The plant-specific receptor-like cytoplasmic kinases (RLCKs) form a large, poorly characterized family. Members of the RLCK VI_A class of dicots have a unique characteristic: their activity is regulated by Rho-of-plants (ROP) GTPases. The biological function of one of these kinases was investigated using a T-DNA insertion mutant and RNA interference. Loss of RLCK VI_A2 function resulted in restricted cell expansion and seedling growth. Although these phenotypes could be rescued by exogenous gibberellin, the mutant did not exhibit lower levels of active gibberellins nor decreased gibberellin sensitivity. Transcriptome analysis confirmed that gibberellin is not the direct target of the kinase; its absence rather affected the metabolism and signalling of other hormones such as auxin. It is hypothesized that gibberellins and the RLCK VI_A2 kinase act in parallel to regulate cell expansion and plant growth. Gene expression studies also indicated that the kinase might have an overlapping role with the transcription factor circuit (PIF4-BZR1-ARF6) controlling skotomorphogenesis-related hypocotyl/cotyledon elongation. Furthermore, the transcriptomic changes revealed that the loss of RLCK VI_A2 function alters cellular processes that are associated with cell membranes, take place at the cell periphery or in the apoplast, and are related to cellular transport and/or cell wall reorganisation.
- MeSH
- Arabidopsis účinky léků enzymologie genetika růst a vývoj MeSH
- DNA bakterií genetika metabolismus MeSH
- DNA vazebné proteiny genetika metabolismus MeSH
- geneticky modifikované rostliny MeSH
- gibereliny metabolismus farmakologie MeSH
- hypokotyl účinky léků enzymologie genetika růst a vývoj MeSH
- inzerční mutageneze MeSH
- kotyledon účinky léků enzymologie genetika růst a vývoj MeSH
- kyseliny indoloctové metabolismus farmakologie MeSH
- protein-serin-threoninkinasy genetika metabolismus MeSH
- proteiny huseníčku genetika metabolismus MeSH
- regulace genové exprese u rostlin * MeSH
- regulátory růstu rostlin farmakologie MeSH
- semenáček účinky léků enzymologie genetika růst a vývoj MeSH
- stanovení celkové genové exprese MeSH
- transkripční faktory bHLH genetika metabolismus MeSH
- transkripční faktory genetika metabolismus MeSH
- transkriptom MeSH
- vývojová regulace genové exprese MeSH
- Publikační typ
- časopisecké články MeSH
The collet (root-hypocotyl junction) region is an important plant transition zone between soil and atmospheric environments. Despite its crucial importance for plant development, little is known about how this transition zone is specified. Here we document the involvement of the exocyst complex in this process. The exocyst, an octameric tethering complex, participates in secretion and membrane recycling and is central to numerous cellular and developmental processes, such as growth of root hairs, cell expansion, recycling of PIN auxin efflux carriers and many others. We show that dark-grown Arabidopsis mutants deficient in exocyst subunits can form a hair-bearing ectopic collet-like structure above the true collet, morphologically resembling the true collet but also retaining some characteristics of the hypocotyl. The penetrance of this phenotypic defect is significantly influenced by cultivation temperature and carbon source, and is related to a defect in auxin regulation. These observations provide new insights into the regulation of collet region formation and developmental plasticity of the hypocotyl.
In plants, the multistep phosphorelay (MSP) pathway mediates a range of regulatory processes, including those activated by cytokinins. The cross talk between cytokinin response and light has been known for a long time. However, the molecular mechanism underlying the interaction between light and cytokinin signaling remains elusive. In the screen for upstream regulators we identified a LONG PALE HYPOCOTYL (LPH) gene whose activity is indispensable for spatiotemporally correct expression of CYTOKININ INDEPENDENT1 (CKI1), encoding the constitutively active sensor His kinase that activates MSP signaling. lph is a new allele of HEME OXYGENASE1 (HY1) that encodes the key protein in the biosynthesis of phytochromobilin, a cofactor of photoconvertible phytochromes. Our analysis confirmed the light-dependent regulation of the CKI1 expression pattern. We show that CKI1 expression is under the control of phytochrome A (phyA), functioning as a dual (both positive and negative) regulator of CKI1 expression, presumably via the phyA-regulated transcription factors (TF) PHYTOCHROME INTERACTING FACTOR3 and CIRCADIAN CLOCK ASSOCIATED1. Changes in CKI1 expression observed in lph/hy1-7 and phy mutants correlate with misregulation of MSP signaling, changed cytokinin sensitivity, and developmental aberrations that were previously shown to be associated with cytokinin and/or CKI1 action. Besides that, we demonstrate a novel role of phyA-dependent CKI1 expression in the hypocotyl elongation and hook development during skotomorphogenesis. Based on these results, we propose that the light-dependent regulation of CKI1 provides a plausible mechanistic link underlying the well-known interaction between light- and cytokinin-controlled plant development.
- MeSH
- Arabidopsis genetika metabolismus účinky záření MeSH
- cytokininy metabolismus MeSH
- fytochrom A genetika metabolismus MeSH
- geneticky modifikované rostliny MeSH
- hemová oxygenasa (decyklizující) genetika metabolismus MeSH
- hypokotyl genetika metabolismus účinky záření MeSH
- modely genetické MeSH
- mutace MeSH
- proteinkinasy genetika metabolismus MeSH
- proteiny huseníčku genetika metabolismus MeSH
- regulace genové exprese u rostlin genetika účinky záření MeSH
- signální transdukce genetika účinky záření MeSH
- světlo * MeSH
- Publikační typ
- časopisecké články MeSH
As sessile organisms, plants must sense environmental conditions and adjust their growth and development processes accordingly, through adaptive responses regulated by various internal factors, including hormones. A key environmental factor is temperature, but temperature-sensing mechanisms are not fully understood despite intense research. We investigated proteomic responses to temperature shocks (15 min cold or heat treatments) with and without exogenous applications of cytokinin in Arabidopsis. Image and mass spectrometric analysis of the two-dimensionally separated proteins detected 139 differentially regulated spots, in which 148 proteins were identified, most of which have not been previously linked to temperature perception. More than 70% of the temperature-shock response proteins were modulated by cytokinin, mostly in a similar manner as heat shock. Data mining of previous transcriptomic datasets supported extensive interactions between temperature and cytokinin signalling. The biological significance of this finding was tested by assaying an independent growth response of Arabidopsis seedlings to heat stress: hypocotyl elongation. This response was strongly inhibited in mutants with deficiencies in cytokinin signalling or endogenous cytokinin levels. Thus, cytokinins may directly participate in heat signalling in plants. Finally, large proportions of both temperature-shock and cytokinin responsive proteomes co-localize to the chloroplast, which might therefore host a substantial proportion of the temperature response machinery.
- MeSH
- Arabidopsis genetika růst a vývoj MeSH
- biologické modely MeSH
- cytokininy farmakologie MeSH
- fosforylace účinky léků MeSH
- geneticky modifikované rostliny MeSH
- hypokotyl účinky léků genetika růst a vývoj MeSH
- metabolismus sacharidů účinky léků genetika MeSH
- mutace MeSH
- proteiny huseníčku klasifikace genetika metabolismus MeSH
- proteom metabolismus MeSH
- reakce na tepelný šok genetika MeSH
- rostlinné geny MeSH
- teplota * MeSH
- transkriptom účinky léků genetika MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
