Rhizobial Nod factors are required for cortical cell division in the nodule morphogenetic programme of the Aeschynomeneae legume Arachis

Nod factors secreted by Rhizobium leguminosarum bv. viciae induce root hair deformation, involving a reinitiation of tip growth, and the formation of nodule primordia in Vicia sativa (vetch). Ethylene is a potent inhibitor of cortical cell division, an effect that can be counteracted by applying silver ions (Ag+) or aminoethoxy-vinylglycine (AVG). In contrast to the inhibitory effect on cortical cell division, ethylene promotes the formation of root hairs (which involves tip growth) in the root epidermis of Arabidopsis. We investigate the possible paradox concerning the action of ethylene, putatively promoting Nod factor induced tip growth whilst, at the same time, inhibiting cortical cell division. We show, by using the ethylene inhibitors AVG and Ag+, that ethylene has no role in the reinitiation of root hair tip growth induced by Nod factors (root hair deformation) in vetch. However, root hair formation is controlled, at least in part, by ethylene. Furthermore, we show that ACC oxidase, which catalizes the last step in ethylene biosynthesis, is expressed in the cell layers opposite the phloem in that part of the root where nodule primordia are induced upon inoculation with Rhizobium. Therefore, we test whether endogenously produced ethylene provides positional information controlling the site where nodule primordia are formed by determining the position of nodules formed on pea roots grown in the presence of AVG or Ag+.

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SHR–SCR regulates cortical cell division and nodulation

Molecular Plant ◽

10.1016/j.molp.2021.01.007 ◽

2021 ◽

Vol 14 (2) ◽

pp. 198

Author(s):

M. Arif Ashraf ◽

Jaimie M. Van Norman

Keyword(s):

Cell Division ◽

Cortical Cell

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Biological activity of Nod factors

Acta Biochimica Polonica ◽

10.18388/abp.2020_5353 ◽

2020 ◽

Author(s):

Dominika Kidaj ◽

Mikolaj Krysa ◽

Katarzyna Susniak ◽

Joanna Matys ◽

Iwona Komaniecka ◽

...

Keyword(s):

Molecular Level ◽

Root Nodules ◽

Cortical Cell ◽

Plant Tissues ◽

Nod Factors ◽

Nod Factor ◽

Expression Of Genes ◽

Root Hair Deformation ◽

Low Concentrations ◽

Genes Encoding

Chemically, the Nod factors (NFs) are lipochitooligosaccharides, produced mainly by bacteria of the Rhizobium genus. They are the main signaling molecules involved in the initiation of symbiosis between rhizobia and legume plants. Nod factors affect plant tissues at very low concentrations, even as low as 10–12 mol/L. They induce root hair deformation, cortical cell division, and root nodules’ formation in the host plant. At the molecular level, the cytoskeleton is reorganized and expression of genes encoding proteins called nodulins is induced in response to Nod factors in the cell. Action of Nod factors is highly specific because it depends on the structure of a particular Nod factor involved, as well as the plant receptor reacting with it.

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Chitin oligosaccharides can induce cortical cell division in roots of Vicia sativa when delivered by ballistic microtargeting

Current Opinion in Plant Biology ◽

10.1016/s1369-5266(98)80007-1 ◽

1998 ◽

Vol 1 (2) ◽

pp. 97-98

Keyword(s):

Cell Division ◽

Cortical Cell ◽

Vicia Sativa

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A model for the development of the rhizobial and arbuscular mycorrhizal symbioses in legumes and its use to understand the roles of ethylene in the establishment of these two symbioses

Canadian Journal of Botany ◽

10.1139/b02-066 ◽

2002 ◽

Vol 80 (7) ◽

pp. 695-720 ◽

Cited By ~ 110

Author(s):

F C Guinel ◽

R D Geil

Keyword(s):

Arbuscular Mycorrhizae ◽

Cell Layer ◽

Cortical Cell ◽

Arbuscular Mycorrhizal ◽

Nod Factors ◽

Pisum Sativum L ◽

Rhizobial Symbiosis ◽

Nodulation Mutants ◽

Sites Of Action ◽

Root Tissues

We propose a model depicting the development of nodulation and arbuscular mycorrhizae. Both processes are dissected into many steps, using Pisum sativum L. nodulation mutants as a guideline. For nodulation, we distinguish two main developmental programs, one epidermal and one cortical. Whereas Nod factors alone affect the cortical program, bacteria are required to trigger the epidermal events. We propose that the two programs of the rhizobial symbiosis evolved separately and that, over time, they came to function together. The distinction between these two programs does not exist for arbuscular mycorrhizae development despite events occurring in both root tissues. Mutations that affect both symbioses are restricted to the epidermal program. We propose here sites of action and potential roles for ethylene during the formation of the two symbioses with a specific hypothesis for nodule organogenesis. Assuming the epidermis does not make ethylene, the microsymbionts probably first encounter a regulatory level of ethylene at the epidermis outermost cortical cell layer interface. Depending on the hormone concentrations there, infection will either progress or be blocked. In the former case, ethylene affects the cortex cytoskeleton, allowing reorganization that facilitates infection; in the latter case, ethylene acts on several enzymes that interfere with infection thread growth, causing it to abort. Throughout this review, the difficulty of generalizing the roles of ethylene is emphasized and numerous examples are given to demonstrate the diversity that exists in plants.Key words: AM, epidermis, evolution, pea, rhizobia, sym mutant.

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SHORT-ROOT paralogs mediate feedforward regulation of D-type cyclin to promote nodule formation in soybean

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2108641119 ◽

2022 ◽

Vol 119 (3) ◽

pp. e2108641119

Author(s):

Chunhua Wang ◽

Meng Li ◽

Yang Zhao ◽

Nengsong Liang ◽

Haiyang Li ◽

...

Keyword(s):

Cell Division ◽

Vascular Tissue ◽

De Novo ◽

Cortical Cell ◽

Nodule Formation ◽

Cytokinin Signaling ◽

Short Root ◽

Cell Divisions ◽

Early Nodulin ◽

Nodulin Genes

Nitrogen fixation in soybean takes place in root nodules that arise from de novo cell divisions in the root cortex. Although several early nodulin genes have been identified, the mechanism behind the stimulation of cortical cell division during nodulation has not been fully resolved. Here we provide evidence that two paralogs of soybean SHORT-ROOT (GmSHR) play vital roles in soybean nodulation. Expression of GmSHR4 and GmSHR5 (GmSHR4/5) is induced in cortical cells at the beginning of nodulation, when the first cell divisions occur. The expression level of GmSHR4/5 is positively associated with cortical cell division and nodulation. Knockdown of GmSHR5 inhibits cell division in outer cortical layers during nodulation. Knockdown of both paralogs disrupts the cell division throughout the cortex, resulting in poorly organized nodule primordia with delayed vascular tissue formation. GmSHR4/5 function by enhancing cytokinin signaling and activating early nodulin genes. Interestingly, D-type cyclins act downstream of GmSHR4/5, and GmSHR4/5 form a feedforward loop regulating D-type cyclins. Overexpression of D-type cyclins in soybean roots also enhanced nodulation. Collectively, we conclude that the GmSHR4/5-mediated pathway represents a vital module that triggers cytokinin signaling and activates D-type cyclins during nodulation in soybean.

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Benzyladenine Effects on Cell Division and Cell Size during Apple Fruit Thinning

HortScience ◽

10.21273/hortsci.30.4.852f ◽

1995 ◽

Vol 30 (4) ◽

pp. 852F-852

Author(s):

Paul T. Wismer ◽

J.T.A. Proctor ◽

D.C. Elfving

Keyword(s):

Cell Division ◽

Cell Size ◽

Control Cell ◽

Fruit Size ◽

Cortical Cell ◽

Dry Weight ◽

Apple Fruit ◽

Naphthaleneacetic Acid ◽

Fruit Thinning ◽

Control Cell Division

Benzyladenine (BA), carbaryl (CB), daminozide (DM), and naphthaleneacetic acid (NAA) were applied postbloom, as fruitlet thinning agents, to mature `Empire' apple trees. Although fruit set and yield were similar for BA, NAA, and CB, BA-treated fruit were larger, indicating BA increased fruit size beyond the effect attributable to thinning. BA applied at 100 mg·liter–1 increased the rate of cell layer formation in the fruit cortex, indicating that BA stimulated cortical cell division. The maximum rate of cell division occurred 10 to 14 days after full bloom (DAFB) when fruit relative growth rate and density reached a maximum and percent dry weight reached a minimum. Cell size in BA-treated fruit was similar to the control. Cell division ended by 35 DAFB in the control and BA-treated fruit when percent dry weight and dry weight began to increase rapidly and fruit density changed from a rapid to a slower rate of decreased density. These data support the hypothesis that BA-induced fruit size increases in `Empire' apple result largely from greater numbers of cells in the fruit cortex, whereas the fruit size increase due to NAA or CB is a consequence of larger cell size.

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Nodrm-1, a Sulphated Lipo-Oligosaccharide Signal of Rhizobium Meliloti Elicits Hair Deformation, Cortical Cell Division and Nodule Organogenesis on Alfalfa Roots

Advances in Molecular Genetics of Plant-Microbe Interactions Vol. 1 - Current Plant Science and Biotechnology in Agriculture ◽

10.1007/978-94-015-7934-6_19 ◽

1991 ◽

pp. 119-126 ◽

Cited By ~ 11

Author(s):

P. Roche ◽

P. Lerouge ◽

J. C. Prome ◽

C. Faucher ◽

J. Vasse ◽

...

Keyword(s):

Cell Division ◽

Rhizobium Meliloti ◽

Cortical Cell

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Effects of nutrition on wool follicle cell kinetics in sheep differing in efficiency of wool production

Australian Journal of Agricultural Research ◽

10.1071/ar9890409 ◽

1989 ◽

Vol 40 (2) ◽

pp. 409 ◽

Cited By ~ 17

Author(s):

PI Hynd

Keyword(s):

Cell Division ◽

Cell Volume ◽

Fibre Diameter ◽

Cortical Cell ◽

High Protein Diet ◽

High Protein ◽

Protein Diet ◽

Low Protein Diet ◽

Low Protein ◽

Fibre Output

Wide phenotypic variation in fibre output per follicle was generated by selecting sheep (five South Australian strongwool Merinos, one finewool Merino and one Corriedale) on this basis, and by offering these sheep a low-protein diet for 9 weeks, followed by a high-protein diet for a further 8 weeks. Clean wool production was measured over the final 3 weeks of each period, while fibre diameter, the rate of length growth of fibres and a number of follicle characters were measured over the last 7 days of each period. The rate of division of follicle bulb cells and the total volume of the germinative region of the follicle was estimated by image-analysis of bulb sections in skin biopsy samples.With the change from the low-protein diet to the high-protein diet, the rate of clean fleece production was increased by 33% (P<0.002), reflecting an increase in fibre diameter (8%) and rate of length growth of fibres (26%); the volume of the germinative region of the average bulb increased 30% (P<0.012) and the rate of bulb cell division by 35% (P<0.004); cortical cell volume also did not change (923 8m3 v. 965 8m3; the average proportion of fibre cross-sectional area occupied by paracortical cells increased from 0.2 1 to 0.35 ( P < 0.01 0); the proportion of dividing cells entering the fibre cortex ranged from 0.25 to 0.42 (mean, 0.31) between sheep on the low-protein diet, and from 0.22 to 0.39 (mean, 0.32) when the animals were fed the high-protein ration; the effect of diet on cell distribution to fibre and inner root sheath was not significant (P<0.601).Phenotypic differences in fibre output were primarily related to differences in the rate of bulb cell division (r= 0.896, P < 0.001), but inclusion of a term for the proportion of bulb cells entering the fibre cortex, removed an additional, significant proportion of the variance. Cortical cell volume, on the other hand, was poorly related to fibre output.

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