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RcRR1, a Rosa canina type-A response regulator gene, is involved in cytokinin-modulated rhizoid organogenesis.

Gao B, Fan L, Li X, Yang H, Liu F, Wang L, Xi L, Ma N, Zhao L - PLoS ONE (2013)

Bottom Line: RcRR1 was found to be localized to the nucleus in GFP-RcRR1 transgenic plants and overexpression of RcRR1 resulted in increased primary root length and lateral root density.More importantly, RcRR1 overexpression transgenic plants also showed reduced sensitivity to cytokinin during root growth; auxin distribution and the expression of auxin efflux carriers PIN genes were altered in RcRR1 overexpression plants.Taken together, these results demonstrate that RcRR1 is a functional type-A response regulator which is involved in cytokinin-regulated rhizoid formation in Rosa canina.

View Article: PubMed Central - PubMed

Affiliation: Department of Ornamental Horticulture and Landscape Architecture, China Agricultural University, Beijing, China.

ABSTRACT
In vitro, a new protocol of plant regeneration in rose was achieved via protocorm-like bodies (PLBs) induced from the root-like organs named rhizoids that developed from leaf explants. The development of rhizoids is a critical stage for efficient regeneration, which is triggered by exogenous auxin. However, the role of cytokinin in the control of organogenesis in rose is as yet uncharacterized. The aim of this study was to elucidate the molecular mechanism of cytokinin-modulated rhizoid formation in Rosa canina. Here, we found that cytokinin is a key regulator in the formation of rhizoids. Treatment with cytokinin reduced callus activity and significantly inhibited rhizoid formation in Rosa canina. We further isolated the full-length cDNA of a type-A response regulator gene of cytokinin signaling, RcRR1, from which the deduced amino acid sequence contained the conserved DDK motif. Gene expression analysis revealed that RcRR1 was differentially expressed during rhizoid formation and its expression level was rapidly up-regulated by cytokinin. In addition, the functionality of RcRR1 was tested in Arabidopsis. RcRR1 was found to be localized to the nucleus in GFP-RcRR1 transgenic plants and overexpression of RcRR1 resulted in increased primary root length and lateral root density. More importantly, RcRR1 overexpression transgenic plants also showed reduced sensitivity to cytokinin during root growth; auxin distribution and the expression of auxin efflux carriers PIN genes were altered in RcRR1 overexpression plants. Taken together, these results demonstrate that RcRR1 is a functional type-A response regulator which is involved in cytokinin-regulated rhizoid formation in Rosa canina.

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Auxin signaling is altered in the RcRR1-OX Arabidopsis.(A, B) DR5::GUS expression in primary root tips of 6-day-old seedlings of wild-type (A) and transgenic (B) plants. Scale bar, 50 µm. (C, D) DR5::GUS expression in lateral roots of 6-day-old seedlings of wild-type (C) and transgenic (D) plants. Scale bar, 50 µm. (E) Expression of auxin efflux carrier genes in the wild-type and transgenic plants. Ubiquitin (UBQ) was used as an internal control.
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pone-0072914-g007: Auxin signaling is altered in the RcRR1-OX Arabidopsis.(A, B) DR5::GUS expression in primary root tips of 6-day-old seedlings of wild-type (A) and transgenic (B) plants. Scale bar, 50 µm. (C, D) DR5::GUS expression in lateral roots of 6-day-old seedlings of wild-type (C) and transgenic (D) plants. Scale bar, 50 µm. (E) Expression of auxin efflux carrier genes in the wild-type and transgenic plants. Ubiquitin (UBQ) was used as an internal control.

Mentions: DR5::GUS is a useful reporter gene, which is widely used for visualizing the distribution of auxin [32], [33]. To investigate whether RcRR1-OX affects the distribution of auxin in Arabidopsis root, the DR5::GUS reporter was transformed into wild-type plants and hybridized with T2 seedlings of RcRR1-OX Arabidopsis. In the wild type, DR5::GUS staining was observed in the root cap and quiescent center (Figure 7A). In contrast, DR5::GUS showed a wider distribution in RcRR1-OX plants which extended to the pericycle and endodermis (Figure 7B). The broadening distribution of auxin was also observed in the lateral roots of RcRR1-OX plants (Figure 7C and 7D). We further studied the effect of RcRR1-OX on the expression of the PIN1, PIN3 and PIN7 genes. As shown in Figure 7E, the expression of these three genes was significantly down-regulated in the RcRR1-OX Arabidopsis in comparison with the wild type (Figure 7E). Our results suggest that RcRR1 might be correlated with the auxin signaling to control root organogenesis.


RcRR1, a Rosa canina type-A response regulator gene, is involved in cytokinin-modulated rhizoid organogenesis.

Gao B, Fan L, Li X, Yang H, Liu F, Wang L, Xi L, Ma N, Zhao L - PLoS ONE (2013)

Auxin signaling is altered in the RcRR1-OX Arabidopsis.(A, B) DR5::GUS expression in primary root tips of 6-day-old seedlings of wild-type (A) and transgenic (B) plants. Scale bar, 50 µm. (C, D) DR5::GUS expression in lateral roots of 6-day-old seedlings of wild-type (C) and transgenic (D) plants. Scale bar, 50 µm. (E) Expression of auxin efflux carrier genes in the wild-type and transgenic plants. Ubiquitin (UBQ) was used as an internal control.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3757009&req=5

pone-0072914-g007: Auxin signaling is altered in the RcRR1-OX Arabidopsis.(A, B) DR5::GUS expression in primary root tips of 6-day-old seedlings of wild-type (A) and transgenic (B) plants. Scale bar, 50 µm. (C, D) DR5::GUS expression in lateral roots of 6-day-old seedlings of wild-type (C) and transgenic (D) plants. Scale bar, 50 µm. (E) Expression of auxin efflux carrier genes in the wild-type and transgenic plants. Ubiquitin (UBQ) was used as an internal control.
Mentions: DR5::GUS is a useful reporter gene, which is widely used for visualizing the distribution of auxin [32], [33]. To investigate whether RcRR1-OX affects the distribution of auxin in Arabidopsis root, the DR5::GUS reporter was transformed into wild-type plants and hybridized with T2 seedlings of RcRR1-OX Arabidopsis. In the wild type, DR5::GUS staining was observed in the root cap and quiescent center (Figure 7A). In contrast, DR5::GUS showed a wider distribution in RcRR1-OX plants which extended to the pericycle and endodermis (Figure 7B). The broadening distribution of auxin was also observed in the lateral roots of RcRR1-OX plants (Figure 7C and 7D). We further studied the effect of RcRR1-OX on the expression of the PIN1, PIN3 and PIN7 genes. As shown in Figure 7E, the expression of these three genes was significantly down-regulated in the RcRR1-OX Arabidopsis in comparison with the wild type (Figure 7E). Our results suggest that RcRR1 might be correlated with the auxin signaling to control root organogenesis.

Bottom Line: RcRR1 was found to be localized to the nucleus in GFP-RcRR1 transgenic plants and overexpression of RcRR1 resulted in increased primary root length and lateral root density.More importantly, RcRR1 overexpression transgenic plants also showed reduced sensitivity to cytokinin during root growth; auxin distribution and the expression of auxin efflux carriers PIN genes were altered in RcRR1 overexpression plants.Taken together, these results demonstrate that RcRR1 is a functional type-A response regulator which is involved in cytokinin-regulated rhizoid formation in Rosa canina.

View Article: PubMed Central - PubMed

Affiliation: Department of Ornamental Horticulture and Landscape Architecture, China Agricultural University, Beijing, China.

ABSTRACT
In vitro, a new protocol of plant regeneration in rose was achieved via protocorm-like bodies (PLBs) induced from the root-like organs named rhizoids that developed from leaf explants. The development of rhizoids is a critical stage for efficient regeneration, which is triggered by exogenous auxin. However, the role of cytokinin in the control of organogenesis in rose is as yet uncharacterized. The aim of this study was to elucidate the molecular mechanism of cytokinin-modulated rhizoid formation in Rosa canina. Here, we found that cytokinin is a key regulator in the formation of rhizoids. Treatment with cytokinin reduced callus activity and significantly inhibited rhizoid formation in Rosa canina. We further isolated the full-length cDNA of a type-A response regulator gene of cytokinin signaling, RcRR1, from which the deduced amino acid sequence contained the conserved DDK motif. Gene expression analysis revealed that RcRR1 was differentially expressed during rhizoid formation and its expression level was rapidly up-regulated by cytokinin. In addition, the functionality of RcRR1 was tested in Arabidopsis. RcRR1 was found to be localized to the nucleus in GFP-RcRR1 transgenic plants and overexpression of RcRR1 resulted in increased primary root length and lateral root density. More importantly, RcRR1 overexpression transgenic plants also showed reduced sensitivity to cytokinin during root growth; auxin distribution and the expression of auxin efflux carriers PIN genes were altered in RcRR1 overexpression plants. Taken together, these results demonstrate that RcRR1 is a functional type-A response regulator which is involved in cytokinin-regulated rhizoid formation in Rosa canina.

Show MeSH
Related in: MedlinePlus