Hormone perception and signaling pathways have a fundamental regulatory function in the physiological processes of plants. Cytokinins, a class of plant hormones, regulate cell division and meristem maintenance. The cytokinin signaling pathway is well established in the model plant Arabidopsisthaliana. Several negative feedback mechanisms, tightly controlling cytokinin signaling output, have been described previously. In this study, we identified a new feedback mechanism executed through alternative splicing of the cytokinin receptor AHK4/CRE1. A novel splicing variant named CRE1int7 results from seventh intron retention, introducing a premature termination codon in the transcript. We showed that CRE1int7 is translated in planta into a truncated receptor lacking the C-terminal receiver domain essential for signal transduction. CRE1int7 can bind cytokinin but cannot activate the downstream cascade. We present a novel negative feedback mechanism of the cytokinin signaling pathway, facilitated by a decoy receptor that can inactivate canonical cytokinin receptors via dimerization and compete with them for ligand binding. Ensuring proper plant growth and development requires precise control of the cytokinin signaling pathway at several levels. CRE1int7 represents a so-far unknown mechanism for fine-tuning the cytokinin signaling pathway in Arabidopsis.
- MeSH
- alternativní sestřih * MeSH
- Arabidopsis * metabolismus genetika MeSH
- cytokininy * metabolismus MeSH
- proteiny huseníčku * metabolismus genetika MeSH
- receptory buněčného povrchu metabolismus genetika MeSH
- regulace genové exprese u rostlin MeSH
- signální transdukce * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- cytokininy * MeSH
- proteiny huseníčku * MeSH
- receptory buněčného povrchu MeSH
The development of above-ground lateral organs is initiated at the peripheral zone of the shoot apical meristem (SAM). The coordination of cell fate determination and the maintenance of stem cells are achieved through a complex regulatory network comprised of transcription factors. Two AP2/ERF transcription factor family genes, ESR1/DRN and ESR2/DRNL/SOB/BOL, regulate cotyledon and flower formation and de novo organogenesis in tissue culture. However, their roles in post-embryonic lateral organ development remain elusive. In this study, we analyzed the genetic interactions among SAM-related genes, WUS and STM, two ESR genes, and one of the HD-ZIP III members, REV, whose protein product interacts with ESR1 in planta. We found that esr1 mutations substantially enhanced the wus and stm phenotypes, which bear a striking resemblance to those of the wus rev and stm rev double mutants, respectively. Aberrant adaxial-abaxial polarity is observed in wus esr1 at relatively low penetrance. On the contrary, the esr2 mutation partially suppressed stm phenotypes in the later vegetative phase. Such complex genetic interactions appear to be attributed to the distinct expression pattern of two ESR genes because the ESR1 promoter-driving ESR2 is capable of rescuing phenotypes caused by the esr1 mutation. Our results pose the unique genetic relevance of ESR1 and the SAM-related gene interactions in the development of rosette leaves.
- Klíčová slova
- Arabidopsis thaliana, ENHANCER OF SHOOT REGENERATION 1, REVOLTA, SHOOTMERISTEMLESS, WUSCHEL, adaxial–abaxial polarity, lateral organ, shoot apical meristem,
- MeSH
- Arabidopsis genetika růst a vývoj MeSH
- fenotyp MeSH
- homeodoménové proteiny genetika MeSH
- listy rostlin genetika růst a vývoj MeSH
- meristém genetika růst a vývoj MeSH
- mutace MeSH
- organogeneze rostlin genetika MeSH
- proteiny huseníčku genetika MeSH
- regulace genové exprese u rostlin * MeSH
- rostlinné geny * MeSH
- transkripční faktory genetika MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- ESR1 protein, Arabidopsis MeSH Prohlížeč
- homeodoménové proteiny MeSH
- proteiny huseníčku MeSH
- transkripční faktory MeSH
- WUSCHEL protein, Arabidopsis MeSH Prohlížeč
Among the major phytohormones, the cytokinin exhibits unique features for its ability to positively affect the developmental status of plastids. Even early on in its research, cytokinins were known to promote plastid differentiation and to reduce the loss of chlorophyll in detached leaves. Since the discovery of the components of cytokinin perception and primary signaling, the genes involved in photosynthesis and plastid differentiation have been identified as those directly targeted by type-B response regulators. Furthermore, cytokinins are known to modulate versatile cellular processes such as promoting the division and differentiation of cells and, in concert with auxin, initiating the de novo formation of shoot apical meristem (SAM) in tissue cultures. Yet how cytokinins precisely participate in such diverse cellular phenomena, and how the associated cellular processes are coordinated as a whole, remains unclear. A plausible presumption that would account for the coordinated gene expression is the tight and reciprocal communication between the nucleus and plastid. The fact that cytokinins affect plastid developmental status via gene expression in both the nucleus and plastid is interpreted here to suggest that cytokinin functions as an initiator of anterograde (nucleus-to-plastid) signaling. Based on this viewpoint, we first summarize the physiological relevance of cytokinins to the coordination of plastid differentiation with de novo shoot organogenesis in tissue culture systems. Next, the role of endogenous cytokinins in influencing plastid differentiation within the SAM of intact plants is discussed. Finally, a presumed plastid-derived signal in response to cytokinins for coupled nuclear gene expression is proposed.
- Klíčová slova
- WUSCHEL, anterograde signaling, chloroplast, cytokinin, organelle communication, retrograde signaling, shoot apical meristem, tissue culture,
- Publikační typ
- časopisecké články MeSH
Most of the transcribed genes in eukaryotic cells are interrupted by intervening sequences called introns that are co-transcriptionally removed from nascent messenger RNA through the process of splicing. In Arabidopsis, 79% of genes contain introns and more than 60% of intron-containing genes undergo alternative splicing (AS), which ostensibly is considered to increase protein diversity as one of the intrinsic mechanisms for fitness to the varying environment or the internal developmental program. In addition, recent findings have prevailed in terms of overlooked intron functions. Here, we review recent progress in the underlying mechanisms of intron function, in particular by focusing on unique features of the first intron that is located in close proximity to the transcription start site. The distinct deposition of epigenetic marks and nucleosome density on the first intronic DNA sequence, the impact of the first intron on determining the transcription start site and elongation of its own expression (called intron-mediated enhancement, IME), translation control in 5'-UTR, and the new mechanism of the trans-acting function of the first intron in regulating gene expression at the post-transcriptional level are summarized.
- Klíčová slova
- alternative splicing, first intron, intron-mediated enhancement, upstream ORF,
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Cytokinin plant hormones have been shown to play an important role in plant response to abiotic stresses. Herein, we expand upon the findings of Pospíšilová et al. [30] regarding preparation of novel transgenic barley lines overexpressing cytokinin dehydrogenase 1 gene from Arabidopsis under the control of mild root-specific promotor of maize β-glycosidase. These lines showed drought-tolerant phenotype mainly due to alteration of root architecture and stronger lignification of root tissue. A detailed transcriptomic analysis of roots of transgenic plants subjected to revitalization after drought stress revealed attenuated response through the HvHK3 cytokinin receptor and up-regulation of two transcription factors implicated in stress responses and abscisic acid sensitivity. Increased expression of several genes involved in the phenylpropanoid pathway as well as of genes encoding arogenate dehydratase/lyase participating in phenylalanine synthesis was found in roots during revitalization. Although more precursors of lignin synthesis were present in roots after drought stress, final lignin accumulation did not change compared to that in plants grown under optimal conditions. Changes in transcriptome indicated a higher auxin turnover in transgenic roots. The same analysis in leaves revealed that genes encoding putative enzymes responsible for production of jasmonates and other volatile compounds were up-regulated. Although transgenic barley leaves showed lower chlorophyll content and down-regulation of genes encoding proteins involved in photosynthesis than did wild-type plants when cultivated under optimal conditions, they did show a tendency to return to initial photochemical activities faster than did wild-type leaves when re-watered after severe drought stress. In contrast to optimal conditions, comparative transcriptomic analysis of revitalized leaves displayed up-regulation of genes encoding enzymes and proteins involved in photosynthesis, and especially those encoded by the chloroplast genome. Taken together, our results indicate that the partial cytokinin insensitivity induced in barley overexpressing cytokinin dehydrogenase contributes to tolerance to drought stress.
- MeSH
- aklimatizace genetika fyziologie MeSH
- biotechnologie MeSH
- cytokininy metabolismus MeSH
- fotosyntéza MeSH
- fyziologický stres MeSH
- geneticky modifikované rostliny MeSH
- homeostáza MeSH
- ječmen (rod) genetika fyziologie MeSH
- kořeny rostlin genetika metabolismus MeSH
- období sucha MeSH
- oxidoreduktasy genetika metabolismus MeSH
- proteiny huseníčku genetika metabolismus MeSH
- regulátory růstu rostlin metabolismus MeSH
- rostlinné geny MeSH
- rostlinné proteiny genetika metabolismus MeSH
- stanovení celkové genové exprese MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- cytokinin oxidase MeSH Prohlížeč
- cytokininy MeSH
- oxidoreduktasy MeSH
- proteiny huseníčku MeSH
- regulátory růstu rostlin MeSH
- rostlinné proteiny MeSH
