Early sensing of phosphate deprivation triggers the formation of extra root cap cell layers via SOMBRERO through a process antagonized by auxin signaling

Short tandem target mimic (STTM), which is composed of two short sequences mimicking small RNA target sites, separated by a linker of optimal size, can block the functions of all members in a miRNA family. microRNA393 (miR393), which is one of the conserved miRNA families in plants, can regulate plant root growth, leaf development, plant architecture, and stress resistance. In order to verify the role of miR393 in the secondary growth of trees, we created its STTM transgenic poplar lines (STTM393). The expression of miR393 in STTM393 lines was reduced by over 10 times compared with the control plants. STTM393 lines showed promoted growth with about 20% higher, 15% thicker, and 2–4 more internodes than the control plants after 3 months of growth. The cross-section of the stems showed that STTM393 lines had wider phloem, xylem, and more cambium cell layers than control plants, and the lignin content in STTM393 lines was also higher as revealed by staining and chemical determination. Based on the transcriptome analysis, the genes related to the auxin signaling pathway, cell cyclin, cell expansion, and lignin synthesis had higher expression in STTM393 lines than that in control plants. The higher expression levels of FBL family members suggested that the auxin signaling pathway was strengthened in STTM393 lines to promote plant growth. Therefore, the knockdown of miR393 using the STTM approach provides a way to improve poplar growth and biomass production.

Download Full-text

The cap size and shape of Arabidopsis thaliana primary roots impact the root responses to an increase in medium strength

10.1101/378828 ◽

2018 ◽

Author(s):

J. Roué ◽

H. Chauvet ◽

N. Brunel-Michac ◽

F. Bizet ◽

B. Moulia ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Primary Root ◽

Root Cap ◽

Size And Shape ◽

Primary Roots ◽

Medium Strength ◽

Cell Layers ◽

Root Responses ◽

Mutant Lines

AbstractDuring root progression in soil, root cap cells are the first to encounter obstacles. The root cap is known to sense environmental cues, making it a relevant candidate for a mechanosensing site. An original two-layer medium was developed in order to study root responses to growth medium strength and the importance of the root cap in the establishment of these responses. Root growth and trajectory of primary roots of Arabidopsis thaliana seedlings were investigated using in vivo image analysis. After contact with the harder layer, the root either penetrated it or underwent rapid curvature, enabling reorientation of the root primary growth. The role of the root cap in tip reorientation was investigated by analyzing the responses of Arabidopsis mutant roots with altered caps. The primary root of fez-2 mutant lines, which has fewer root cap cell layers than wild-type roots, showed impaired penetration ability. Conversely, smb-3 roots of mutant lines, which display a higher number of root cap cells, showed enhanced penetration abilities. This work highlights that alterations in root cap shape and size affect the root responses to medium strength.HighlightThe analysis of the growth and orientation of Arabidopsis thaliana mutant roots affected in root cap size and shape showed that properly formed root cap is required to trigger the root responses to medium strength.AbbreviationsCOLcolumella;LRCLateral Root Cap;SISharpness Index;SMBSOMBRERO.

Download Full-text

Activation of rape (Brassica napus L.) embryo during seed germination. IV. Germinating embryo. The first zones of mitoses, starch and DNA synthesis and their expansion pattern

Acta Societatis Botanicorum Poloniae ◽

10.5586/asbp.1986.045 ◽

2014 ◽

Vol 55 (4) ◽

pp. 539-563 ◽

Cited By ~ 6

Author(s):

Mieczysław Kuraś

Keyword(s):

Dna Synthesis ◽

Cell Activation ◽

Starch Synthesis ◽

Lower Boundary ◽

Apical Part ◽

Cell Number ◽

Root Cap ◽

Brassica Napus L ◽

Cell Divisions ◽

Cell Layers

The rape radicle is completely covered by the root cap. The successive lateral cell layers of the root cap are terminated by T-forming walls in the dermatogen layer in a statistically constant position. T-walls in dermatogen were utilized for delimitation of successive root sectors on longitudinal microtome sections at the succeeding germination stages. The length and the cell number of the corresponding sectors were studied and the starch and DNA synthesis sites as well as cell divisions localized. All these processes are initiated in a constant sequence and in specific embryo zones. The first symptom of activation of the embryo is starch synthesis. It begins in two centres: in the apical part of the radicle columella and in the hypoctyl dermalogen it moves deep into the cortex and in both directions along the columella the activation of starch synthesis shifts basipetally into the whole columella and the initial centre as well as the lateral parts of the root cap. From the hypocotyl dermatogen it moves into the cortex and in both directions along the embryo axis. In the root dermatogen and periblem the activation zone is first located in the basal sector and, then, gradually, in the lower ones. Just before germination the basal and apical zones of activation meet. Starch can then, be found throughout the root. During starch synthesis, in the basal part of the radicle. DNA synthesis and cell growth begin. In the root sectors which have already begun to grow and synthesize DNA, cell divisions start. The boundary of the dividing cells zone shifts acropetally at some distance above the lower boundary of DNA synthesis and the zone of cell premitotic growth. The acropetal shift of the mitotic activation zones can be described as wave expansion. Before the first mitotic wave reaches the promeristem it is followed by at least three acropetal waves, arising in the already activated basal sectors. and then the mitoses are asynchronised. Mitotic.: activation of the root cap is partly independent of the acropetal wave of cell activation and results from the expanding weaker basipetal wave.

Download Full-text

The effect of colonization by Verticillium dahliae on the root tips of Russet Burbank potatoes

Canadian Journal of Botany ◽

10.1139/b83-385 ◽

1983 ◽

Vol 61 (12) ◽

pp. 3422-3429 ◽

Cited By ~ 25

Author(s):

James W. Perry ◽

Ray F. Evert

Keyword(s):

Verticillium Dahliae ◽

Apical Meristem ◽

Solanum Tuberosum L ◽

Root Cap ◽

Root Tips ◽

Vascular Differentiation ◽

Infected Root ◽

Cell Layers ◽

Wall Appositions ◽

Verticillium Dahliae Kleb

The structure and development of tissues in potato (Solanum tuberosum L.) root tips colonized by Verticillium dahliae Kleb. were contrasted with those of uninoculated root tips. Within 2 days of inoculation hyphae had penetrated the root cap without eliciting any wall appositions in the root cap cells. Callose-like deposits were found along the walls of protodermal cells bordering the colonized cap cells. Overall, colonized root tips had lost their meristematic appearance owing to increased vacuolation in the cells. In contrast to the normal longitudinal course of primary vascular differentiation, in infected root tips the protoxylem matured in advance of the protophloem. Fifteen days after inoculation the root tips had lapsed into maturity. The endodermis and exodermis extended completely around what was once the apical meristem. Although the xylem had differentiated to within several cell layers of the colonized apex, xylem infection had not occurred in this region. Sieve elements in colonized root tips failed to develop sieve-plate pores.

Download Full-text

Tornado1 and tornado2 are required for the specification of radial and circumferential pattern in the Arabidopsis root

Development ◽

10.1242/dev.127.15.3385 ◽

2000 ◽

Vol 127 (15) ◽

pp. 3385-3394

Author(s):

G. Cnops ◽

X. Wang ◽

P. Linstead ◽

M. Van Montagu ◽

M. Van Lijsebettens ◽

...

Keyword(s):

Root Hair ◽

Lateral Root ◽

Cell Function ◽

Primary Root ◽

Root Cap ◽

Radial Pattern ◽

Root Hair Cell ◽

Cell Layers ◽

Default State ◽

Hair Cell Differentiation

The cell layers of the Arabidopsis primary root are arranged in a simple radial pattern. The outermost layer is the lateral root cap and lies outside the epidermis that surrounds the ground tissue. The files of epidermal and lateral root cap cells converge on a ring of initials (lateral root cap/epidermis initial) from which the epidermal and lateral root cap tissues of the seedling are derived, once root growth is initiated after germination. Each initial gives rise to a clone of epidermal cells and a clone of lateral root cap cells. These initial divisions in the epidermal/lateral root cap initial are defective in tornado1 (trn1) and trn2 plants indicating a requirement for TRN1 and TRN2 for initial cell function. Furthermore, lateral root cap cells develop in the epidermal position in trn1 and trn2 roots indicating that TRN1 and TRN2 are required for the maintenance of the radial pattern of cell specification in the root. The death of these ectopic lateral root cap cells in the elongation zone (where lateral root cap cells normally die) results in the development of gaps in the epidermis. These observations indicate that TRN1 and TRN2 are required to maintain the distinction between the lateral root cap and epidermis and suggest that lateral root cap fate is the default state. It also suggests that TRN1 and TRN2 repress lateral root cap fate in cells in the epidermal location. Furthermore, the position-dependent pattern of root hair and non-root hair cell differentiation in the epidermis is defective in trn1 and trn2 mutants. Together these results indicate that TRN1 and TRN2 are required for the maintenance of both the radial pattern of tissue differentiation in the root and for the subsequent circumferential pattern within the epidermis.

Download Full-text

The Ultrastructure of Monkey Gingival Epithelium

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010006009x ◽

1967 ◽

Vol 25 ◽

pp. 16-17

Author(s):

C.N. Sun

Keyword(s):

Epithelial Cells ◽

Macaca Nemestrina ◽

Stratum Granulosum ◽

Solution Ph ◽

Gingival Epithelial Cells ◽

Stratum Spinosum ◽

Cell Layers ◽

Gingival Epithelium ◽

The Individual ◽

Different Thickness

The present study demonstrates the ultrastructure of the gingival epithelium of the pig tail monkey (Macaca nemestrina). Specimens were taken from lingual and facial gingival surfaces and fixed in Dalton's chrome osmium solution (pH 7.6) for 1 hr, dehydrated, and then embedded in Epon 812.Tonofibrils are variable in number and structure according to the different region or location of the gingival epithelial cells, the main orientation of which is parallel to the long axis of the cells. The cytoplasm of the basal epithelial cells contains a great number of tonofilaments and numerous mitochondria. The basement membrane is 300 to 400 A thick. In the cells of stratum spinosum, the tonofibrils are densely packed and increased in number (fig. 1 and 3). They seem to take on a somewhat concentric arrangement around the nucleus. The filaments may occur scattered as thin fibrils in the cytoplasm or they may be arranged in bundles of different thickness. The filaments have a diameter about 50 A. In the stratum granulosum, the cells gradually become flatted, the tonofibrils are usually thin, and the individual tonofilaments are clearly distinguishable (fig. 2). The mitochondria and endoplasmic reticulum are seldom seen in these superficial cell layers.

Download Full-text

Localization of acid phosphatases in root cap of rice plant

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100085423 ◽

1991 ◽

Vol 49 ◽

pp. 224-225

Author(s):

Y. R. Chen ◽

Y. F. Huang ◽

W. S. Chen

Keyword(s):

Rice Plant ◽

Developmental Stages ◽

Uranyl Acetate ◽

Root Cap ◽

Plant Tissues ◽

Acid Phosphatases ◽

Root Tips ◽

Buffer Solution ◽

Cacodylate Buffer ◽

Ethanol Series

Acid phosphatases are widely distributed in different tisssues of various plants. Studies on subcellular localization of acid phosphatases show they might be present in cell wall, plasma lemma, mitochondria, plastid, vacuole and nucleus. However, their localization in rice cell varies with developmental stages of cells and plant tissues. In present study, acid phosphatases occurring in root cap are examined.Sliced root tips of ten-day-old rice(Oryza sativa) seedlings were fixed in 0.1M cacodylate buffer containing 2.5% glutaraldehyde for 2h, washed overnight in same buffer solution, incubated in Gomori's solution at 37° C for 90min, post-fixed in OsO4, dehydrated in ethanol series and finally embeded in Spurr's resin. Sections were doubly stained with uranyl acetate and lead citrate, and observed under Hitachi H-600 at 75 KV.

Download Full-text