Plants (algae and land plants) can trace their origins to symbiotic relationships between cyanobacteria-like photosynthetic bacteria and host cells. This process known as primary endosymbiosis gave rise to red algae, green plants, and glaucophyte algae. A number of hypotheses have been put forth to explain how the primary endosymbiosis was established and how the endosymbiont DNA was transferred horizontally into the host genome. This review focuses on these hypotheses concerning primary endosymbiosis and introduces the characteristics and rationale of each hypothesis. Recent advances in molecular biology and genome technology for a more sophisticated understanding of the mechanisms of primary endosymbiosis will also be discussed.

Plant development depends on the activity of meristems, such as the shoot apical meristem and flower meristem. These meristems contain pluripotent stem cells that proliferate for self-renewal or for cell supply for the differentiation of lateral organs including leaves and floral organs. The regulation of the balance between self-renewal and the supply of cells for differentiation is referred to as stem cell homeostasis, which is essential for sustainable plant development. Extensive studies in the model eudicot Arabidopsis (Arabidopsis thaliana) have demonstrated that WUSCHEL (WUS), a gene encoding a WOX transcription factor, plays a central role in maintaining stem cell homeostasis. Several studies in the model monocot rice (Oryza sativa) over the past decade have revealed the function of the WUS ortholog, TILLERS ABSENT1 (TAB1), whose developmental role is somewhat different from that of WUS. This review describes the roles of WUS/TAB1 in stem cell maintenance, highlighting both conserved and species-specific functions, as well as their additional roles in reproductive organogenesis.

In this study, three tandem repeats were identified from the genome of the Capsicum annuum L. C26 and C37 were satellite repeats, and C28 was a minisatellite repeat. Monomers of C26, C37, and C28 were 152 bp, 37 bp, and 180 bp respectively. Fluorescence in situ hybridization (FISH) results revealed that signals of C26 were located at the centromeric region of a pair of chromosomes and the subtelomeric region of a pair of chromosomes; signals of C28 were located on eight pairs of chromosomes; signals of C37 were mainly located at the subterminal region of all chromosomes, but some signals at one end of the chromosome and some at both ends of the chromosome. Furthermore, double-color FISH results showed that seven pairs of chromosomes could be reliably distinguished by specific FISH signals of C28+C37. It will help to construct molecular karyotypes, reveal new chromosome rearrangements, and improve chromosome engineering breeding of the Capsicum genus.

Cultivated alfalfa (Medicago sativa L.) is one of the most important forage crops grown all over the world. The karyotype of cultivated alfalfa based on fluorescence in situ hybridization (FISH) pattern is rarely reported. In this study, the oligonucleotide FISH (Oligo-FISH) karyotype pattern of alfalfa was obtained using probes Oligo-MsTR1, Oligo-MsCR3, Oligo-E180, 5S rDNA and 18S–26S rDNA. The results showed that 5S rDNA and 18S–26S rDNA signal distributions were conserved. Moreover, the signal patterns of the probes Oligo-E180, Oligo-MsTR1, and Oligo-MsCR3 displayed polymorphism on part of the alfalfa chromosomes. Chromosome 11 exhibits 6 variants, showing the highest polymorphism, and chromosomes 1 and 12 display 5 polymorphisms, indicating higher genetic diversity between these chromosomes. Chromosomes 3, 4, and 16 are conserved and show monomorphic, illustrating the lower genetic diversity among these three chromosomes. The level of genetic diversity can provide a theoretical basis for alfalfa hybrid breeding. In addition, the FISH karyotype of cultivated alfalfa chromosomes constructed in this study provides a reference for future analysis of alfalfa genetic stocks.

The Alpinia species (A. intermedia, A. zerumbet, A. formosana, A. uraiensis, and unidentified strains native to the Daito Islands), which are native to the Nansei Islands, Japan are ornamental plants that can be used as resources to produce seasonings and antibacterial and antiviral substances. Despite the usefulness of these plants, little scientific research has been conducted on their phylogenetic relationships. In this study, their phylogenetic relationships were examined based on genomic and chloroplast DNA polymorphisms, repetitive sequence abundance, and cytogenetic perspectives. The results indicated that A. formosana is most likely the outcome of a hybrid of A. zerumbet and A. intermedia, and the unidentified strains native to the Daito Islands are the outcomes of a hybrid of A. zerumbet and A. uraiensis. Immunostaining with a newly produced anti-centromere-specific histone H3 (CENH3) antibody revealed that the number of chromosomes in these species was 2n=48.

To infer the cytological evolutionary mechanism of the genus Hosta, we analyzed chromosome numbers and karyotypes obtained via Feulgen staining, and measured genome size by flow cytometry. While the chromosome number of all the studied plants was consistently 2n=60, the total haploid chromosome length varied from 55.37 µm in H. jonesii to 76.22 µm in H. yingeri. Bimodal karyotypes in chromosome size variation were observed in all Hosta taxa studied. The C-value was relatively high in all studied taxa, ranging from 7.94 pg C⁻¹ in H. minor to 10.92 pg C⁻¹ in H. kikutii var. polyneuron, further supporting the evolution of variable genome sizes in Hosta. The comprehensive cytological results provide a framework for detailed molecular cytogenetic and phylogenomic analyses, thereby enhancing our understanding of diversification in Hosta, independent of stable chromosome numbers.

The subject of research was a molecular cytogenetic investigation of the Hemidactylus frenatus or spiny-tailed house gecko. Ag-nucleolar organizer region (NOR) banding, fluorescence in situ hybridization (FISH), and conventional staining were used to mitotic chromosomes prepared directly from bone marrow. According to the findings, there were 40 diploid chromosomes (2n). For both sexes, the fundamental number was 74. The karyotype formula, consisting of metacentric, submetacentric, acrocentric, and telocentric chromosomes, is as follows: 2n(40)=10m+4sm+20a+6t or L₂^m+L₄^sm+L₈^a+M₆^a+S₈^m+S₆^a+S₆^t. The NORs appeared at the telomere of the long arm of chromosome pair 16. Using six probes, (A)₃₀, (CA)₁₅, (GC)₁₅, (CAC)₁₀, (GAA)₁₀, and (GAG)₁₀, FISH mapping of microsatellite repeat modes was conducted. The results showed specific signals of (CA)₁₅, (GC)₁₅, (CAC)₁₀, (GAA)₁₀, and (GAG)₁₀ on chromosome pairs, whereas the (A)₃₀ probe spread onto metaphase. H. frenatus chromosomes are primarily acrocentric, and all of their chromosomes have distinct patterns in their short and long arms. This characteristic is maintained by the main evolutionary line of the gecko group, including its early predecessors. The evolution of the karyotype in the genus Hemidactylus involved the breaking off of chromosomal fragments and the rearrangement of centromeres, resulting in different numbers and shapes of chromosomes within the genus.

In this study, specimens of Iris pseudopumila and I. bicapitata from various habitats on the Gargano Peninsula (Puglia region, Italy) were karyologically analyzed. The chromosome numbers and karyotype features of the two species were investigated by Feulgen staining. I. pseudopumila exhibited a chromosome number of 2n=16, while I. bicapitata had 2n=40. Significant differences in karyotypic indices were observed among the populations of I. pseudopumila. In purple-flowered specimens, the number of subtelocentric and telocentric chromosomes differed from that of the yellow-flowered specimens. Notably, cases of heteromorphy were observed in some chromosome pairs. These findings reveal structural changes in the chromosomes of the studied I. pseudopumila populations, reflecting an ongoing evolutionary process within this species. The variation in the karyotype formula seen in I. pseudopumila suggests karyotype instability, with ongoing genomic changes and chromosomal rearrangements. In contrast, I. bicapitata showed little karyotype variation between the short- and long-stem specimens. The data obtained for these two species can enhance insights into the mechanisms of species evolution within the genus Iris.

Solanum melongena is one of the tremendously valuable vegetable crops in India, co-existing with its closest wild relative, S. insanum. Given the very few reports on chromosome analysis, the necessity of detailed karyotype investigation in wild and cultivated eggplants was felt. The present work addresses the adoption of an advanced chromosome preparation method for the analysis of ‘small-sized chromosomes’ of eggplants. The employment of enzymatic maceration and air drying (EMA) method enabled comparative analysis of karyotype features of the two allied species based on Giemsa-DAPI (4′-6-diamidino-2-phenylindole) staining. The study offers a reproducible yet simple technique of eggplant chromosome preparation for the first time in Indian populations, opening the scope for chromosome banding or in situ hybridization.

Chromosome numbers of seven taxa of Cyperus L. (Cyperaceae) collected from Japan are presented. Our findings differ from previous reports and are as follows: 2n=58 for C. brevifolius (Rottb.) Hassk. var. leiolepis (Franch. & Sav.) T.Koyama, 2n=50 for C. distans L.f., 2n=44 for C. eragrostis Lam., 2n=30 for C. flaccidus R.Br., 2n=64 for C. flavidus Retz., 2n=28 for C. haspan L., and 2n=64 for C. tenuispica Steud.

Begonia cucullata (Begoniaceae) is an ornamental plant used in gardening and landscaping that is capable of flowering in four seasons and possesses strong resistance to abiotic stresses, giving it considerable commercial value. Research on B. cucullata currently focuses mainly on cultivation-related physiology, while less attention is paid to ploidy and karyotype identification. In this study, one important wild Begonia species, and five horticultural varieties of B. cucullata were used as experimental materials for karyotype analysis. The results indicate that the ploidy of wild species is 2n=34, while the variety ‘Big Series’ is a tetraploid (2n=68). These findings are of considerable importance for breeding varieties of Begonia with excellent horticultural traits.

Male meiotic studies were carried out in 13 accessions of species belonging to the genus Mammillaria. Accessions of Mammilaria beneckei Ehrenb. and M. petterssonii Hildm. were observed to bear the gametophytic chromosome number of n=11. This is the first report on the chromosome number of these species. Gametophytic chromosome number of n=11 was observed in accessions of M. carnea Zucc. ex Pfeiff, M. compressa DC., M. elongata subsp. echinaria (DC.) D. R. Hunt, and M. magnimamma Haw. These taxa have been cytologically worked out for the first time in India. Chromosome numbers for four taxa, M. carmenae Castañeda (n=11), M. plumosa F.A.C. Weber (n=11), M. prolifera (Mill.) Haw. (n=22), and M. prolifera subsp. texana (Engelm.) D.R. Hunt (n=22) were validated with previous reports.