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Brassinazole resistant 1 (BZR1)-dependent brassinosteroid signalling pathway leads to ectopic activation of quiescent cell division and suppresses columella stem cell differentiation.

Lee HS, Kim Y, Pham G, Kim JW, Song JH, Lee Y, Hwang YS, Roux SJ, Kim SH - J. Exp. Bot. (2015)

Bottom Line: BR promotes intense nuclear accumulation of BZR1 in the root tip area, and the binding of BZR1 to the promoters of several root development-regulating genes, modulating their expression in the root stem cell niche area.They could also inhibit auxin-dependent distal stem cell differentiation by antagonizing the auxin/WOX5-dependent pathway.In conclusion, BZR1-/BES1-mediated BR signalling pathways show differential effects on the maintenance of root apical meristem activities: they stimulate ectopic QC division while they show opposite effects on the differentiation of distal columella stem cells in a BR concentration- and BZR1-/BES1-dependent manner.

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Science and Technology, Yonsei University, Wonju, 220-710, Republic of Korea.

No MeSH data available.


Related in: MedlinePlus

Mitotic reactivation of the QC promoted by BZR1-/BES1-mediated BR signalling pathways and their independency of ethylene-induced QC reactivation. (A) BL-induced nuclear localization of BZR1 in the QC, CSC, and CC cells. Images show YFP expression of representative seedlings in longitudinal (upper panel) and radial (lower panel) cross sections. LRC, lateral root cap; EPI, epidermis; COR, cortex; END, endodermis. n>20 seedlings for each treatment. Scale bar, 20 μm. (B) Effects of BL and BR-related genetic background on the frequency of QC cell division. (C) Pictures of representative seedlings used for the cell layer measurements presented in (B). The asterisks (*) represent the position of the QC, determined by morphologic observation. Images show root tips of representative seedlings. (D) Effects of BL and bzr1-D genetic background on the expression of root cell-type markers. The arrows indicate the QC where expression of SCR marker gene is not detected. n>40 seedlings for each treatment. Images show representative reporter expression. All seedlings in (A–D) were grown on 1/2 MS agar media for 7 DAG in the presence (10−10 M) or absence of BL. (E) Effects of ethylene biosynthesis or signalling inhibitors on bzr1-D-mediated QC cell division. Plants were grown on 1/2 MS media for 8 DAG in the presence of absence of the indicated chemicals. AgNO3 (10 μM), CoCl2 (200 μM), AVG (1 μM). n>50 seedlings for each treatment. (F) Effects of BL or a BL-biosynthetic inhibitor on ethylene overproducer, eto1-11. Plants were grown on 1/2 MS media for 6 DAG in the presence of absence of the indicated chemicals. BL (10−10 M), BRZ (10−6 M). n>50 seedlings for each treatment. (G–I) Quantitative RT-PCR analysis of the QC-regulating genes in BL-treated Col-0 and BR-related mutant plants. Col-0 plants were grown on 1/2 MS agar media for 7 DAG and their seedlings were treated with liquid BL for 3h to evaluate short-term effects of BL treatment (G). For evaluation of BL’s long-term effects, Col-0 plants were grown on 1/2 MS agar media for 7 DAG in the presence or absence of BL (H). To analyse expression of QC-related genes in diverse BR mutant plants, Col-0 or En-2 and their mutant plants were grown on 1/2 MS agar media for 8 DAG (I). Values in the graph represent mean expression of genes ± standard deviation, relative to untreated Col-0 control (G and H) or Col-0 or En-2 control (I), which was set as 1.0. The asterisk indicates statistical difference from the mock control (G and H) or from Col-0 or En-2 control (I) at P<0.05(*) or at P<0.01(**). All qRT-PCR analysis was repeated with a minimum of triple biological replicates and the data were statistically analysed by the Student’s t-test. CPD was used as a control for BR-repressed genes. (This figure is available in colour at JXB online.)
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Figure 1: Mitotic reactivation of the QC promoted by BZR1-/BES1-mediated BR signalling pathways and their independency of ethylene-induced QC reactivation. (A) BL-induced nuclear localization of BZR1 in the QC, CSC, and CC cells. Images show YFP expression of representative seedlings in longitudinal (upper panel) and radial (lower panel) cross sections. LRC, lateral root cap; EPI, epidermis; COR, cortex; END, endodermis. n>20 seedlings for each treatment. Scale bar, 20 μm. (B) Effects of BL and BR-related genetic background on the frequency of QC cell division. (C) Pictures of representative seedlings used for the cell layer measurements presented in (B). The asterisks (*) represent the position of the QC, determined by morphologic observation. Images show root tips of representative seedlings. (D) Effects of BL and bzr1-D genetic background on the expression of root cell-type markers. The arrows indicate the QC where expression of SCR marker gene is not detected. n>40 seedlings for each treatment. Images show representative reporter expression. All seedlings in (A–D) were grown on 1/2 MS agar media for 7 DAG in the presence (10−10 M) or absence of BL. (E) Effects of ethylene biosynthesis or signalling inhibitors on bzr1-D-mediated QC cell division. Plants were grown on 1/2 MS media for 8 DAG in the presence of absence of the indicated chemicals. AgNO3 (10 μM), CoCl2 (200 μM), AVG (1 μM). n>50 seedlings for each treatment. (F) Effects of BL or a BL-biosynthetic inhibitor on ethylene overproducer, eto1-11. Plants were grown on 1/2 MS media for 6 DAG in the presence of absence of the indicated chemicals. BL (10−10 M), BRZ (10−6 M). n>50 seedlings for each treatment. (G–I) Quantitative RT-PCR analysis of the QC-regulating genes in BL-treated Col-0 and BR-related mutant plants. Col-0 plants were grown on 1/2 MS agar media for 7 DAG and their seedlings were treated with liquid BL for 3h to evaluate short-term effects of BL treatment (G). For evaluation of BL’s long-term effects, Col-0 plants were grown on 1/2 MS agar media for 7 DAG in the presence or absence of BL (H). To analyse expression of QC-related genes in diverse BR mutant plants, Col-0 or En-2 and their mutant plants were grown on 1/2 MS agar media for 8 DAG (I). Values in the graph represent mean expression of genes ± standard deviation, relative to untreated Col-0 control (G and H) or Col-0 or En-2 control (I), which was set as 1.0. The asterisk indicates statistical difference from the mock control (G and H) or from Col-0 or En-2 control (I) at P<0.05(*) or at P<0.01(**). All qRT-PCR analysis was repeated with a minimum of triple biological replicates and the data were statistically analysed by the Student’s t-test. CPD was used as a control for BR-repressed genes. (This figure is available in colour at JXB online.)

Mentions: For propidium iodide (PI) staining (reported in Figs 1 and 5), roots were incubated for 30min in PI (5 μg/ml), rinsed, and mounted in H2O before confocal microscopic observation.


Brassinazole resistant 1 (BZR1)-dependent brassinosteroid signalling pathway leads to ectopic activation of quiescent cell division and suppresses columella stem cell differentiation.

Lee HS, Kim Y, Pham G, Kim JW, Song JH, Lee Y, Hwang YS, Roux SJ, Kim SH - J. Exp. Bot. (2015)

Mitotic reactivation of the QC promoted by BZR1-/BES1-mediated BR signalling pathways and their independency of ethylene-induced QC reactivation. (A) BL-induced nuclear localization of BZR1 in the QC, CSC, and CC cells. Images show YFP expression of representative seedlings in longitudinal (upper panel) and radial (lower panel) cross sections. LRC, lateral root cap; EPI, epidermis; COR, cortex; END, endodermis. n>20 seedlings for each treatment. Scale bar, 20 μm. (B) Effects of BL and BR-related genetic background on the frequency of QC cell division. (C) Pictures of representative seedlings used for the cell layer measurements presented in (B). The asterisks (*) represent the position of the QC, determined by morphologic observation. Images show root tips of representative seedlings. (D) Effects of BL and bzr1-D genetic background on the expression of root cell-type markers. The arrows indicate the QC where expression of SCR marker gene is not detected. n>40 seedlings for each treatment. Images show representative reporter expression. All seedlings in (A–D) were grown on 1/2 MS agar media for 7 DAG in the presence (10−10 M) or absence of BL. (E) Effects of ethylene biosynthesis or signalling inhibitors on bzr1-D-mediated QC cell division. Plants were grown on 1/2 MS media for 8 DAG in the presence of absence of the indicated chemicals. AgNO3 (10 μM), CoCl2 (200 μM), AVG (1 μM). n>50 seedlings for each treatment. (F) Effects of BL or a BL-biosynthetic inhibitor on ethylene overproducer, eto1-11. Plants were grown on 1/2 MS media for 6 DAG in the presence of absence of the indicated chemicals. BL (10−10 M), BRZ (10−6 M). n>50 seedlings for each treatment. (G–I) Quantitative RT-PCR analysis of the QC-regulating genes in BL-treated Col-0 and BR-related mutant plants. Col-0 plants were grown on 1/2 MS agar media for 7 DAG and their seedlings were treated with liquid BL for 3h to evaluate short-term effects of BL treatment (G). For evaluation of BL’s long-term effects, Col-0 plants were grown on 1/2 MS agar media for 7 DAG in the presence or absence of BL (H). To analyse expression of QC-related genes in diverse BR mutant plants, Col-0 or En-2 and their mutant plants were grown on 1/2 MS agar media for 8 DAG (I). Values in the graph represent mean expression of genes ± standard deviation, relative to untreated Col-0 control (G and H) or Col-0 or En-2 control (I), which was set as 1.0. The asterisk indicates statistical difference from the mock control (G and H) or from Col-0 or En-2 control (I) at P<0.05(*) or at P<0.01(**). All qRT-PCR analysis was repeated with a minimum of triple biological replicates and the data were statistically analysed by the Student’s t-test. CPD was used as a control for BR-repressed genes. (This figure is available in colour at JXB online.)
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Related In: Results  -  Collection

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Figure 1: Mitotic reactivation of the QC promoted by BZR1-/BES1-mediated BR signalling pathways and their independency of ethylene-induced QC reactivation. (A) BL-induced nuclear localization of BZR1 in the QC, CSC, and CC cells. Images show YFP expression of representative seedlings in longitudinal (upper panel) and radial (lower panel) cross sections. LRC, lateral root cap; EPI, epidermis; COR, cortex; END, endodermis. n>20 seedlings for each treatment. Scale bar, 20 μm. (B) Effects of BL and BR-related genetic background on the frequency of QC cell division. (C) Pictures of representative seedlings used for the cell layer measurements presented in (B). The asterisks (*) represent the position of the QC, determined by morphologic observation. Images show root tips of representative seedlings. (D) Effects of BL and bzr1-D genetic background on the expression of root cell-type markers. The arrows indicate the QC where expression of SCR marker gene is not detected. n>40 seedlings for each treatment. Images show representative reporter expression. All seedlings in (A–D) were grown on 1/2 MS agar media for 7 DAG in the presence (10−10 M) or absence of BL. (E) Effects of ethylene biosynthesis or signalling inhibitors on bzr1-D-mediated QC cell division. Plants were grown on 1/2 MS media for 8 DAG in the presence of absence of the indicated chemicals. AgNO3 (10 μM), CoCl2 (200 μM), AVG (1 μM). n>50 seedlings for each treatment. (F) Effects of BL or a BL-biosynthetic inhibitor on ethylene overproducer, eto1-11. Plants were grown on 1/2 MS media for 6 DAG in the presence of absence of the indicated chemicals. BL (10−10 M), BRZ (10−6 M). n>50 seedlings for each treatment. (G–I) Quantitative RT-PCR analysis of the QC-regulating genes in BL-treated Col-0 and BR-related mutant plants. Col-0 plants were grown on 1/2 MS agar media for 7 DAG and their seedlings were treated with liquid BL for 3h to evaluate short-term effects of BL treatment (G). For evaluation of BL’s long-term effects, Col-0 plants were grown on 1/2 MS agar media for 7 DAG in the presence or absence of BL (H). To analyse expression of QC-related genes in diverse BR mutant plants, Col-0 or En-2 and their mutant plants were grown on 1/2 MS agar media for 8 DAG (I). Values in the graph represent mean expression of genes ± standard deviation, relative to untreated Col-0 control (G and H) or Col-0 or En-2 control (I), which was set as 1.0. The asterisk indicates statistical difference from the mock control (G and H) or from Col-0 or En-2 control (I) at P<0.05(*) or at P<0.01(**). All qRT-PCR analysis was repeated with a minimum of triple biological replicates and the data were statistically analysed by the Student’s t-test. CPD was used as a control for BR-repressed genes. (This figure is available in colour at JXB online.)
Mentions: For propidium iodide (PI) staining (reported in Figs 1 and 5), roots were incubated for 30min in PI (5 μg/ml), rinsed, and mounted in H2O before confocal microscopic observation.

Bottom Line: BR promotes intense nuclear accumulation of BZR1 in the root tip area, and the binding of BZR1 to the promoters of several root development-regulating genes, modulating their expression in the root stem cell niche area.They could also inhibit auxin-dependent distal stem cell differentiation by antagonizing the auxin/WOX5-dependent pathway.In conclusion, BZR1-/BES1-mediated BR signalling pathways show differential effects on the maintenance of root apical meristem activities: they stimulate ectopic QC division while they show opposite effects on the differentiation of distal columella stem cells in a BR concentration- and BZR1-/BES1-dependent manner.

View Article: PubMed Central - PubMed

Affiliation: Division of Biological Science and Technology, Yonsei University, Wonju, 220-710, Republic of Korea.

No MeSH data available.


Related in: MedlinePlus