BACKGROUND: De-etiolation is the switch from skoto- to photomorphogenesis, enabling the heterotrophic etiolated seedling to develop into an autotrophic plant. Upon exposure to blue light (BL), reduction of hypocotyl growth rate occurs in two phases: a rapid inhibition mediated by phototropin 1 (PHOT1) within the first 30-40 min of illumination, followed by the cryptochrome 1 (CRY1)-controlled establishment of the steady-state growth rate. Although some information is available for CRY1-mediated de-etiolation, less attention has been given to the PHOT1 phase of de-etiolation. RESULTS: We generated a subtracted cDNA library using the suppression subtractive hybridization method to investigate the molecular mechanisms of BL-induced de-etiolation in tomato (Solanum lycopersicum L.), an economically important crop. We focused our interest on the first 30 min following the exposure to BL when PHOT1 is required to induce the process. Our library generated 152 expressed sequence tags that were found to be rapidly accumulated upon exposure to BL and consequently potentially regulated by PHOT1. Annotation revealed that biological functions such as modification of chromatin structure, cell wall modification, and transcription/translation comprise an important part of events contributing to the establishment of photomorphogenesis in young tomato seedlings. Our conclusions based on bioinformatics data were supported by qRT-PCR analyses the specific investigation of V-H(+)-ATPase during de-etiolation in tomato. CONCLUSIONS: Our study provides the first report dealing with understanding the PHOT1-mediated phase of de-etiolation. Using subtractive cDNA library, we were able to identify important regulatory mechanisms. The profound induction of transcription/translation, as well as modification of chromatin structure, is relevant in regard to the fact that the entry into photomorphogenesis is based on a deep reprograming of the cell. Also, we postulated that BL restrains the cell expansion by the rapid modification of the cell wall.

• Klíčová slova
• Blue light, De-etiolation, Suppression subtractive hybridization, Tomato (Solanum lycopersicum L.),
• MeSH
• chromatin ultrastruktura   MeSH
• etiolizace genetika   MeSH
• fototropiny fyziologie   MeSH
• genová knihovna MeSH
• genové regulační sítě MeSH
• hypokotyl růst a vývoj   MeSH
• regulace genové exprese u rostlin MeSH
• semenáček genetika   růst a vývoj   MeSH
• Solanum lycopersicum genetika   růst a vývoj   MeSH
• světlo * MeSH
• upregulace MeSH
• vakuolární protonové ATPasy genetika   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chromatin MeSH
• fototropiny MeSH
• vakuolární protonové ATPasy MeSH

BACKGROUND AND AIMS: Cytokinins are positive regulators of shoot development. However, it has previously been demonstrated that efficient activation of the cytokinin biosynthesis gene ipt can cause necrotic lesions and wilting in tobacco leaves. Some plant pathogens reportedly use their ability to produce cytokinins in disease development. In response to pathogen attacks, plants can trigger a hypersensitive response that rapidly kills cells near the infection site, depriving the pathogen of nutrients and preventing its spread. In this study, a diverse set of processes that link ipt activation to necrotic lesion formation were investigated in order to evaluate the potential of cytokinins as signals and/or mediators in plant defence against pathogens. METHODS: The binary pOp-ipt/LhGR system for dexamethasone-inducible ipt expression was used to increase endogenous cytokinin levels in transgenic tobacco. Changes in the levels of cytokinins and the stress hormones salicylic, jasmonic and abscisic acid following ipt activation were determined by ultra-performance liquid chromatography-electrospray tandem mass spectrometry (UPLC-MS/MS). Trends in hydrogen peroxide content and lipid peroxidation were monitored using the potassium iodide and malondialdehyde assays. The subcellular distribution of hydrogen peroxide was investigated using 3,3'-diaminobenzidine staining. The dynamics of transcripts related to photosynthesis and pathogen response were analysed by reverse transcription followed by quantitative PCR. The effects of cytokinins on photosynthesis were deciphered by analysing changes in chlorophyll fluorescence and leaf gas exchange. KEY RESULTS: Plants can produce sufficiently high levels of cytokinins to trigger fast cell death without any intervening chlorosis - a hallmark of the hypersensitive response. The results suggest that chloroplastic hydrogen peroxide orchestrates the molecular responses underpinning the hypersensitive-like response, including the inhibition of photosynthesis, elevated levels of stress hormones, oxidative membrane damage and stomatal closure. CONCLUSIONS: Necrotic lesion formation triggered by ipt activation closely resembles the hypersensitive response. Cytokinins may thus act as signals and/or mediators in plant defence against pathogen attack.

• Klíčová slova
• Cytokinin, Nicotiana tabacum, abscisic acid, hydrogen peroxide, hypersensitive response, jasmonic acid, lipid peroxidation, non-photochemical quenching, pathogenesis-related proteins, photosynthesis, salicylic acid, stomatal conductance,
• MeSH
• alkyltransferasy a aryltransferasy genetika   MeSH
• buněčná smrt MeSH
• chlorofyl metabolismus   MeSH
• chloroplasty genetika   metabolismus   MeSH
• cytokininy genetika   metabolismus   MeSH
• dexamethason farmakologie   MeSH
• fotosyntéza genetika   MeSH
• geneticky modifikované rostliny MeSH
• interakce hostitele a patogenu * MeSH
• listy rostlin cytologie   genetika   fyziologie   MeSH
• nekróza genetika   MeSH
• oxidační stres genetika   MeSH
• peroxid vodíku metabolismus   MeSH
• peroxidace lipidů MeSH
• průduchy rostlin fyziologie   MeSH
• regulace genové exprese u rostlin účinky léků   MeSH
• regulátory růstu rostlin genetika   metabolismus   MeSH
• tabák genetika   mikrobiologie   fyziologie   MeSH
• umlčování genů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenylate isopentenyltransferase MeSH Prohlížeč
• alkyltransferasy a aryltransferasy MeSH
• chlorofyl MeSH
• cytokininy MeSH
• dexamethason MeSH
• peroxid vodíku MeSH
• regulátory růstu rostlin MeSH

Light is one of the most important factor influencing plant growth and development all through their life cycle. One of the well-known light-regulated processes is de-etiolation, i.e. the switch from skotomorphogenesis to photomorphogenesis. The hormones cytokinins (CKs) play an important role during the establishment of photomorphogenesis as exogenous CKs induced photomorphogenesis of dark-grown seedlings. Most of the studies are conducted on the plant model Arabidopsis, but no or few information are available for important crop species, such as tomato (Solanum lycopersicum L.). In our study, we analyzed for the first time the endogenous CKs content in tomato hypocotyls during skotomorphogenesis, photomorphogenesis and de-etiolation. For this purpose, two tomato genotypes were used: cv. Rutgers (wild-type; WT) and its corresponding mutant (7B-1) affected in its responses to blue light (BL). Using physiological and molecular approaches, we identified that the skotomorphogenesis is characterized by an endoreduplication-mediated cell expansion, which is inhibited upon BL exposure as seen by the accumulation of trancripts encoding CycD3, key regulators of the cell cycle. Our study showed for the first time that iP (isopentenyladenine) is the CK accumulated in the tomato hypocotyl upon BL exposure, suggesting its specific role in photomorphogenesis. This result was supported by physiological experiments and gene expression data. We propose a common model to explain the role and the relationship between CKs, namely iP, and endoreduplication during de-etiolation and photomorphogenesis.

• MeSH
• buněčný cyklus účinky léků   genetika   MeSH
• cyklin D3 genetika   metabolismus   MeSH
• cytokininy metabolismus   MeSH
• endoreduplikace fyziologie   účinky záření   MeSH
• fylogeneze MeSH
• hypokotyl fyziologie   účinky záření   MeSH
• isopentenyladenosin metabolismus   MeSH
• morfogeneze fyziologie   účinky záření   MeSH
• ploidie MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• semenáček fyziologie   účinky záření   MeSH
• Solanum lycopersicum fyziologie   účinky záření   MeSH
• světlo MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cyklin D3 MeSH
• cytokininy MeSH
• isopentenyladenosin MeSH
• N(6)-(delta(2)-isopentenyl)adenine MeSH Prohlížeč
• rostlinné proteiny MeSH

BACKGROUND AND AIMS: Nitric oxide (NO) is involved in the signalling and regulation of plant growth and development and responses to biotic and abiotic stresses. The photoperiod-sensitive mutant 7B-1 in tomato (Solanum lycopersicum) showing abscisic acid (ABA) overproduction and blue light (BL)-specific tolerance to osmotic stress represents a valuable model to study the interaction between light, hormones and stress signalling. The role of NO as a regulator of seed germination and ABA-dependent responses to osmotic stress was explored in wild-type and 7B-1 tomato under white light (WL) and BL. METHODS: Germination data were obtained from the incubation of seeds on germinating media of different composition. Histochemical analysis of NO production in germinating seeds was performed by fluorescence microscopy using a cell-permeable NO probe, and endogenous ABA was analysed by mass spectrometry. KEY RESULTS: The NO donor S-nitrosoglutathione stimulated seed germination, whereas the NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) had an inhibitory effect. Under WL in both genotypes, PTIO strongly suppressed germination stimulated by fluridone, an ABA inhibitor. The stimulatory effect of the NO donor was also observed under osmotic stress for 7B-1 seeds under WL and BL. Seed germination inhibited by osmotic stress was restored by fluridone under WL, but less so under BL, in both genotypes. This effect of fluridone was further modulated by the NO donor and NO scavenger, but only to a minor extent. Fluorescence microscopy using the cell-permeable NO probe DAF-FM DA (4-amino-5-methylamino-2',7'-difluorofluorescein diacetate) revealed a higher level of NO in stressed 7B-1 compared with wild-type seeds. CONCLUSIONS: As well as defective BL signalling, the differential NO-dependent responses of the 7B-1 mutant are probably associated with its high endogenous ABA concentration and related impact on hormonal cross-talk in germinating seeds. These data confirm that light-controlled seed germination and stress responses include NO-dependent signalling.

• MeSH
• biologické modely MeSH
• cyklické N-oxidy farmakologie   MeSH
• donory oxidu dusnatého farmakologie   MeSH
• fluoresceiny analýza   MeSH
• fyziologický stres * účinky léků   účinky záření   MeSH
• imidazoly farmakologie   MeSH
• kinetika MeSH
• klíčení * účinky léků   účinky záření   MeSH
• kyselina abscisová metabolismus   MeSH
• mutace MeSH
• osmóza účinky léků   účinky záření   MeSH
• oxid dusnatý farmakologie   MeSH
• pyridony farmakologie   MeSH
• regulace genové exprese u rostlin účinky léků   účinky záření   MeSH
• regulátory růstu rostlin metabolismus   MeSH
• S-nitrosoglutathion farmakologie   MeSH
• scavengery volných radikálů farmakologie   MeSH
• semena rostlinná účinky léků   genetika   fyziologie   účinky záření   MeSH
• signální transdukce účinky léků   účinky záření   MeSH
• Solanum lycopersicum účinky léků   genetika   fyziologie   účinky záření   MeSH
• světlo * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide MeSH Prohlížeč
• 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate MeSH Prohlížeč
• cyklické N-oxidy MeSH
• donory oxidu dusnatého MeSH
• fluoresceiny MeSH
• fluridone MeSH Prohlížeč
• imidazoly MeSH
• kyselina abscisová MeSH
• oxid dusnatý MeSH
• pyridony MeSH
• regulátory růstu rostlin MeSH
• S-nitrosoglutathion MeSH
• scavengery volných radikálů MeSH