The molecular pathways that trigger the initiation of embryogenesis after fertilization in flowering plants, and prevent its occurrence without fertilization, are not well understood
. Here we show ...in rice (Oryza sativa) that BABY BOOM1 (BBM1), a member of the AP2 family
of transcription factors that is expressed in sperm cells, has a key role in this process. Ectopic expression of BBM1 in the egg cell is sufficient for parthenogenesis, which indicates that a single wild-type gene can bypass the fertilization checkpoint in the female gamete. Zygotic expression of BBM1 is initially specific to the male allele but is subsequently biparental, and this is consistent with its observed auto-activation. Triple knockout of the genes BBM1, BBM2 and BBM3 causes embryo arrest and abortion, which are fully rescued by male-transmitted BBM1. These findings suggest that the requirement for fertilization in embryogenesis is mediated by male-genome transmission of pluripotency factors. When genome editing to substitute mitosis for meiosis (MiMe)
is combined with the expression of BBM1 in the egg cell, clonal progeny can be obtained that retain genome-wide parental heterozygosity. The synthetic asexual-propagation trait is heritable through multiple generations of clones. Hybrid crops provide increased yields that cannot be maintained by their progeny owing to genetic segregation. This work establishes the feasibility of asexual reproduction in crops, and could enable the maintenance of hybrids clonally through seed propagation
.
SUMMARY
Natural plants must actively allocate their limited resources for survival and reproduction. Although vegetative growth, sexual reproduction, asexual reproduction and defense are all basic ...processes in the life cycle of plants, the strategies used to allocate resources between these processes are poorly understood. These processes are conspicuous in naturally grown Aconitum kusnezoffii Reichb., which makes it a suitable study subject. Here, the morphology, dry matter, total organic carbon, total nitrogen and aconitum alkaloid levels of shoot, principal root (PR) and lateral roots were measured throughout the growing season. Then, transcriptome and metabolite content analyses were performed. We found that vegetative growth began first. After vegetative growth ceased, sexual development began. Flower organ development was accompanied by increased photosynthesis and the PR consumed temporarily stored resources after flower formation. Asexual propagule development initiated earlier than sexual reproduction and kept accumulating resources after that. Development was slow before flower formation, mainly manifesting as increasing length; then, after flower formation it accelerated via enhanced material transport and accumulation. Defense compounds were maintained at low levels before flowering. In particular, the turnover of defense compounds was enhanced before and after flower bud emergence, providing resources for other processes. After flower formation, defense compounds were accumulated. The pattern found herein provides a vivid example for further studies on resource allocation strategies. The exciting finding that the PR, as a more direct storage site for photosynthate, is a buffer unit for resources, and that defense compounds can be reused for other processes, suggests a need to explore potential mechanisms.
Significance Statement
The pattern found herein provides a vivid example for further studies on resource allocation strategies among vegetative growth, sexual reproduction, asexual reproduction and defense. The exciting finding that the principal root, as a more direct storage site for photosynthate, is a buffer unit for resources, and that defense compounds can be reused for other processes (i.e., growth and reproduction) suggests a need to explore potential mechanisms.
Aspergillus niger reproduces asexually by forming conidia. Here, the minimal nutrient requirements were studied that activate germination of A. niger conidia. To this end, germination was monitored ...in time using an oCelloScope imager. Data was used as input in an asymmetric model to describe the process of swelling and germ tube formation. The maximum number of spores (Pmax) that were activated to swell and to form germ tubes was 32.54% and 20.51%, respectively, in minimal medium with 50 mM glucose. In contrast, Pmax of swelling and germ tube formation was <1% in water or 50 mM glucose. Combining 50 mM glucose with either NaNO3, KH2PO4, or MgSO4 increased Pmax of swelling and germination up to 15.25% and 5.4%, respectively, while combining glucose with two of these inorganic components further increased these Pmax values up to 25.85% and 10.99%. Next, 10 mM amino acid was combined with a phosphate buffer and MgSO4. High (e.g. proline), intermediate and low (e.g. cysteine) inducing amino acids were distinguished. Together, a combination of an inducing carbon source with either inorganic phosphate, inorganic nitrogen or magnesium sulphate is the minimum requirement for A. niger conidia to germinate.
•Germination of Aspergillus niger conidia in an inducing medium is heterogeneous.•An inducing C-source and either PO43−, NO3-, or MgSO4 activate germination of >5% of the conidia.•Of the proteinogenic amino acids, proline and alanine most strongly induce germination.•Cysteine is a lowly inducing or even a non-inducing amino acid for germination.
Cultivated potatoes (Solanum tuberosum L.), domesticated from wild Solanum species native to the Andes of southern Peru, possess a diverse gene pool representing more than 100 tuber-bearing relatives ...(Solanum section Petota). A diversity panel of wild species, landraces, and cultivars was sequenced to assess genetic variation within tuber-bearing Solanum and the impact of domestication on genome diversity and identify key loci selected for cultivation in North and South America. Sequence diversity of diploid and tetraploid S. tuberosum exceeded any crop resequencing study to date, in part due to expanded wild introgressions following polyploidy that captured alleles outside of their geographic origin. We identified 2,622 genes as under selection, with only 14–16% shared by North American and Andean cultivars, showing that a limited gene set drove early improvement of cultivated potato, while adaptation of upland (S. tuberosum group Andigena) and lowland (S. tuberosum groups Chilotanum and Tuberosum) populations targeted distinct loci. Signatures of selection were uncovered in genes controlling carbohydrate metabolism, glycoalkaloid biosynthesis, the shikimate pathway, the cell cycle, and circadian rhythm. Reduced sexual fertility that accompanied the shift to asexual reproduction in cultivars was reflected by signatures of selection in genes regulating pollen development/gametogenesis. Exploration of haplotype diversity at potato’s maturity locus (StCDF1) revealed introgression of truncated alleles from wild species, particularly S. microdontum in long-day–adapted cultivars. This study uncovers a historic role of wild Solanum species in the diversification of long-day–adapted tetraploid potatoes, showing that extant natural populations represent an essential source of untapped adaptive potential.
The Guadalupe cypress (Cupressus guadalupensis S. Watson) is an endangered species included in the list of the NOM-059-SEMARNAT-2010. The presence of wild goats in the habitat has been the greatest ...threat to the propagation and survival of this species. Therefore, there is a need to generate propagation protocols that facilitate the regeneration of the species. Plant tissue culture offers various possibilities that can facilitate the regeneration of species under some risk. Temporary immersion systems have proven to be an option with various advantages in plant tissue culture, such as increasing the number of seedlings generated and reducing production times, compared to semisolid media. The objective of this chapter is to describe a protocol to propagate Guadalupe cypress tissues in a RITA
temporary immersion system.
The fixed life pattern of plants is the most threatening factor that hinders the survival and reproduction rate of plants. Maximization of reproduction is determined by the survival rate of the ...organism. If part of a shoot apical meristem or root apical meristem is cut and planted in soil with appropriate nutrients and survival conditions, a cloned plant known as an ramet, may be developed. Therefore, the ability of plants to constantly produce meristems is essential for survival. In addition, meristem stem cells have enabled plants to evolve a wide variety of asexual reproductive systems. When a tree is pruned, at least one or more new meristems are formed in the surrounding area, and those meristems develop into new branches. In other cases, stem cells normally derived from meristems alone exhibit the potential for asexual reproduction through their seed-like roles. Alternatively, some plants can form somatic cells, which are important in various types of asexual reproduction. There are 125 species of plants in the genus of Kalanchoe, which are succulent plants, and most of these species are well known to reproduce asexually through somatic cells. When we cut the stem of a plant, a callus is formed at the end of the cut side. Plant callus is mainly used to develop new plant varieties in tissue culture research. Alternatively, the plant callus is also used as a material for asexual reproduction. Callus can also form if the plant is infected with bacteria such as Agrobacterium tumefaciens. Differentiated cells of a plant can reproduce asexually by acquiring the ability to function as stems through transdifferentiation. These characteristics play important roles in adapting to environmental changes and extending the lifespan of woody plants.
Heterosis, or hybrid vigor, is exploited by breeders to produce elite high-yielding crop lines, but beneficial phenotypes are lost in subsequent generations owing to genetic segregation. Clonal ...propagation through seeds would enable self-propagation of F
hybrids. Here we report a strategy to enable clonal reproduction of F
rice hybrids through seeds. We fixed the heterozygosity of F
hybrid rice by multiplex CRISPR-Cas9 genome editing of the REC8, PAIR1 and OSD1 meiotic genes to produce clonal diploid gametes and tetraploid seeds. Next, we demonstrated that editing the MATRILINEAL (MTL) gene (involved in fertilization) could induce formation of haploid seeds in hybrid rice. Finally, we combined fixation of heterozygosity and haploid induction by simultaneous editing of all four genes (REC8, PAIR1, OSD1 and MTL) in hybrid rice and obtained plants that could propagate clonally through seeds. Application of our method may enable self-propagation of a broad range of elite F
hybrid crops.
Development in Aspergillus Krijgsheld, P.; Bleichrodt, R.; van Veluw, G.J. ...
Studies in mycology,
03/2013, Volume:
74, Issue:
1
Journal Article
Peer reviewed
Open access
The genus Aspergillus represents a diverse group of fungi that are among the most abundant fungi in the world. Germination of a spore can lead to a vegetative mycelium that colonizes a substrate. The ...hyphae within the mycelium are highly heterogeneous with respect to gene expression, growth, and secretion. Aspergilli can reproduce both asexually and sexually. To this end, conidiophores and ascocarps are produced that form conidia and ascospores, respectively. This review describes the molecular mechanisms underlying growth and development of Aspergillus.
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