This study analyzed physiological and molecular characteristics associated with the resistance to aging or anti-senescence in Camellia oleifera Abel. Trees over 100 years old (ancient trees) were compared with those about 30 years old (mature trees). Total chlorophylls, chlorophyll a/b ratio, and hydrogen peroxide concentrations in ancient tree leaves were significantly higher than in their counterparts. Significantly higher activities of superoxide dismutase, peroxidase, and catalase were detected in ancient tree leaves. Nine Chl a/b-binding protein genes, 15 antioxidant enzyme genes, 21 hormone-related genes, and 301 stress-related genes were upregulated, and 42 protein-degradation genes were downregulated in ancient tree leaves. By increasing chlorophyll content and antioxidant enzyme activities and regulating the ageing-related genes expression, ancient C. oleifera leaves maintained remarkable vitality. Although further research is needed, our study may shed some light on how ancient C. oleifera trees can resist ageing and sustain their healthy growth.

• Klíčová slova
• Camellia oleifera, anti-ageing, anti-senescence, plant senescence,
• Publikační typ
• časopisecké články MeSH

The effectiveness of Methylobacterium symbioticum in maize and strawberry plants was measured under different doses of nitrogen fertilisation. The biostimulant effect of the bacteria was observed in maize and strawberry plants treated with the biological inoculant under different doses of nitrogen fertiliser compared to untreated plants (control). It was found that bacteria allowed a 50 and 25% decrease in the amount of nitrogen applied in maize and strawberry crops, respectively, and the photosynthetic capacity increased compared with the control plant under all nutritional conditions. A decrease in nitrate reductase activity in inoculated maize plants indicated that the bacteria affects the metabolism of the plant. In addition, inoculated strawberry plants grown with a 25% reduction in nitrogen had a higher concentration of nitrogen in leaves than control plants under optimal nutritional conditions. Again, this indicates that Methylobacterium symbioticum provide an additional supply of nitrogen.

• Klíčová slova
• Biofertiliser, Biostimulant, Maize, Methylobacterium symbioticum, Nitrogen-fixing bacteria, Strawberry,
• MeSH
• dusík metabolismus   MeSH
• fotosyntéza MeSH
• jahodník * metabolismus   MeSH
• kukuřice setá mikrobiologie   MeSH
• Methylobacterium * metabolismus   MeSH
• zemědělské plodiny MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• dusík MeSH

Leaf senescence can be induced by stress or aging, sometimes in a synergistic manner. It is generally acknowledged that the ability to withstand senescence-inducing conditions can provide plants with stress resilience. Although the signaling and transcriptional networks responsible for a delayed senescence phenotype, often referred to as a functional stay-green trait, have been actively investigated, very little is known about the subsequent metabolic adjustments conferring this aptitude to survival. First, using the individually darkened leaf (IDL) experimental setup, we compared IDLs of wild-type (WT) Arabidopsis (Arabidopsis thaliana) to several stay-green contexts, that is IDLs of two functional stay-green mutant lines, oresara1-2 (ore1-2) and an allele of phytochrome-interacting factor 5 (pif5), as well as to leaves from a WT plant entirely darkened (DP). We provide compelling evidence that arginine and ornithine, which accumulate in all stay-green contexts-likely due to the lack of induction of amino acids (AAs) transport-can delay the progression of senescence by fueling the Krebs cycle or the production of polyamines (PAs). Secondly, we show that the conversion of putrescine to spermidine (SPD) is controlled in an age-dependent manner. Thirdly, we demonstrate that SPD represses senescence via interference with ethylene signaling by stabilizing the ETHYLENE BINDING FACTOR1 and 2 (EBF1/2) complex. Taken together, our results identify arginine and ornithine as central metabolites influencing the stress- and age-dependent progression of leaf senescence. We propose that the regulatory loop between the pace of the AA export and the progression of leaf senescence provides the plant with a mechanism to fine-tune the induction of cell death in leaves, which, if triggered unnecessarily, can impede nutrient remobilization and thus plant growth and survival.

• MeSH
• Arabidopsis * metabolismus   MeSH
• arginin metabolismus   MeSH
• ethyleny metabolismus   MeSH
• listy rostlin metabolismus   MeSH
• ornithin genetika   metabolismus   MeSH
• proteiny huseníčku * metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• senescence rostlin MeSH
• transkripční faktory metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• arginin MeSH
• ethyleny MeSH
• ornithin MeSH
• proteiny huseníčku * MeSH
• transkripční faktory MeSH

Magnesium (Mg2+) is a macronutrient involved in essential cellular processes. Its deficiency or excess is a stress factor for plants, seriously affecting their growth and development and therefore, its accurate regulation is essential. Recently, we discovered that phospholipase Dα1 (PLDα1) activity is vital in the stress response to high-magnesium conditions in Arabidopsis roots. This study shows that PLDα1 acts as a negative regulator of high-Mg2+-induced leaf senescence in Arabidopsis. The level of phosphatidic acid produced by PLDα1 and the amount of PLDα1 in the leaves increase in plants treated with high Mg2+. A knockout mutant of PLDα1 (pldα1-1), exhibits premature leaf senescence under high-Mg2+ conditions. In pldα1-1 plants, higher accumulation of abscisic and jasmonic acid (JA) and impaired magnesium, potassium and phosphate homeostasis were observed under high-Mg2+ conditions. High Mg2+ also led to an increase of starch and proline content in Arabidopsis plants. While the starch content was higher in pldα1-1 plants, proline content was significantly lower in pldα1-1 compared with wild type plants. Our results show that PLDα1 is essential for Arabidopsis plants to cope with the pleiotropic effects of high-Mg2+ stress and delay the leaf senescence.

• Klíčová slova
• Arabidopsis thaliana, abscisic acid, jasmonic acid, leaf senescence, magnesium homeostasis, phospholipase D, proline, starch,
• Publikační typ
• časopisecké články MeSH

Leaf senescence is a highly regulated final phase of leaf development preceding massive cell death. It results in the coordinated degradation of macromolecules and the subsequent nutrient relocation to other plant parts. Very little is still known about early stages of leaf senescence during normal leaf ontogeny that is not triggered by stress factors. This paper comprises an integrated study of natural leaf senescence in tobacco plants grown in vitro, using molecular, structural, and physiological information. We determined the time sequence of ultrastructural changes in mesophyll cells during leaf senescence, showing that the degradation of chloroplast ultrastructure fully correlated with changes in chlorophyll content. The earliest degenerative changes in chloroplast ultrastructure coinciding with early chromatin condensation were observed already in mature green leaves. A continuum of degradative changes in chloroplast ultrastructure, chromatin condensation and aggregation, along with progressive decrease in cytoplasm organization and electron density were observed in the course of mesophyll cells ageing. Although the total amounts of endogenous cytokinins gradually increased during leaf ontogenesis, the proportion of bioactive cytokinin forms, as well as their phosphate precursors, in total cytokinin content rapidly declined with ageing. Endogenous indole-3-acetic acid (IAA) levels were strongly reduced in senescent leaves, and a decreasing tendency was also observed for abscisic acid (ABA) levels. Senescence-associated tobacco cysteine proteases (CP, E.C. 3.4.22) CP1 and CP23 genes were induced in the initial phase of senescence. Genes encoding glutamate dehydrogenase (GDH, E.C. 1.4.1.2) and one isoform of cytosolic glutamine synthetase (GS1, E.C. 6.3.1.2) were induced in the late stage of senescence, while chloroplastic GS (GS2) gene showed a continuous decrease with leaf ageing.

• Klíčová slova
• Leaf senescence, Mesophyll ultrastructure, Phytohormones, Tobacco, qRT-PCR,
• MeSH
• buněčná smrt MeSH
• chlorofyl metabolismus   MeSH
• cytokininy metabolismus   MeSH
• exprese genu MeSH
• listy rostlin cytologie   růst a vývoj   metabolismus   MeSH
• metabolické sítě a dráhy MeSH
• mezofylové buňky fyziologie   ultrastruktura   MeSH
• regulátory růstu rostlin metabolismus   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• stárnutí buněk MeSH
• stárnutí MeSH
• tabák cytologie   růst a vývoj   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chlorofyl MeSH
• cytokininy MeSH
• regulátory růstu rostlin MeSH
• rostlinné proteiny MeSH

Annexins are a family of calcium- and membrane-binding proteins that are important for plant tolerance to adverse environmental conditions. Annexins function to counteract oxidative stress, maintain cell redox homeostasis, and enhance drought tolerance. In the present study, an endogenous annexin, STANN1, was overexpressed to determine whether crop yields could be improved in potato (Solanum tuberosum L.) during drought. Nine potential potato annexins were identified and their expression characterized in response to drought treatment. STANN1 mRNA was constitutively expressed at a high level and drought treatment strongly increased transcription levels. Therefore, STANN1 was selected for overexpression analysis. Under drought conditions, transgenic potato plants ectopically expressing STANN1 were more tolerant to water deficit in the root zone, preserved more water in green tissues, maintained chloroplast functions, and had higher accumulation of chlorophyll b and xanthophylls (especially zeaxanthin) than wild type (WT). Drought-induced reductions in the maximum efficiency and the electron transport rate of photosystem II (PSII), as well as the quantum yield of photosynthesis, were less pronounced in transgenic plants overexpressing STANN1 than in the WT. This conferred more efficient non-photochemical energy dissipation in the outer antennae of PSII and probably more efficient protection of reaction centers against photooxidative damage in transgenic plants under drought conditions. Consequently, these plants were able to maintain effective photosynthesis during drought, which resulted in greater productivity than WT plants despite water scarcity. Although the mechanisms underlying this stress protection are not yet clear, annexin-mediated photoprotection is probably linked to protection against light-induced oxidative stress.

• MeSH
• annexiny genetika   metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• fotosyntéza MeSH
• fotosystém II - proteinový komplex metabolismus   MeSH
• fyziologický stres MeSH
• geneticky modifikované rostliny MeSH
• období sucha MeSH
• oxidační stres MeSH
• regulace genové exprese u rostlin MeSH
• rekombinantní proteiny genetika   metabolismus   MeSH
• rostlinné geny MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• Solanum tuberosum genetika   růst a vývoj   metabolismus   MeSH
• světlo MeSH
• xanthofyly metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• annexiny MeSH
• chlorofyl MeSH
• fotosystém II - proteinový komplex MeSH
• rekombinantní proteiny MeSH
• rostlinné proteiny MeSH
• xanthofyly MeSH

Nitrogen (N) efficiency of winter oilseed rape (Brassica napus L.) line-cultivars (cvs.), defined as high grain yield under N limitation, has been primarily attributed to maintained N uptake during reproductive growth (N uptake efficiency) in combination with delayed senescence of the older leaves accompanied with maintained photosynthetic capacity (functional stay-green). However, it is not clear whether genotypic variation in N starvation-induced leaf senescence is due to leaf-inherent factors and/or governed by root-mediated signals. Therefore, the N-efficient and stay-green cvs. NPZ-1 and Apex were reciprocally grafted with the N-inefficient and early-senescing cvs. NPZ-2 and Capitol, respectively and grown in hydroponics. The senescence status of older leaves after 12 days of N starvation assessed by SPAD, photosynthesis and the expression of the senescence-specific cysteine protease gene SAG12-1 revealed that the stay-green phenotype of the cvs. NPZ-1 and Apex under N starvation was primarily under the control of leaf-inherent factors. The same four cultivars were submitted to N starvation for up to 12 days in a time-course experiment. The specific leaf contents of biologically active and inactive cytokinins (CKs) and the expression of genes involved in CK homeostasis revealed that under N starvation leaves of early-senescing cultivars were characterized by inactivation of biologically active CKs, whereas in stay-green cultivars synthesis, activation, binding of and response to biologically active CKs were favoured. These results suggest that the homeostasis of biologically active CKs was the predominant leaf-inherent factor for cultivar differences in N starvation-induced leaf senescence and thus N efficiency.

• Klíčová slova
• Brassica napus, cytokinins, genotypic differences, leaf senescence, nitrogen efficiency, nitrogen starvation, reciprocal grafting, stay-green.,
• MeSH
• Brassica napus genetika   metabolismus   MeSH
• chlorofyl metabolismus   MeSH
• cytokininy metabolismus   MeSH
• dusík metabolismus   MeSH
• fotosyntéza MeSH
• glukosidy metabolismus   MeSH
• homeostáza MeSH
• kořeny rostlin metabolismus   MeSH
• listy rostlin enzymologie   růst a vývoj   metabolismus   MeSH
• proteasy metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• roční období * MeSH
• rostlinné geny MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• signální transdukce genetika   MeSH
• zeatin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chlorofyl MeSH
• cytokininy MeSH
• dusík MeSH
• glukosidy MeSH
• proteasy MeSH
• rostlinné proteiny MeSH
• zeatin-O-glucoside MeSH Prohlížeč
• zeatin MeSH

Arabidopsis (Arabidopsis thaliana) leaf development relies on subsequent phases of cell proliferation and cell expansion. During the proliferation phase, chloroplasts need to divide extensively, and during the transition from cell proliferation to expansion, they differentiate into photosynthetically active chloroplasts, providing the plant with energy. The transcription factor GROWTH REGULATING FACTOR5 (GRF5) promotes the duration of the cell proliferation period during leaf development. Here, it is shown that GRF5 also stimulates chloroplast division, resulting in a higher chloroplast number per cell with a concomitant increase in chlorophyll levels in 35S:GRF5 leaves, which can sustain higher rates of photosynthesis. Moreover, 35S:GRF5 plants show delayed leaf senescence and are more tolerant for growth on nitrogen-depleted medium. Cytokinins also stimulate leaf growth in part by extending the cell proliferation phase, simultaneously delaying the onset of the cell expansion phase. In addition, cytokinins are known to be involved in chloroplast development, nitrogen signaling, and senescence. Evidence is provided that GRF5 and cytokinins synergistically enhance cell division and chlorophyll retention after dark-induced senescence, which suggests that they also cooperate to stimulate chloroplast division and nitrogen assimilation. Taken together with the increased leaf size, ectopic expression of GRF5 has great potential to improve plant productivity.

• MeSH
• Arabidopsis účinky léků   genetika   fyziologie   MeSH
• buněčné dělení účinky léků   MeSH
• chlorofyl metabolismus   MeSH
• chloroplasty účinky léků   metabolismus   ultrastruktura   MeSH
• cytokininy farmakologie   MeSH
• dusík nedostatek   MeSH
• fotosyntéza * účinky léků   MeSH
• geneticky modifikované rostliny MeSH
• listy rostlin účinky léků   růst a vývoj   fyziologie   ultrastruktura   MeSH
• proteiny 14-3-3 genetika   metabolismus   MeSH
• regulace genové exprese u rostlin účinky léků   MeSH
• rostlinné geny MeSH
• trans-aktivátory genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chlorofyl MeSH
• cytokininy MeSH
• dusík MeSH
• GRF5 protein, Arabidopsis MeSH Prohlížeč
• proteiny 14-3-3 MeSH
• trans-aktivátory MeSH