HEARTBREAK Controls Post-translational Modification of INDEHISCENT to Regulate Fruit Morphology in Capsella

Evolution of a SHOOTMERISTEMLESS transcription factor binding site promotes fruit shape determination

In animals and plants, organ shape is primarily determined during primordium development by carefully coordinated growth and cell division1-3. Rare examples of post-primordial change in morphology (reshaping) exist that offer tractable systems for the study of mechanisms required for organ shape determination and diversification. One such example is morphogenesis in Capsella fruits whose heart-shaped appearance emerges by reshaping of the ovate spheroid gynoecium upon fertilization4. Here we use whole-organ live-cell imaging and single-cell RNA sequencing (scRNA-seq) analysis to show that Capsella fruit shape determination is based on dynamic changes in cell growth and cell division coupled with local maintenance of meristematic identity. At the molecular level, we reveal an auxin-induced mechanism that is required for morphological alteration and ultimately determined by a single cis-regulatory element. This element resides in the promoter of the Capsella rubella SHOOTMERISTEMLESS5 (CrSTM) gene. The CrSTM meristem identity factor positively regulates its own expression through binding to this element, thereby providing a feed-forward loop at the position and time of protrusion emergence to form the heart. Independent evolution of the STM-binding element in STM promoters across Brassicaceae species correlates with those undergoing a gynoecium-to-fruit shape change. Accordingly, genetic and phenotypic studies show that the STM-binding element is required to facilitate the shape transition and suggest a conserved molecular mechanism for organ morphogenesis.

Cellular mechanism of polarized auxin transport on fruit shape determination revealed by time-lapse live imaging

KEY MESSAGE

Polarized auxin transport regulates fruit shape determination by promoting anisotropic cell growth. Angiosperms produce organs with distinct shape resultant from adaptive evolution. Understanding the cellular basis underlying the development of plant organ has been a central topic in plant biology as it is key to unlock the mechanisms leading to the diversification of plants. Variations in the location of synthesis, polarized auxin transport (PAT) have been proposed to account for the development of diverse organ shapes, but the exact cellular mechanism has yet to be elucidated. The Capsella rubella develops a perfect heart-shaped fruit from an ovate shape gynoecium that is tightly linked to the localized auxin synthesis in the valve tips and provides a unique opportunity to address this question. In this study, we studied auxin movement in the fruits and the cellular effect of N-1-Naphthylphthalamic Acid (NPA) on the fruit shape determination by constructing the pCrPIN3:PIN3:GFP reporter and live-imaging. We found PAT in the valve epidermis is in congruent with fruit shape development and NPA treatment disrupts the heat-shaped fruit development mainly by repressing cell anisotropic growth with minor effect on division. As the Capsella fruit is unusually big in size, we also included a detailed step-by-step protocol on how to conduct live-imaging experiment. We further test the utility of this protocol by conducting a live-imaging analysis of the gynophore in Arachis hypogaea. Collectively, the results of this study elucidated the mechanism on how auxin signal was translated into instructions guiding cell growth during organ shape determination. In addition, the description of the detailed live-imaging protocol will encourage further studies of the cellular mechanisms underlying shape diversification in angiosperms.

Review: Application of Bionic-Structured Materials in Solid-State Electrolytes for High-Performance Lithium Metal Batteries

Solid-state lithium metal batteries (SSLMBs) have gained significant attention in energy storage research due to their high energy density and significantly improved safety. But there are still certain problems with lithium dendrite growth, interface stability, and room-temperature practicality. Nature continually inspires human development and intricate design strategies to achieve optimal structural applications. Innovative solid-state electrolytes (SSEs), inspired by diverse natural species, have demonstrated exceptional physical, chemical, and mechanical properties. This review provides an overview of typical bionic-structured materials in SSEs, particularly those mimicking plant and animal structures, with a focus on their latest advancements in applications of solid-state lithium metal batteries. Commencing from plant structures encompassing roots, trunks, leaves, flowers, fruits, and cellular levels, the detailed influence of biomimetic strategies on SSE design and electrochemical performance are presented in this review. Subsequently, the recent progress of animal-inspired nanostructures in SSEs is summarized, including layered structures, surface morphologies, and interface compatibility in both two-dimensional (2D) and three-dimensional (3D) aspects. Finally, we also evaluate the current challenges and provide a concise outlook on future research directions. We anticipate that the review will provide useful information for future reference regarding the design of bionic-structured materials in SSEs.

Gynoecium and fruit development in Arabidopsis

Flowering plants produce flowers and one of the most complex floral structures is the pistil or the gynoecium. All the floral organs differentiate from the floral meristem. Various reviews exist on molecular mechanisms controlling reproductive development, but most focus on a short time window and there has been no recent review on the complete developmental time frame of gynoecium and fruit formation. Here, we highlight recent discoveries, including the players, interactions and mechanisms that govern gynoecium and fruit development in Arabidopsis. We also present the currently known gene regulatory networks from gynoecium initiation until fruit maturation.

An optimized protocol to assess SUMOylation in the plant Capsella rubella using two-component DEX-inducible transformants

Here, we present an efficient protocol to test the SUMOylation of a target protein in the plant Capsella rubella based on overexpression of dexamethasone (DEX)-inducible tagged proteins. We describe the construction of two-component, FLAG-tagged DEX-inducible plasmids. We then detail the transformation of Capsella, followed by DEX treatment and SUMOylation assays. This protocol can be widely applied to proteins with expression restricted to specific cells and tissues using native promoters as well as proteins whose overexpression leads to embryo lethality.

For complete details on the use and execution of this profile, please refer to Dong et al. (2020).

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An easy-to-use pipeline for constructing FLAG-tagged DEX-inducible plasmids

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An efficient transformation protocol for Capsella rubella

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An optimized protocol to test SUMOylation of a protein of interest in plants

Live-imaging provides an atlas of cellular growth dynamics in the stamen

Development of multicellular organisms is a complex process involving precise coordination of growth among individual cells. Understanding organogenesis requires measurements of cellular behaviors over space and time. In plants, such a quantitative approach has been successfully used to dissect organ development in both leaves and external floral organs, such as sepals. However, the observation of floral reproductive organs is hampered as they develop inside tightly closed floral buds, and are therefore difficult to access for imaging. We developed a confocal time-lapse imaging method, applied here to Arabidopsis (Arabidopsis thaliana), which allows full quantitative characterization of the development of stamens, the male reproductive organs. Our lineage tracing reveals the early specification of the filament and the anther. Formation of the anther lobes is associated with a temporal increase of growth at the lobe surface that correlates with intensive growth of the developing locule. Filament development is very dynamic and passes through three distinct phases: (1) initial intense, anisotropic growth, and high cell proliferation; (2) restriction of growth and proliferation to the filament proximal region; and (3) resumption of intense and anisotropic growth, displaced to the distal portion of the filament, without cell proliferation. This quantitative atlas of cellular growth dynamics provides a solid framework for future studies into stamen development.