Cytokinins are mobile multifunctional plant hormones with roles in development and stress resilience. Although their Histidine Kinase receptors are substantially localised to the endoplasmic reticulum, cellular sites of cytokinin perception and importance of spatially heterogeneous cytokinin distribution continue to be debated. Here we show that cytokinin perception by plasma membrane receptors is an effective additional path for cytokinin response. Readout from a Two Component Signalling cytokinin-specific reporter (TCSn::GFP) closely matches intracellular cytokinin content in roots, yet we also find cytokinins in extracellular fluid, potentially enabling action at the cell surface. Cytokinins covalently linked to beads that could not pass the plasma membrane increased expression of both TCSn::GFP and Cytokinin Response Factors. Super-resolution microscopy of GFP-labelled receptors and diminished TCSn::GFP response to immobilised cytokinins in cytokinin receptor mutants, further indicate that receptors can function at the cell surface. We argue that dual intracellular and surface locations may augment flexibility of cytokinin responses.
- MeSH
- adenin analogy a deriváty farmakologie MeSH
- Arabidopsis cytologie účinky léků genetika metabolismus MeSH
- cytokininy metabolismus MeSH
- extracelulární tekutina metabolismus MeSH
- geneticky modifikované rostliny MeSH
- histidinkinasa genetika metabolismus MeSH
- mutace MeSH
- proteiny huseníčku genetika metabolismus MeSH
- rekombinantní proteiny genetika metabolismus MeSH
- signální transdukce MeSH
- zelené fluorescenční proteiny genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
distribution of auxin within plant tissues is of great importance for developmental plasticity, including root gravitropic growth. Auxin flow is directed by the subcellular polar distribution and dynamic relocalisation of auxin transporters such as the PIN-FORMED (PIN) efflux carriers, which can be influenced by the main natural plant auxin indole-3-acetic acid (IAA). Anthranilic acid (AA) is an important early precursor of IAA and previously published studies with AA analogues have suggested that AA may also regulate PIN localisation. Using Arabidopsis thaliana as a model species, we studied an AA-deficient mutant displaying agravitropic root growth, treated seedlings with AA and AA analogues and transformed lines to over-produce AA while inhibiting its conversion to downstream IAA precursors. We showed that AA rescues root gravitropic growth in the AA-deficient mutant at concentrations that do not rescue IAA levels. Overproduction of AA affects root gravitropism without affecting IAA levels. Treatments with, or deficiency in, AA result in defects in PIN polarity and gravistimulus-induced PIN relocalisation in root cells. Our results revealed a previously unknown role for AA in the regulation of PIN subcellular localisation and dynamics involved in root gravitropism, which is independent of its better known role in IAA biosynthesis.
- MeSH
- Arabidopsis účinky léků metabolismus MeSH
- chinolony farmakologie MeSH
- gravitropismus fyziologie MeSH
- kořeny rostlin anatomie a histologie účinky léků růst a vývoj fyziologie MeSH
- kyseliny indoloctové chemie metabolismus MeSH
- mutace genetika MeSH
- ortoaminobenzoáty chemie metabolismus farmakologie MeSH
- polarita buněk * účinky léků MeSH
- proteiny huseníčku metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Cytokinins are plant hormones that typically block or delay leaf senescence. We profiled 34 different cytokinins/cytokinin metabolites (including precursors, conjugates and degradation products) in leaves of a free-growing mature aspen (Populus tremula) before and after the initiation of autumnal senescence over three consecutive years. The levels and profiles of individual cytokinin species, or classes/groups, varied greatly between years, despite the fact that the onset of autumn senescence was at the same time each year, and senescence was not associated with depletion of either active or total cytokinin levels. Levels of aromatic cytokinins (topolins) were low and changed little over the autumn period. Diurnal variations and weather-dependent variations in cytokinin content were relatively limited. We also followed the expression patterns of all aspen genes implicated as having roles in cytokinin metabolism or signalling, but neither the pattern of regulation of any group of genes nor the expression of any particular gene supported the notion that decreased cytokinin signalling could explain the onset of senescence. Based on the results from this tree, we therefore suggest that cytokinin depletion is unlikely to explain the onset of autumn leaf senescence in aspen.
- MeSH
- biosyntetické dráhy genetika MeSH
- chlorofyl metabolismus MeSH
- cytokininy metabolismus MeSH
- down regulace genetika MeSH
- glukosidy metabolismus MeSH
- listy rostlin metabolismus fyziologie MeSH
- počasí MeSH
- Populus genetika metabolismus fyziologie MeSH
- regulace genové exprese u rostlin MeSH
- roční období MeSH
- rostlinné geny MeSH
- stanovení celkové genové exprese MeSH
- Publikační typ
- časopisecké články MeSH
The plant hormones cytokinins are a convenient target of genetic manipulations that bring benefits in biotechnological applications. The present work demonstrates the importance of the subcellular compartmentalization of cytokinins on the model dicot plant Arabidopsis thaliana and monocot crop Hordeum vulgare. The method of protoplast and vacuole isolation combined with precise cytokinin analysis and recovery assay of a vacuolar marker protein were used to quantify the contents of individual cytokinin forms in the leaf extracellular space, cell interior and vacuole. The data obtained for wild type plants and in each case a specific mutant line allow comparing the effect of genetic manipulations on the hormone distribution and homeostatic balance of cytokinins in the modified plants.
- MeSH
- Arabidopsis genetika metabolismus MeSH
- biotechnologie MeSH
- cytokininy metabolismus MeSH
- extracelulární prostor metabolismus MeSH
- geneticky modifikované rostliny MeSH
- intracelulární prostor metabolismus MeSH
- ječmen (rod) růst a vývoj metabolismus MeSH
- kompartmentace buňky MeSH
- listy rostlin metabolismus MeSH
- membránové transportní proteiny genetika metabolismus MeSH
- mutace MeSH
- proteiny huseníčku genetika metabolismus MeSH
- protoplasty metabolismus MeSH
- regulátory růstu rostlin metabolismus MeSH
- vakuoly metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
