On the Development of the Crown Root Primordia in Rice Plants

Kawata, Shin-ichiro; Harada, Jiro

doi:10.1626/jcs.44.438

Cited by 12 publications

(8 citation statements)

References 6 publications

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“…We performed in situ hybridization experiments to investigate the establishment of the QC during crown root development. Rice crown root development is divided into 12 successive stages (Kawata and Harada, 1975). The primordia are initiated by the periclinal division of several cells of the pericycle layer.…”

Section: Resultsmentioning

confidence: 99%

“…An overlap in the expression of QHB and OsSCR in the outer cell layer of the crown root primordia (Figure 4b,c) also suggests that these cells may contain characteristics of the QC and endodermis. In fact, a precise morphological analysis of rice crown root development revealed that the outer cell layer of crown root primordium forms the epidermis, endodermis, cortex, and root cap (Kawata et al ., 1975).…”

Section: Discussionmentioning

confidence: 99%

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Isolation and characterization of a rice WUSCHEL‐type homeobox gene that is specifically expressed in the central cells of a quiescent center in the root apical meristem

et al. 2003

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SummaryThe Arabidopsis WUSCHEL (WUS) protein, which plays an important role in the speci®cation of the stem cells in the shoot apical meristem (SAM), contains an`atypical' homeodomain (HD) with extra residues in its loop and turn regions. We speculated that a WUS-type atypical HD protein might also be involved in the speci®cation and maintenance of the root apical meristem (RAM) stem cells of rice. To investigate this possibility, we isolated and characterized a rice WUS-type homeobox gene designated quiescent-centerspeci®c homeobox (QHB ) gene. Using transformants carrying the QHB promoter-GUS and in situ hybridization, we found that QHB was speci®cally expressed in the central cells of a quiescent center (QC) of the root. During embryogenesis and crown root formation, QHB expression was observed prior to the morphological differentiation of the root. However, we detected different QHB expression patterns in the process of the RAM development, speci®cally between radicle and crown root formation, suggesting that the cell-fate determination of the QC may be controlled by different mechanisms. We also produced transformants that overexpress QHB or Arabidopsis WUS. These transformants did not form crown roots, but developed multiple shoots from ectopic SAMs with malformed leaves. On the basis of these observations, we propose that the WUS-type homeobox gene is involved in the speci®cation and maintenance of the stem cells (QC cells) in the RAM, by a mechanism similar to that for WUS in the SAM.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Isolation and characterization of a rice WUSCHEL‐type homeobox gene that is specifically expressed in the central cells of a quiescent center in the root apical meristem

et al. 2003

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“…The fundamental difference between cereals and the dicot model plant Arabidopsis thaliana is the presence of an extensive postembryonic shoot-borne root system in cereals, which is missing in Arabidopsis. For example, a field-grown rice plant usually produces hundreds of crown roots, which form a so-called fibrous root system (Kawata and Harada, 1975).…”

Section: Introductionmentioning

confidence: 99%

The WUSCHEL-Related Homeobox GeneWOX11Is Required to Activate Shoot-Borne Crown Root Development in Rice

et al. 2009

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In rice (Oryza sativa), the shoot-borne crown roots are the major root type and are initiated at lower stem nodes as part of normal plant development. However, the regulatory mechanism of crown root development is poorly understood. In this work, we show that a WUSCHEL-related Homeobox (WOX) gene, WOX11, is involved in the activation of crown root emergence and growth. WOX11 was found to be expressed in emerging crown roots and later in cell division regions of the root meristem. The expression could be induced by exogenous auxin or cytokinin. Loss-of-function mutation or downregulation of the gene reduced the number and the growth rate of crown roots, whereas overexpression of the gene induced precocious crown root growth and dramatically increased the root biomass by producing crown roots at the upper stem nodes and the base of florets. The expressions of auxin-and cytokinin-responsive genes were affected in WOX11 overexpression and RNA interference transgenic plants. Further analysis showed that WOX11 directly repressed RR2, a type-A cytokinin-responsive regulator gene that was found to be expressed in crown root primordia. The results suggest that WOX11 may be an integrator of auxin and cytokinin signaling that feeds into RR2 to regulate cell proliferation during crown root development.

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“…In rice, the primordia of CR are initiated from several cells of the pericycle layer adjacent to the peripheral vascular cylinder in the stem (Kaufman 1959). The development of CR was divided into 12 successive stages several years ago (Kawata and Harada 1975). However, based on the results of genetics and molecular biology, the process of rice CR development is now divided into seven stages (Itoh et al 2005): primordia initiation and primordia emergence are divided into different stages, which are controlled by different genes and signaling molecules (Xu et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Cadmium decreases crown root number by decreasing endogenous nitric oxide, which is indispensable for crown root primordia initiation in rice seedlings

Xiong

Han

et al. 2009

Planta

125

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Cadmium (Cd) is toxic to crown roots (CR), which are essential for maintaining normal growth and development in rice seedlings. Nitric oxide (NO) is an important signaling molecule that plays a pivotal role in plant root organogenesis. Here, the effects of Cd on endogenous NO content and root growth conditions were studied in rice seedlings. Results showed that similar to the NO scavenger, cPTIO, Cd significantly decreased endogenous NO content and CR number in rice seedlings, and these decreases were recoverable with the application of sodium nitroprusside (SNP, a NO donor). Microscopic analysis of root collars revealed that treatment with Cd and cPTIO inhibited CR primordia initiation. In contrast, although SNP partially recovered Cd-caused inhibition of CR elongation, treatment with cPTIO had no effect on CR elongation. L: -NMMA, a widely used nitric oxide synthase (NOS) inhibitor, decreased endogenous NO content and CR number significantly, while tungstate, a nitrate reductase (NR) inhibitor, had no effect on endogenous NO content and CR number. Moreover, enzyme activity assays indicated that treatment with SNP inhibited NOS activity significantly, but had no effect on NR activity. All these results support the conclusions that a critical endogenous NO concentration is indispensable for rice CR primordia initiation rather than elongation, NOS is the main source for endogenous NO generation, and Cd decreases CR number by inhibiting NOS activity and thus decreasing endogenous NO content in rice seedlings.

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On the Development of the Crown Root Primordia in Rice Plants

Cited by 12 publications

References 6 publications

Isolation and characterization of a rice WUSCHEL‐type homeobox gene that is specifically expressed in the central cells of a quiescent center in the root apical meristem

Isolation and characterization of a rice WUSCHEL‐type homeobox gene that is specifically expressed in the central cells of a quiescent center in the root apical meristem

The WUSCHEL-Related Homeobox GeneWOX11Is Required to Activate Shoot-Borne Crown Root Development in Rice

Cadmium decreases crown root number by decreasing endogenous nitric oxide, which is indispensable for crown root primordia initiation in rice seedlings

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