previously reported species, A. clarkii, A. frenatus, and A. perideraion. The chromosome number was 2n=48 for all five species. The fundamental numbers (NF) in A. polymnus (NF=84) and P. biaculeatus (NF=90) were different from the three species (NF=86). Karyotypic differences among the species were found in the distribution of C-banded heterochromatin for large submetacentric chromosomes. Moreover, A. polymnus showed a peculiar C-banding pattern with telomeric C-bands distributed in all chromosomes. The Ag-NORs were commonly located in the terminal regions of the short arms of an acrocentric pair; however, the NOR-bearing chromosomes were different in size among the species. This study demonstrated that the karyotypes of A. polymnus and P. biaculeatus had different conditions from those of the three previously studied species and that the C-band patterns in large submetacentric chromosomes could be a potential reliable marker to distinguish the anemonefish.