Auxin and cytokinin interaction plays an essential role in a wide range of plant growth and developmental processes. The interaction consequence of the two hormones is highly tissue specific. The molecular mechanisms ...Auxin and cytokinin interaction plays an essential role in a wide range of plant growth and developmental processes. The interaction consequence of the two hormones is highly tissue specific. The molecular mechanisms underlying the tissue specificity are largely unknown. Here we show that the cytokinin signaling pathway key components ARR5 and ARR6 respond to auxin with a highly tissue specific and contrasted pattern in Arabidopsis seedlings and calli in the presence of cytokinin. Our results suggest that the two highly homologous but functionally distinct genes, ARR5 and ARR6, play a critical role in mediating tissue specific interaction between auxin and cytokinin.展开更多
As the first and rate-limiting enzyme of proline degradation, PROLINE DEHYDROGENASE1 （PDH1） is tightly regulated during plant stress responses, including induction under hypoosmolarity and repression under water def...As the first and rate-limiting enzyme of proline degradation, PROLINE DEHYDROGENASE1 （PDH1） is tightly regulated during plant stress responses, including induction under hypoosmolarity and repression under water deficit. The plant receptor histidine kinases AHKs, elements of the two-component system （TCS） in Arabidopsis thaliana, are pro- posed to function in water stress responses by regulating different stress-responsive genes. However, little information is available concerning AHK phosphorelay-mediated downstream signaling. Here we show that the Arabidopsis type-B response regulator 18 （ARR18） functions as a positive osmotic stress response regulator in Arabidopsis seeds and affects the activity of the PDH1 promoter, known to be controlled by C-group bZlP transcription factors. Moreover, direct physical interaction of ARR18 with bZIP63 was identified and shown to be dependent on phosphorylation of the conserved aspar- tate residue in the ARR18 receiver domain. We further show that bZlP63 itself functions as a negative regulator of seed germination upon osmotic stress. Using reporter gene assays in protoplasts, we demonstrated that ARR18 interaction negatively interferes with the transcriptional activity of bZIP63 on the PDH1 promoter. Our findings provide new insight into the function of ARR18 and bZIP63 as antagonistic regulators of gene expression in Arabidopsis.展开更多
Auxin and cytokinin direct cell proliferation and differentiation during the in vitro culture of plant cells, but the molecular basis of these processes, especially de novo shoot regeneration, has not been fully eluci...Auxin and cytokinin direct cell proliferation and differentiation during the in vitro culture of plant cells, but the molecular basis of these processes, especially de novo shoot regeneration, has not been fully elucidated. Here, we describe the regulatory control of shoot regeneration in Arabidopsis thaliana(L.) Heynh, based on the interaction of ARABIDOPSIS RESPONSE REGULATOR12(ARR12) and WUSCHEL(WUS). The major site of ARR12 expression coincided with the location where the shoot apical meristem(SAM) initiated. The oar12 mutants showed severely impaired shoot regeneration and reduced responsiveness to cytokinin; consistent with this, the overexpression of ARR12 enhanced shoot regeneration.Certain shoot meristem specification genes, notably WUSCHEL(WUS) and CLAVATA3, were significantly downregulated in the arr1z explants. Chromatin immunoprecipitation(ChIP) and transient activation assays demonstrated that ARR12 binds to the promoter of WUS. These observations indicate that during shoot regeneration, in vitro, ARR12 functions as a molecular link between cytokinin signaling and the expression of shoot meristem specification genes.展开更多
文摘Auxin and cytokinin interaction plays an essential role in a wide range of plant growth and developmental processes. The interaction consequence of the two hormones is highly tissue specific. The molecular mechanisms underlying the tissue specificity are largely unknown. Here we show that the cytokinin signaling pathway key components ARR5 and ARR6 respond to auxin with a highly tissue specific and contrasted pattern in Arabidopsis seedlings and calli in the presence of cytokinin. Our results suggest that the two highly homologous but functionally distinct genes, ARR5 and ARR6, play a critical role in mediating tissue specific interaction between auxin and cytokinin.
文摘As the first and rate-limiting enzyme of proline degradation, PROLINE DEHYDROGENASE1 （PDH1） is tightly regulated during plant stress responses, including induction under hypoosmolarity and repression under water deficit. The plant receptor histidine kinases AHKs, elements of the two-component system （TCS） in Arabidopsis thaliana, are pro- posed to function in water stress responses by regulating different stress-responsive genes. However, little information is available concerning AHK phosphorelay-mediated downstream signaling. Here we show that the Arabidopsis type-B response regulator 18 （ARR18） functions as a positive osmotic stress response regulator in Arabidopsis seeds and affects the activity of the PDH1 promoter, known to be controlled by C-group bZlP transcription factors. Moreover, direct physical interaction of ARR18 with bZIP63 was identified and shown to be dependent on phosphorylation of the conserved aspar- tate residue in the ARR18 receiver domain. We further show that bZlP63 itself functions as a negative regulator of seed germination upon osmotic stress. Using reporter gene assays in protoplasts, we demonstrated that ARR18 interaction negatively interferes with the transcriptional activity of bZIP63 on the PDH1 promoter. Our findings provide new insight into the function of ARR18 and bZIP63 as antagonistic regulators of gene expression in Arabidopsis.
基金financially supported by the National Special Science Research Program of China (grant no.2013CB967300)the National High Technology Research and Development Program "863”(grant no.2013AA102602-4)+2 种基金the National Key Research and Development Program of China (grant no.2016YFD0101902)National Transgenic Project of China (Grant No.2016ZX08010002-002)the National Natural Science Foundation (grant nos.31471515,31500232,31270328,30970243)
文摘Auxin and cytokinin direct cell proliferation and differentiation during the in vitro culture of plant cells, but the molecular basis of these processes, especially de novo shoot regeneration, has not been fully elucidated. Here, we describe the regulatory control of shoot regeneration in Arabidopsis thaliana(L.) Heynh, based on the interaction of ARABIDOPSIS RESPONSE REGULATOR12(ARR12) and WUSCHEL(WUS). The major site of ARR12 expression coincided with the location where the shoot apical meristem(SAM) initiated. The oar12 mutants showed severely impaired shoot regeneration and reduced responsiveness to cytokinin; consistent with this, the overexpression of ARR12 enhanced shoot regeneration.Certain shoot meristem specification genes, notably WUSCHEL(WUS) and CLAVATA3, were significantly downregulated in the arr1z explants. Chromatin immunoprecipitation(ChIP) and transient activation assays demonstrated that ARR12 binds to the promoter of WUS. These observations indicate that during shoot regeneration, in vitro, ARR12 functions as a molecular link between cytokinin signaling and the expression of shoot meristem specification genes.
