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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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Overexpression of RcRR1 affects the density of lateral root in transgenic Arabidopsis.(A) Statistical analysis of the number of lateral roots (LR) per centimeter of the primary root from the wild-type and transgenic plants. (B) Statistical analysis of the number of LR in the wild-type and transgenic plants treated with 0.2 µg/ml kinetin. Asterisks in (A) and (B) indicate statistically significant differences (Student’s t-test; P<0.01) between the control and transgenic plants; error bars show SDs.
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pone-0072914-g006: Overexpression of RcRR1 affects the density of lateral root in transgenic Arabidopsis.(A) Statistical analysis of the number of lateral roots (LR) per centimeter of the primary root from the wild-type and transgenic plants. (B) Statistical analysis of the number of LR in the wild-type and transgenic plants treated with 0.2 µg/ml kinetin. Asterisks in (A) and (B) indicate statistically significant differences (Student’s t-test; P<0.01) between the control and transgenic plants; error bars show SDs.

Mentions: We functionally characterized the role of RcRR1 in root formation by overexpression of RcRR1 in Arabidopsis. The cDNA fragment containing coding sequences of RcRR1 was fused in-frame to a GFP sequence, and the GFP-RcRR1 fusion gene was placed under the control of a cauliflower mosaic virus (CaMV) 35S promoter. All of these transgenic lines showed high expression levels of GFP-RcRR1 as revealed by RT-PCR (Figure 5A). The RcRR1-OX transgenic plants had a longer primary root than that of the wild type (Figure 5B). Further statistical analysis revealed that the transgenic line #24 had the longest primary root (16% longer than that of wild-type plants) (Figure 5C). As shown in Figure 6A, RcRR1 overexpression also resulted in significantly increased lateral root numbers as compared with wild-type plants. The #24 transgenic plants showed the strongest phenotype with 39% more lateral roots than wild-type plants (Figure 6A).


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)

Overexpression of RcRR1 affects the density of lateral root in transgenic Arabidopsis.(A) Statistical analysis of the number of lateral roots (LR) per centimeter of the primary root from the wild-type and transgenic plants. (B) Statistical analysis of the number of LR in the wild-type and transgenic plants treated with 0.2 µg/ml kinetin. Asterisks in (A) and (B) indicate statistically significant differences (Student’s t-test; P<0.01) between the control and transgenic plants; error bars show SDs.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0072914-g006: Overexpression of RcRR1 affects the density of lateral root in transgenic Arabidopsis.(A) Statistical analysis of the number of lateral roots (LR) per centimeter of the primary root from the wild-type and transgenic plants. (B) Statistical analysis of the number of LR in the wild-type and transgenic plants treated with 0.2 µg/ml kinetin. Asterisks in (A) and (B) indicate statistically significant differences (Student’s t-test; P<0.01) between the control and transgenic plants; error bars show SDs.
Mentions: We functionally characterized the role of RcRR1 in root formation by overexpression of RcRR1 in Arabidopsis. The cDNA fragment containing coding sequences of RcRR1 was fused in-frame to a GFP sequence, and the GFP-RcRR1 fusion gene was placed under the control of a cauliflower mosaic virus (CaMV) 35S promoter. All of these transgenic lines showed high expression levels of GFP-RcRR1 as revealed by RT-PCR (Figure 5A). The RcRR1-OX transgenic plants had a longer primary root than that of the wild type (Figure 5B). Further statistical analysis revealed that the transgenic line #24 had the longest primary root (16% longer than that of wild-type plants) (Figure 5C). As shown in Figure 6A, RcRR1 overexpression also resulted in significantly increased lateral root numbers as compared with wild-type plants. The #24 transgenic plants showed the strongest phenotype with 39% more lateral roots than wild-type plants (Figure 6A).

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