Several species of fungi from the orders Chaetothyriales and Pleosporales have been reported to produce swainsonine and be associated as symbionts with plants of the Convolvulaceae and Fabaceae, respectively. An endosymbiont belonging to the Chaetothyriales produces swainsonine and grows as an epibiont on the adaxial leaf surfaces of Ipomoea carnea, but how the symbiont passes through plant growth and development is unknown. Herein, different types of microscopy were used to localize the symbiont in seeds and in cross sections of plant parts. The symbiont was found in several tissues including the hilum, the sclereids, and the hypocotyl of seeds. In five-day old seedlings and mature plants, the symbiont was found in the shoot apical meristem (SAM) and the adaxial surface of immature folded leaves. The mycelia generally formed a close association with peltate glandular trichomes. This report provides further data explaining the relationship between the seed transmitted Chaetothyriales symbiont and Ipomoea carnea. These results provide a possible explanation for how this symbiont, and others like Periglandula may persist and are transmitted over time.
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The Shoot Apical Meristem: A Tree’s Best Bud
Every spring, something seemingly miraculous happens in the woods in certain parts of the world—thousands of leaves burst from buds on bare tree branches, transforming the landscape from the browns and grays of winter to the bright greens of spring and summer. Although this process is most obvious in regions with drastic seasonal changes, seed plants all over the world regularly produce and lose leaves as they grow. How does this happen? Where do these leaves come from? The cells that make up these leaves are produced by a tiny cluster of cells called the shoot apical meristem. The cells in the shoot apical meristem have the potential to develop into various kinds of cells. Through cell division, meristem cells eventually produce all the above-ground parts of a plant, including leaves. In this article, we explain how meristems function and highlight how these tiny clusters of cells impact our day-to-day lives. We will also provide suggestions for observing meristems at work.
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- Award ID(s):
- 1652380
- NSF-PAR ID:
- 10410520
- Date Published:
- Journal Name:
- Frontiers for Young Minds
- Volume:
- 11
- ISSN:
- 2296-6846
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Land plants develop highly diversified shoot architectures, all of which are derived from the pluripotent stem cells in shoot apical meristems (SAMs). As sustainable resources for continuous organ formation in the aboveground tissues, SAMs play an important role in determining plant yield and biomass production. In this review, we summarize recent advances in understanding one group of key regulators – the HAIRY MERISTEM (HAM) family GRAS domain proteins – in shoot meristems. We highlight the functions of HAM family members in dictating shoot stem cell initiation and proliferation, the signaling cascade that shapes HAM expression domains in shoot meristems, and the conservation and diversification of HAM family members in land plants. We also discuss future directions that potentially lead to a more comprehensive view of the HAM gene family and stem cell homeostasis in land plants.more » « less
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Organ initiation from the shoot apical meristem first gives rise to leaves during vegetative development and then flowers during reproductive development.
LEAFY (LFY ) is activated after floral induction and together with other factors promotes the floral program. LFY functions redundantly with APETALA1 (AP1) to activate the class B genesAPETALA3 (AP3 ) andPISTILLATA (PI ), the class C geneAGAMOUS (AG ), and the class E geneSEPALLATA3 , which leads to the specification of stamens and carpels, the reproductive organs of flowers. Molecular and genetic networks that control the activation ofAP3, PI, andAG in flowers have been well studied; however, much less is known about how these genes are repressed in leaves and how their repression is lifted in flowers. Here, we showed that two genes encodingArabidopsis C2H2 ZINC FINGER PROTEIN (ZFP) transcription factors, ZP1 and ZFP8, act redundantly to directly repressAP3, PI, andAG in leaves. AfterLFY andAP1 are activated in floral meristems, they down-regulateZP1 andZFP8 directly to lift the repression onAP3, PI, andAG . Our results reveal a mechanism for how floral homeotic genes are repressed and derepressed before and after floral induction. -
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Abstract Grass leaves develop from a ring of primordial initial cells within the periphery of the shoot apical meristem, a pool of organogenic stem cells that generates all of the organs of the plant shoot. At maturity, the grass leaf is a flattened, strap-like organ comprising a proximal supportive sheath surrounding the stem and a distal photosynthetic blade. The sheath and blade are partitioned by a hinge-like auricle and the ligule, a fringe of epidermally derived tissue that grows from the adaxial (top) leaf surface. Together, the ligule and auricle comprise morphological novelties that are specific to grass leaves. Understanding how the planar outgrowth of grass leaves and their adjoining ligules is genetically controlled can yield insight into their evolutionary origins. Here we use single-cell RNA-sequencing analyses to identify a ‘rim’ cell type present at the margins of maize leaf primordia. Cells in the leaf rim have a distinctive identity and share transcriptional signatures with proliferating ligule cells, suggesting that a shared developmental genetic programme patterns both leaves and ligules. Moreover, we show that rim function is regulated by genetically redundant Wuschel-like homeobox3 (WOX3) transcription factors. Higher-order mutations in maize
Wox3 genes greatly reduce leaf width and disrupt ligule outgrowth and patterning. Together, these findings illustrate the generalizable use of a rim domain during planar growth of maize leaves and ligules, and suggest a parsimonious model for the homology of the grass ligule as a distal extension of the leaf sheath margin. -
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SUMMARY In contrast to seed plants, the gametophytes of seed‐free plants develop pluripotent meristems, which promote and sustain their independent growth and development. To date, the cellular basis of meristem development in gametophytes of seed‐free ferns remains largely unknown. In this study, we used
Woodsia obtusa , the blunt‐lobe cliff fern, to quantitatively determine cell growth dynamics in two different types of apical meristems – the apical initial centered meristem and the multicellular apical meristem in gametophytes. Through confocal time‐lapse live imaging and computational image analysis and quantification, we determined unique patterns of cell division and growth that sustain or terminate apical initials, dictate the transition from apical initials to multicellular apical meristems, and drive proliferation of apical meristems in ferns. Quantitative results showed that small cells correlated to active cell division in fern gametophytes. The marginal cells of multicellular apical meristems in fern gametophytes undergo division in both anticlinal and periclinal orientations, not only increasing cell numbers but also playing a dominant role in increasing cell layers during gametophyte development. All these findings provide insights into the function and regulation of meristems in gametophytes of seed‐free vascular plants, suggesting both conserved and diversified mechanisms underlying meristem cell proliferation across land plants.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/frym.2023.965617
