Morphological characterization and genetic analysis of tri-pistil trait, a precisely regulated pistil number mutation in bread wheat

Bread wheat (Triticum aestivum L.) is an important source of nutrients for humans. Therefore, improvement of its yields is essential to feed the increasing world population. The tri-pistil (TRP) trait in wheat has a high potential for increasing yields. We obtained a pure tri-pistil wheat line, 4045, and evaluated its morphological properties. The 4045 wheat line stably produced three independently inherited pistils, which led to 1-3 grains in each floret. Among the three pistils, two lately emerged pistils initiated at late anther primordia stage to early tetrads stage. Genetic analysis revealed that there were TRP penetrance variations among the 11 F1 populations of 4045. Fine mapping narrowed the single dominant TRP locus to a 97.3 kb region, containing two candidate genes, on the 2DL chromosome. However, further gene sequence, functional as well as comparative genomic analyses ruled out the only two candidate genes. Therefore, TRP is high-likely a unique gain-of-function mutation that does not exist in normal wheat genome. Transcriptome analysis of floral homeotic genes revealed that expressions of the C-class TaAG-2s, which are essential for carpel specification, significantly increased in 4045, implying that TaAG-2s have played important roles in TRP-regulated tri-pistil formation. This study highlights that TRP leads to a precisely regulated pistil number increase (PRPNI) mutations and proposed a regulatory model of PRPNI pistil architecture. PRPNI offers a novel abnormal pistil development resource for research of floral architectures and potential on crop yield improvement.

A Novel Embryo Phenotype Associated With Interspecific Hybrid Weakness in Rice Is Controlled by the MADS-Domain Transcription Factor OsMADS8

A novel hybrid weakness gene, DTE9, associated with a dark tip embryo (DTE) trait, was observed in CR6078, an introgression line derived from a cross between the Oryza sativa spp. japonica “Hwayeong” (HY) and the wild relative Oryza rufipogon. CR6078 seeds exhibit protruding embryos and flowers have altered inner floral organs. DTE9 was also associated with several hybrid weakness symptoms including decreased grain weight. Map-based cloning and transgenic approaches revealed that DTE9 is an allele of OsMADS8, a MADS-domain transcription factor. Genetic analysis indicated that two recessive complementary genes were responsible for the expression of the DTE trait. No sequence differences were observed between the two parental lines in the OsMADS8 coding region; however, numerous single nucleotide polymorphisms were detected in the promoter and intronic regions. We generated overexpression (OX) and RNA interference (RNAi) transgenic lines of OsMADS8 in HY and CR6078, respectively. The OsMADS8-OX lines showed the dark tip embryo phenotype, whereas OsMADS8-RNAi recovered the normal embryo phenotype. Changes in gene expression, including of ABCDE floral homeotic genes, were observed in the OsMADS8-OX and OsMADS8-RNAi lines. Overexpression of OsMADS8 led to decreased expression of OsEMF2b and ABA signaling-related genes including OsVP1/ABI3. HY seeds showed higher ABA content than CR6078 seeds, consistent with OsMADS8/DTE9 regulating the expression of genes related ABA catabolism in CR6078. Our results suggest that OsMADS8 is critical for floral organ determination and seed germination and that these effects are the result of regulation of the expression of OsEMF2b and its role in ABA signaling and catabolism.

Genetic insights into the regulatory pathways for continuous flowering in a unique orchid Arundina graminifolia

Background Manipulation of flowering time and frequency of blooming is key to enhancing the ornamental value of orchids. Arundina graminifolia is a unique orchid that flowers year round, although the molecular basis of this flowering pattern remains poorly understood. Results We compared the A. graminifolia transcriptome across tissue types and floral developmental stages to elucidate important genetic regulators of flowering and hormones. Clustering analyses identified modules specific to floral transition and floral morphogenesis, providing a set of candidate regulators for the floral initiation and timing. Among candidate floral homeotic genes, the expression of two FT genes was positively correlated with flower development. Assessment of the endogenous hormone levels and qRT-PCR analysis of 32 pathway-responsive genes supported a role for the regulatory networks in floral bud control in A. graminifolia. Moreover, WGCNA showed that flowering control can be delineated by modules of coexpressed genes; especially, MEgreen presented group of genes specific to flowering. Conclusions Candidate gene selection coupled with hormonal regulators brings a robust source to understand the intricate molecular regulation of flowering in precious orchids.

Study of Cananga odorata (Lam.) Hook. f. & Thoms. Flower Development: Morphological Variations in an Urban Environment

Cananga odorata is a native plant in the Indonesian archipelago. The flowers are often used to produce essential oils with many uses and a distinct fragrance. This study aims to observe each stage of the Cananga odorata flower development. The flowers were obtained from a home garden in Pasar Minggu, South Jakarta, from November 2020 until January 2021. Further observations of the stamen and pistil developments were conducted using Dino-Lite Edge Digital Microscope AM4115 Series. The results show that Cananga odorata flower development can be categorized into bud, display-petal, initial-flowering, full-flowering, end-flowering, and senescence stages. The flowers require 35 days to develop from bud stage to flower senescence. Stamens and pistils also develop primarily during the bud stages and mature after flower anthesis. Flower mutants were also found and may be caused by a mutation in the flower’s homeotic genes. Each different stages of flower development show a different morphological change in the flower perianth and reproductive organs. A discrepancy of flower morphology within each stage, especially those seen during the anthesis stages, might imply a variation in the flower’s internal factors.

Homeotic Genes: Clustering, Modularity, and Diversity

Hox genes code for transcription factors and are evolutionarily conserved. They regulate a plethora of downstream targets to define the anterior-posterior (AP) body axis of a developing bilaterian embryo. Early work suggested a possible role of clustering and ordering of Hox to regulate their expression in a spatially restricted manner along the AP axis. However, the recent availability of many genome assemblies for different organisms uncovered several examples that defy this constraint. With recent advancements in genomics, the current review discusses the arrangement of Hox in various organisms. Further, we revisit their discovery and regulation in Drosophila melanogaster. We also review their regulation in different arthropods and vertebrates, with a significant focus on Hox expression in the crustacean Parahyale hawaiensis. It is noteworthy that subtle changes in the levels of Hox gene expression can contribute to the development of novel features in an organism. We, therefore, delve into the distinct regulation of these genes during primary axis formation, segment identity, and extra-embryonic roles such as in the formation of hair follicles or misregulation leading to cancer. Toward the end of each section, we emphasize the possibilities of several experiments involving various organisms, owing to the advancements in the field of genomics and CRISPR-based genome engineering. Overall, we present a holistic view of the functioning of Hox in the animal world.

Selective Requirement for Polycomb Repressor Complex 2 in the Generation of Specific Hypothalamic Neuronal Sub-types

The hypothalamus displays staggering cellular diversity, chiefly established during embryogenesis by the interplay of several signalling pathways and a battery of transcription factors. However, the contribution of epigenetic cues to hypothalamus development remains unclear. We mutated the Polycomb Repressor Complex 2 gene Eed in the developing mouse hypothalamus, which resulted in the loss of H3K27me3; a fundamental epigenetic repressor mark. This triggered ectopic expression of posteriorly expressed regulators (e.g., Hox homeotic genes), upregulation of cell cycle inhibitors and reduced proliferation. Surprisingly, despite these effects, single cell transcriptomic analysis revealed that the majority of neuronal subtypes were still generated in Eed mutants. However, we observed an increase in Glutamatergic/GABAergic double-positive cells, as well as loss/reduction of dopamine, Hypocretin/Orexin and Tac2 neurons. These findings indicate that many aspects of the hypothalamic gene regulatory flow can proceed without the key H3K27me3 epigenetic repressor mark, and points to a unique sensitivity of particular neuronal sub-types to a disrupted epigenomic landscape.

Drosophila architectural protein CTCF is not essential for fly survival and is able to function independently of CP190

CTCF is the most likely ancestor of proteins that contain large clusters of C2H2 zinc finger domains (C2H2) and is conserved among most bilateral organisms. In mammals, CTCF functions as the main architectural protein involved in the organization of topology-associated domains (TADs). In vertebrates and Drosophila, CTCF is involved in the regulation of homeotic genes. Previously, null mutations in the dCTCF gene were found to result in death during the stage of pharate adults, which failed to eclose from their pupal case. Here, we obtained several new null dCTCF mutations and found that the complete inactivation of dCTCF appears to be limited to phenotypic manifestations of the Abd-B gene and fertility of adult flies. Many modifiers that are not associated with an independent phenotypic manifestation can significantly enhance the expressivity of the null dCTCF mutations, indicating that other architectural proteins are able to functionally compensate for dCTCF inactivation in Drosophila. We also mapped the 715-735 aa region of dCTCF as being essential for the interaction with the BTB (Broad-Complex, Tramtrack, and Bric a brac) and microtubule-targeting (M) domains of the CP190 protein, which binds to many architectural proteins. However, the mutational analysis showed that the interaction with CP190 was not essential for the functional activity of dCTCF in vivo.

Overexpression of SlMBP22 in Tomato Affects Flower Morphology, Fruit Set and Development

MADS-domain transcription factors have been clarified as key regulators involved in proper flower and fruit development in angiosperms. Bs genes, as members of the MADS-box subfamily, have been suggested to play an important role during the evolution of the reproductive organs in seed plants. Our knowledge about their effects on reproductive development in fruit crops like tomato (Solanum lycopersicum), however, is still unclear. Here, we found that the overexpression of SlMBP22 (SlMBP22-OE) resulted in considerable alterations regarding floral morphology, and affected the expression levels of several floral homeotic genes. Further analysis by yeast-two-hybrid assays demonstrated that SlMBP22 could form dimers with class A protein MACROCALYX (MC) and with SEPALLATA (SEP) floral homeotic proteins TM5 and TM29, respectively. In addition, pollen viability and cross-fertilization assays suggested that the defect in female reproductive development was responsible for infertility phenotype observed in the strong overexpression transgenic plants. The mild overexpression transgenic fruits were reduced in size, as a result of reduced cell expansion, rather than impaired cell division. Additionally, overexpression of SlMBP22 in tomato not only affected proanthocyanidin (PA) accumulation but also altered seed dormancy. Taken together, these findings may provide new insights into the knowledge of Bs MADS-box genes in flower and fruit development in tomato.

Ewolucja. Twórcza moc selekcji

An instructive introduction to the theory of evolution and its applications in biology, physics, chemistry, geology and humanities. The author shows that evolution is a physical process, occurring in geological time dimension, describes how the Darwin’s theory of natural selection works in immunology, neurobiology, sociology as well as in certain aspects of culture and political institutions. He also shows the effects achieved through the action of selection in different areas of biological and social life. He discusses such problems as: the ambiguity of the term “theory of evolution”, the falsifiability of evolutionary hypotheses, connection between evolution and thermodynamics, the concept of reductionism, methodological background of phylogenetics, cladistics, evolutionary developmental biology and homeotic genes, as well as the cumulative nature of social and cultural evolution.