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"Plant reproduction"
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The impact of heat stress in plant reproduction
The increment in global temperature reduces crop productivity, which in turn threatens food security. Currently, most of our food supply is produced by plants and the human population is estimated to reach 9 billion by 2050. Gaining insights into how plants navigate heat stress in their reproductive phase is essential for effectively overseeing the future of agricultural productivity. The reproductive success of numerous plant species can be jeopardized by just one exceptionally hot day. While the effects of heat stress on seedlings germination and root development have been extensively investigated, studies on reproduction are limited. The intricate processes of gamete development and fertilization unfold within a brief timeframe, largely concealed within the flower. Nonetheless, heat stress is known to have important effects on reproduction. Considering that heat stress typically affects both male and female reproductive structures concurrently, it remains crucial to identify cultivars with thermotolerance. In such cultivars, ovules and pollen can successfully undergo development despite the challenges posed by heat stress, enabling the completion of the fertilization process and resulting in a robust seed yield. Hereby, we review the current understanding of the molecular mechanisms underlying plant resistance to abiotic heat stress, focusing on the reproductive process in the model systems of Arabidopsis and Oryza sativa.
Journal Article
Revisiting the female germline cell development
The formation of the female germline is the fundamental process in most flowering plants’ sexual reproduction. In Arabidopsis , only one somatic cell obtains the female germline fate, and this process is regulated by different pathways. Megaspore mother cell (MMC) is the first female germline, and understanding MMC development is essential for comprehending the complex mechanisms of plant reproduction processes. Recently, more advanced technologies such as whole-mount single-molecule fluorescence in situ hybridization (smFISH), laser-assisted microdissection (LCM), chromatin immunoprecipitation/sequencing, and CRISPR gene editing have provided opportunities to reveal the mechanism of female germline development at different stages. Single-cell transcriptome/spatial transcriptomics analysis helps to investigate complex cellular systems at the single-cell level, reflecting the biological complexity of different cell types. In this review, we highlight recent progress that facilitates the development of the female germline to explore the roles of crucial gene regulatory networks, epigenetic pathways, cell-cycle regulators, and phytohormones in this process. This review discusses three key phases in female germline development and provides the possibility of distinct pathways restricting germline development in the future.
Journal Article
Landscape fragmentation and agricultural context impact pollination services to native annual plants in critically endangered Australian woodlands
Context
Agricultural intensification leads to habitat loss and fragmentation, disrupting plant-pollinator interactions directly and indirectly, through changes in landscape configuration and altered land-use practices. This has detrimental consequences for the persistence of plants, pollinators, and the ecosystem services they provide.
Objectives
We investigated the drivers by which landscape and agricultural context (what crops are being grown) impact pollination services and the reproductive success of native plant species in remnant vegetation within an agricultural mosaic landscape. Specifically, we evaluate the direct and indirect effects of landscape fragmentation (remnant size and edge effect) and the crop type adjacent to natural remnants on bee communities and native plants’ seed production.
Methods
We combined bee community surveys with field pollination experiments on four native annual plant species in core and edge remnants in the York gum-Jam woodlands of SW Western Australia, an endangered ecosystem. For each remnant, we recorded remnant size, adjacent crop type (canola or wheat), and local community predictors (floral abundance, canopy cover, and organic ground cover). We assessed how landscape and local community predictors influence bee communities and reproductive success in our focal plant species, to evaluate variation in pollination services across highly fragmented and isolated vegetation remnants.
Results
Bee abundance was higher in remnants adjacent to canola than wheat. Native bee abundance decreased, however, from the core to the edge of remnants adjacent to canola (but not wheat), suggesting a possible pollinator dilution effect next to flowering canola fields. Canola directly and indirectly increased seed production of the focal plant species, mediated by changes in bee abundance. Species-specific responses at the local scale resulted in higher pollen limitation in areas with abundant floral resources and low bee abundance.
Conclusions
Adjacent crop type, position within remnants, and remnant size are all associated with variation in bee abundances and plant reproduction. At local scales, variation in floral abundances relates to pollination services. Our findings indicate that adjacent crop type, combined with the abundance of bees (generalist insect pollinators) in remnant vegetation, impacts the reproductive success of native plants persisting in remnants of an endangered annual plant system within an intensively managed agricultural landscape.
Journal Article
Evolution and diversity of the angiosperm anther: trends in function and development
Key message
Anther development and dehiscence is considered from an evolutionary perspective to identify drivers for differentiation, functional conservation and to identify key questions for future male reproduction research.
Development of viable pollen and its timely release from the anther are essential for fertilisation of angiosperm flowers. The formation and subsequent dehiscence of the anther are under tight regulatory control, and these processes are remarkably conserved throughout the diverse families of the angiosperm clade. Anther development is a complex process, which requires timely formation and communication between the multiple somatic anther cell layers (the epidermis, endothecium, middle layer and tapetum) and the developing pollen. These layers go through regulated development and selective degeneration to facilitate the formation and ultimate release of the pollen grains. Insight into the evolution and divergence of anther development and dehiscence, especially between monocots and dicots, is driving greater understanding of the male reproductive process and increased, resilient crop yields. This review focuses on anther structure from an evolutionary perspective by highlighting their diversity across plant species. We summarise new findings that illustrate the complexities of anther development and evaluate how they challenge established models of anther form and function, and how they may help to deliver future sustainable crop yields.
Journal Article
Insights into the molecular evolution of fertilization mechanism in land plants
Key message
Comparative genetics and genomics among green plants, including algae, provide deep insights into the evolution of land plant sexual reproduction.
Land plants have evolved successive changes during their conquest of the land and innovations in sexual reproduction have played a major role in their terrestrialization. Recent years have seen many revealing dissections of the molecular mechanisms of sexual reproduction and much new genomics data from the land plant lineage, including early diverging land plants, as well as algae. This new knowledge is being integrated to further understand how sexual reproduction in land plants evolved, identifying highly conserved factors and pathways, but also molecular changes that underpinned the emergence of new modes of sexual reproduction. Here, we review recent advances in the knowledge of land plant sexual reproduction from an evolutionary perspective and also revisit the evolution of angiosperm double fertilization.
Journal Article
Flowering plant embryos: How did we end up here?
The seeds of flowering plants are sexually produced propagules that ensure dispersal and resilience of the next generation. Seeds harbor embryos, three dimensional structures that are often miniatures of the adult plant in terms of general structure and primordial organs. In addition, embryos contain the meristems that give rise to post-embryonically generated structures. However common, flowering plant embryos are an evolutionary derived state. Flowering plants are part of a much larger group of embryo-bearing plants, aptly termed Embryophyta. A key question is what evolutionary trajectory led to the emergence of flowering plant embryos. In this opinion, we deconstruct the flowering plant embryo and describe the current state of knowledge of embryos in other plant lineages. While we are far yet from understanding the ancestral state of plant embryogenesis, we argue what current knowledge may suggest and how the knowledge gaps may be closed.
Journal Article
The evolution of imprinting in plants: beyond the seed
Genomic imprinting results in the biased expression of alleles depending on if the allele was inherited from the mother or the father. Despite the prevalence of sexual reproduction across eukaryotes, imprinting is only found in placental mammals, flowering plants, and some insects, suggesting independent evolutionary origins. Numerous hypotheses have been proposed to explain the selective pressures that favour the innovation of imprinted gene expression and each differs in their experimental support and predictions. Due to the lack of investigation of imprinting in land plants, other than angiosperms with triploid endosperm, we do not know whether imprinting occurs in species lacking endosperm and with embryos developing on maternal plants. Here, we discuss the potential for uncovering additional examples of imprinting in land plants and how these observations may provide additional support for one or more existing imprinting hypotheses.
Journal Article
Boosting autophagy in sexual reproduction
The key process of sexual reproduction is the successful fusion of the sperm and egg cell. Distinct from dynamic and flagellated animal sperm cells, higher flowering plant sperm cells are immotile. Therefore, plants have evolved a novel reproductive system to achieve fertilization and generate progenies. Plant sexual reproduction consists of multiple steps, mainly including gametophyte development, pollen–pistil recognition, pollen germination, double fertilization and postfertilization. During reproduction, active production, consumption and recycling of cellular components and energy are critically required to achieve fertilization. However, the underlying machinery of cellular degradation and turnover remains largely unexplored. Autophagy, the major catabolic pathway in eukaryotic cells, participates in regulating multiple aspects of plant activities, including abiotic and biotic stress resistance, pathogen response, senescence, nutrient remobilization and plant development. Nevertheless, a key unanswered question is how autophagy regulates plant fertilization and reproduction. Here, we focus on comparing and contrasting autophagy in several key reproductive processes of plant and animal systems to feature important distinctions and highlight future research directions of autophagy in angiosperm reproduction. We further discuss the potential crosstalk between autophagy and programmed cell death, which are often considered as two disconnected events in plant sexual reproduction.
Journal Article
The epigenetic origin of life history transitions in plants and algae
Plants and algae have a complex life history that transitions between distinct life forms called the sporophyte and the gametophyte. This phenomenon—called the alternation of generations—has fascinated botanists and phycologists for over 170 years. Despite the mesmerizing array of life histories described in plants and algae, we are only now beginning to learn about the molecular mechanisms controlling them and how they evolved. Epigenetic silencing plays an essential role in regulating gene expression during multicellular development in eukaryotes, raising questions about its impact on the life history strategy of plants and algae. Here, we trace the origin and function of epigenetic mechanisms across the plant kingdom, from unicellular green algae through to angiosperms, and attempt to reconstruct the evolutionary steps that influenced life history transitions during plant evolution. Central to this evolutionary scenario is the adaption of epigenetic silencing from a mechanism of genome defense to the repression and control of alternating generations. We extend our discussion beyond the green lineage and highlight the peculiar case of the brown algae. Unlike their unicellular diatom relatives, brown algae lack epigenetic silencing pathways common to animals and plants yet display complex life histories, hinting at the emergence of novel life history controls during stramenopile evolution.
Journal Article