Comparison of Promeristem Structure and Ontogeny of Procambium in Primary Roots of Zea mays ssp. Mexicana and Z. mays ‘Honey Bantam’ with Emphasis on Metaxylem Vessel Histogenesis

Classical histology describes the histological organization in Zea mays as having a “closed organization” that differs from Arabidopsis with the development of xylem conforming to predictable rules. We speculated that root apical meristem organization in a wild subspecies of Z. mays (a teosinte) would differ from a domestic sweetcorn cultivar (‘Honey Bantam’). Careful comparison could contribute to understanding how evolutionary processes and the domestication of maize have affected root development. Root tips of seedlings were prepared and sectioned for light microscopy. Most sections were treated with RNase before staining to increase contrast between the walls and cytoplasm. Longitudinal and serial transverse sections were analyzed using computer imaging to determine the position and timing of key xylem developmental events. Metaxylem development in mexicana teosinte differed from sweetcorn only in that the numbers of late-maturing metaxylem vessels in the latter are typically two-fold greater and the number of cells in the transverse section of procambium were greater in the latter, but parenchymatous cell sizes were not statistically different. Promeristems of both were nearly identical in size and organization, but did not operate quite as previously described. Mitotic activity was rare in the quiescent centers, but occasionally a synchronized pulse of mitoses was observed there. Our reinterpretation of histogen theory and procambium development should be useful for future detailed studies of regulation of development, and perhaps its evolution, in this species.

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Evaluation of Metaxylem Vessel Histogenesis and the Occurrence of Vessel Collapse during Early Development in Primary Roots of Zea mays ssp. mexicana: A Result of Premature Programmed Cell Death?

Plants ◽

10.3390/plants9030374 ◽

2020 ◽

Vol 9 (3) ◽

pp. 374

Author(s):

Susumu Saito ◽

Teruo Niki ◽

Daniel K. Gladish

Keyword(s):

Cell Death ◽

Zea Mays ◽

Programmed Cell Death ◽

Primary Root ◽

Cell Types ◽

Root Apical Meristem ◽

Root Tips ◽

Primary Roots ◽

Transmission Electron ◽

Vessel Elements

Root apical meristem histological organization in Zea mays has been carefully studied previously. Classical histology describes its system as having a “closed organization” and a development of xylem that conforms to predictable rules. Among the first cell types to begin differentiation are late-maturing metaxylem (LMX) vessels. As part of a larger study comparing domestic maize root development to a wild subspecies of Z. mays (teosinte), we encountered a metaxylem development abnormality in a small percentage of our specimens that begged further study, as it interrupted normal maturation of LMX. Primary root tips of young seedlings of Zea mays ssp. mexicana were fixed, embedded in appropriate resins, and sectioned for light and transmission electron microscopy. Longitudinal and serial transverse sections were analyzed using computer imaging to determine the position and timing of key xylem developmental events. We observed a severe abnormality of LMX development among 3.5% of the 227 mexicana seedlings we screened. All LMX vessel elements in these abnormal roots collapsed and probably became non-functional shortly after differentiation began. Cytoplasm and nucleoplasm in the abnormal LMX elements became condensed and subdivided into irregularly-shaped “macrovesicles” as their cell walls collapsed inward. We propose that these seedlings possibly suffered from a mutation that affected the timing of the programmed cell death (PCD) that is required to produce functional xylem vessels, such that autolysis of the cytoplasm was prematurely executed, i.e., prior to the development and lignification of secondary walls.

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The microtubule-associated protein CLASP is translationally-regulated in light-dependent root apical meristem growth

10.1101/2020.04.20.051417 ◽

2020 ◽

Author(s):

Laryssa Halat ◽

Katherine Gyte ◽

Geoffrey Wasteneys

Keyword(s):

Root Growth ◽

Apical Meristem ◽

Root Meristem ◽

Growth Promotion ◽

Root Apical Meristem ◽

Root Tips ◽

Protein Levels ◽

Hormone Transport ◽

Dividing Cells ◽

Root Growth Promotion

ABSTRACTThe ability for plant growth to be optimized, either in the light or dark, depends on the intricate balance between cell division and differentiation in specialized regions called meristems. When Arabidopsis thaliana seedlings are grown in the dark, hypocotyl elongation is promoted, whereas root growth is greatly reduced as a result of changes in hormone transport and a reduction in meristematic cell proliferation. Previous work showed that the microtubule-associated protein CLASP sustains root apical meristem (RAM) size by influencing microtubule (MT) organization and by modulating the brassinosteroid (BR) signalling pathway. Here, we investigated whether CLASP is involved in light-dependent root growth promotion, since dark-grown seedlings have reduced RAM activity that is observed in the clasp-1 null mutant. We showed that CLASP protein levels were greatly reduced in the root tips of dark-grown seedlings, which could be reversed by exposing plants to light. We confirmed that removing seedlings from the light led to a discernible shift in MT organization from bundled arrays, which are prominent in dividing cells, to transverse orientations typically observed in cells that have exited the meristem. BR receptors and auxin transporters, both of which are sustained by CLASP, were largely degraded in the dark. Interestingly, we found that despite the lack of protein, CLASP transcript levels were higher in dark-grown root tips. Together, these findings uncover a mechanism that sustains meristem homeostasis through CLASP, and advances our understanding of how roots modulate their growth according to the amount of light and nutrients perceived by the plant.One Sentence SummaryThe microtubule-associated protein CLASP is regulated at the translational level when root meristem growth is inhibited in dark-grown plants.

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Anchorene is an endogenous diapocarotenoid required for anchor root formation in Arabidopsis

10.1101/496737 ◽

2018 ◽

Cited By ~ 3

Author(s):

Kun-Peng Jia ◽

Alexandra J. Dickinson ◽

Jianing Mi ◽

Guoxin Cui ◽

Najeh M. Kharbatia ◽

...

Keyword(s):

Root Development ◽

Apical Meristem ◽

Root Formation ◽

Carotenoid Biosynthesis ◽

Root Apical Meristem ◽

Arabidopsis Root ◽

Auxin Homeostasis ◽

Chemical Inhibitors ◽

The Family ◽

Natural Metabolite

AbstractArabidopsis root development is predicted to be regulated by yet unidentified carotenoid-derived metabolite(s). In this work, we screened known and putative carotenoid cleavage products and identified anchorene, a predicted carotenoid-derived dialdehyde (diapocarotenoid) that triggers anchor root development. Anchor roots are the least characterized type of root in Arabidopsis. They form at the root-shoot junction, particularly upon damage to the root apical meristem. Using Arabidopsis reporter lines, mutants and chemical inhibitors, we show that anchor roots originate from pericycle cells and that the development of this root type is auxin-dependent and requires carotenoid biosynthesis. Transcriptome analysis and treatment of auxin-reporter lines indicate that anchorene triggers anchor root development by modulating auxin homeostasis. Exogenous application of anchorene restored anchor root development in carotenoid-deficient plants, indicating that this compound is the carotenoid-derived signal required for anchor root development. Chemical modifications of anchorene led to a loss of anchor root promoting activity, suggesting that this compound is highly specific. Furthermore, we demonstrate by LC-MS analysis that anchorene is a natural, endogenous Arabidopsis metabolite. Taken together, our work reveals a new member of the family of carotenoid-derived regulatory metabolites and hormones.SignificanceUnknown carotenoid-derived compounds are predicted to regulate different aspects of plant development. Here, we characterize the development of anchor roots, the least characterized root type in Arabidopsis, and show that this process depends on auxin and requires a carotenoid-derived metabolite. We identified a presumed carotenoid-derivative, anchorene, as the likely, specific signal involved in anchor root formation. We further show that anchorene is a natural metabolite that occurs in Arabidopsis. Based on the analysis of auxin reporter lines and transcriptome data, we provide evidence that anchorene triggers the growth of anchor roots by modulating auxin homeostasis. Taken together, our work identifies a novel carotenoid-derived growth regulator with a specific developmental function.

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The Medicago truncatula nodule identity gene MtNOOT1 is required for coordinated apical-basal development of the root

BMC Plant Biology ◽

10.1186/s12870-019-2194-z ◽

2019 ◽

Vol 19 (1) ◽

Cited By ~ 1

Author(s):

Defeng Shen ◽

Olga Kulikova ◽

Kerstin Guhl ◽

Henk Franssen ◽

Wouter Kohlen ◽

...

Keyword(s):

Cell Differentiation ◽

Medicago Truncatula ◽

Root Development ◽

Lateral Root ◽

Apical Meristem ◽

Spatial Development ◽

Root Apical Meristem ◽

Nodule Development ◽

Lateral Root Development ◽

Xylem Cell

Abstract Background Legumes can utilize atmospheric nitrogen by hosting nitrogen-fixing bacteria in special lateral root organs, called nodules. Legume nodules have a unique ontology, despite similarities in the gene networks controlling nodule and lateral root development. It has been shown that Medicago truncatula NODULE ROOT1 (MtNOOT1) is required for the maintenance of nodule identity, preventing the conversion to lateral root development. MtNOOT1 and its orthologs in other plant species -collectively called the NOOT-BOP-COCH-LIKE (NBCL) family- specify boundary formation in various aerial organs. However, MtNOOT1 is not only expressed in nodules and aerial organs, but also in developing roots, where its function remains elusive. Results We show that Mtnoot1 mutant seedlings display accelerated root elongation due to an enlarged root apical meristem. Also, Mtnoot1 mutant roots are thinner than wild-type and are delayed in xylem cell differentiation. We provide molecular evidence that the affected spatial development of Mtnoot1 mutant roots correlates with delayed induction of genes involved in xylem cell differentiation. This coincides with a basipetal shift of the root zone that is susceptible to rhizobium-secreted symbiotic signal molecules. Conclusions Our data show that MtNOOT1 regulates the size of the root apical meristem and vascular differentiation. Our data demonstrate that MtNOOT1 not only functions as a homeotic gene in nodule development but also coordinates the spatial development of the root.

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Redox regulation of root apical meristem organization: Connecting root development to its environment

Plant Physiology and Biochemistry ◽

10.1016/j.plaphy.2009.11.005 ◽

2010 ◽

Vol 48 (5) ◽

pp. 328-336 ◽

Cited By ~ 87

Author(s):

Mario C. De Tullio ◽

Keni Jiang ◽

Lewis J. Feldman

Keyword(s):

Root Development ◽

Apical Meristem ◽

Redox Regulation ◽

Root Apical Meristem

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Critical level of radiation damage of root apical meristem and mechanisms for its recovery in Pisum sativum L.

Cytology and Genetics ◽

10.3103/s0095452711010051 ◽

2011 ◽

Vol 45 (1) ◽

pp. 18-26 ◽

Cited By ~ 2

Author(s):

E. A. Kravets ◽

A. N. Mikheev ◽

L. G. Ovsyannikova ◽

D. M. Grodzinsky

Keyword(s):

Pisum Sativum ◽

Radiation Damage ◽

Apical Meristem ◽

Critical Level ◽

Root Apical Meristem ◽

Pisum Sativum L

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Sound Waves Promote Arabidopsis thaliana Root Growth by Regulating Root Phytohormone Content

International Journal of Molecular Sciences ◽

10.3390/ijms22115739 ◽

2021 ◽

Vol 22 (11) ◽

pp. 5739

Author(s):

Joo Yeol Kim ◽

Hyo-Jun Lee ◽

Jin A Kim ◽

Mi-Jeong Jeong

Keyword(s):

Arabidopsis Thaliana ◽

Cell Division ◽

Root Growth ◽

Apical Meristem ◽

Cell Number ◽

Root Apical Meristem ◽

Control Group ◽

Auxin Signaling ◽

Ethylene Signaling ◽

Sound Waves

Sound waves affect plants at the biochemical, physical, and genetic levels. However, the mechanisms by which plants respond to sound waves are largely unknown. Therefore, the aim of this study was to examine the effect of sound waves on Arabidopsis thaliana growth. The results of the study showed that Arabidopsis seeds exposed to sound waves (100 and 100 + 9k Hz) for 15 h per day for 3 day had significantly longer root growth than that in the control group. The root length and cell number in the root apical meristem were significantly affected by sound waves. Furthermore, genes involved in cell division were upregulated in seedlings exposed to sound waves. Root development was affected by the concentration and activity of some phytohormones, including cytokinin and auxin. Analysis of the expression levels of genes regulating cytokinin and auxin biosynthesis and signaling showed that cytokinin and ethylene signaling genes were downregulated, while auxin signaling and biosynthesis genes were upregulated in Arabidopsis exposed to sound waves. Additionally, the cytokinin and auxin concentrations of the roots of Arabidopsis plants increased and decreased, respectively, after exposure to sound waves. Our findings suggest that sound waves are potential agricultural tools for improving crop growth performance.

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Early Pinus caribaea var. hondurensis root development. 2. Influence of soil strength

Australian Journal of Experimental Agriculture ◽

10.1071/ea9960847 ◽

1996 ◽

Vol 36 (7) ◽

pp. 847 ◽

Cited By ~ 8

Author(s):

A Costantini ◽

D Doley ◽

HB So

Keyword(s):

Root Development ◽

Soil Type ◽

Root Elongation ◽

Primary Root ◽

High Strength ◽

Soil Strength ◽

Shoot Development ◽

Pinus Caribaea ◽

Primary Shoot ◽

Primary Roots

The influence of penetration resistance (PR), an easily measured indicator of soil strength, on the growth of Pinus caribaea var. hondurensis radicles and seedlings was investigated. Negative exponential relationships between PR and both radicle and primary root elongation were observed. All root elongation ceased at PR levels of 3.25 MPa. Tip diameters of radicles and primary roots were positively correlated with PR values up to 2.4 MPa, whilst numbers of primary roots, total root lengths and lengths of longest roots were all negatively correlated with PR. Hypocotyl elongation was also reduced by increasing PR, although the reductions occurred at higher PRs than those which inhibited root development. In contrast, primary shoot development was unaffected by PR levels which were sufficient to stop root elongation, but was reduced in soil with a PR of 4.8 MPa. There were significant family x soil type and family x PR interactions for radicle, hypocotyl, primary root and primary shoot development. 1f these interactions are correlated with performance in the field, then they may serve as useful indicators of family suitability to both soil type and high strength soils.

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