Purification and characterization of a thiol-protease induced during senescence of unpollinated ovaries of Pisum sativum

A senescence-specific protease has been purified from senescent unpollinated ovaries of Pisum sativum L. cv. Alaska by acidic extraction. (NH₄)₂SO₄ fractionation, ion exchange chromatography on CM-Sephadex, and affinity chromatography on ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco)-Sepharose. Characterization of the purified protease indicated that it is a thiol-endoprotease (EC 3. 4. 22 class) active over a wide pH range. Purified antibodies against this protease inhibit the degradation of Rubisco in autodigested extracts of senescent ovaries, suggesting that Rubisco might be a substrate for the protease in senescent pea ovaries. The relative levels of the protease were determined by an enzyme-linked immunosorbent assay (ELISA) along the processes of ovary senescence and gibberellic acid (GA)-induced fruit development, indicating its induction at the beginning of senescence and the suppression of its synthesis by GA treatment.     

Use of lysophosphatidylethanolamine, a natural lipid, to retard tomato leaf and fruit senescence

We studied the influence of lysophosphatidylethanolamine (LPE) on the pattern and rate of ethylene production and respiration of tomato ( Lycopersicon esculentum cv. H7155) leaflets and fruit. Leaflets that had been senescing on the plant showed a climacteric-like rise in ethylene production but not in respiration rate which decreased continuously with leaf age. Detached leaflets had a climacteric-like pattern in respiration whether they were incubated in complete darkness or in light. Detached leaflets incubated in the dark had higher rates of ethylene production and CO₂ evolution than did light-incubated leaves. There was no change in the pattern of ethylene production or CO₂ evolution as a result of LPE treatment. However, LPE-treated attached and detached leaflets had consistently lower rates of CO₂ evolution. The reduction in CO₂ evolution by LPE was most pronounced at the climacteric-like peak of the detached leaves. LPE-treated leaflets had a higher chlorophyll content and fresh weight and lower electrolyte leakage than the control. LPE-treated fruits had lower rates of ethylene and CO₂ production than did the control. LPE-treated fruits also had higher pericarp firmness and lower electrolyte leakage than the control. The results of the present study provide evidence that LPE is able to retard senescence of attached leaves and detached leaves and tomato fruits. Several recent studies suggest that lysolipids can act in a specific manner as metabolic regulators. Our results suggest a specific role of lysolipid LPE in aging and senescence     

Role of other plant organs in gibberellic acid-induced delay of leaf senescence in alstroemeria cut flowers

Chlorophyll loss in leaves of cut flowers of alstroemeria (Alstroemeria pelegrina L. cv. Westland) was rapid in darkness and counteracted by irradiation and treatment of the flowers with gibberellic acid (GA₃). The mechanism of the effect of GA₃ under dark conditions was investigated. The content of various carbohydrates in the leaves under dark conditions rapidly decreased; this was not influenced by treatment with GA_3. indicating that the loss of carbohydrates in the leaves did not induce the loss of chlorophyll. Placing the cut flowers in various solutions of organic and inorganic nutrients exhibited no significant effect on the retention of chlorophyll in leaves of dark-senescing flowers. The total nitrogen content in leaves of dark-senescing cut flowers decreased with time. Leaves of GA₃-treated flowers retained more nitrogen. In contrast, the buds of GA₃-treated flowers retained less nitrogen during senescence in the dark than control buds. To investigate whether GA₃ affects export of assimilates from the leaf to various parts of control and GA₃-treated flowers, we labelled one leaf with radioactive carbon dioxide. ¹⁴C-assimilates accumulated preferentially in the flowers, in which the relative specific activity of the youngest floral buds was highest. No significant differences were observed in the distribution of ¹⁴C-labelled compounds between the buds of control and GA₃-treated flowers. To establish the importance of source-sink relations for the loss of leaf chlorophyll we removed the flower buds (i. e. the strongest sink) from the cut flowers. This removal only slightly delayed chlorophyll loss as compared to the large delay caused by GA₃-treatment. In addition, detached leaf tips exhibited chlorophyll loss in the dark, which was delayed by GA₃-treatment in a fashion comparable with that in flowers. Together these data demonstrate that interactions of the leaves with other plant organs are not essential for chlorophyll loss during senescence in the dark. Additionally, we have found no evidence that GA₃ delays the loss of chlorophyll by affecting the transport of nutrients within the cut flowers.     

Effects of light and regulators on senescence-related changes in soluble proteins in detached oat (Avena sativa L.) leaves

The rate of senescence and the two-dimensional pattern of soluble proteins from detached oat leaves senescing in either darkness or light were analyzed, and compared to those of leaves in which senescence was delayed by application of the cytokinin benzyladenine or enhanced through the action of abscisic acid.Senescence of detached leaves in light did not differ significantly from senescence in attached leaves on intact plants. In darkness, protein was lost at a higher rate than in light, but several individual proteins showed relative increases. Notably, proteins previously characterized as high-molecular-weight proteins and senescence-associated proteins (Klerk et al., 1992) increased. Changes observed during incubation in light or darkness appeared to be related to this condition rather than the rate or progress of senescence. Cytokinins delayed and abscisic acid accelerated the changes in protein pattern compared to water. Beside changes previously identified in leaves senescing on the plant, detached leaves show alterations that reflect their condition of incubation rather than their developmental progress.Abbreviations 2D-PAG two-dimensional polyacrylamide gel electrophoresis - ABA abscisic acid - BA N⁶-benzyladenine - BSA bovine serum albumin - EDTA ethylenediamine tetraacetic acid - IEF isoelectric focusing - Rubisco ribulosebisphosphate carboxylase/oxygenase - SDS sodium dodecyl sulfate - Tris tris (hydroxymethyl) aminomethane     

渍水对冬小麦生长的危害及其生理效应

小麦受渍后叶片的光合和蒸腾速率迅速下降,而后则显微弱的回升趋势。渍害不仅削弱小麦光合产物的积累,并且改变光合产物在地上部分和根系中的分配比例;植株根／冠比下降,而黄叶的发展与根／冠比的变化呈显著负相关;渍害改变小麦的发育进程,尤其是后期渍害明显促使小麦早衰。认为清水使叶片光合速率降低、光合有效面积损失和衰老加速,从而危害小麦的生长。     

Evolutionary senescence in plants

Senescence is a decline in age-specific survival and reproduction with advancing age. Studies of evolutionary plant senescence are designed to explain this decline in life history components within the context of natural selection. A review of studies of plant demography reveals senescent declines in both annual and perennial plants, but also suggests that there are some plant species which may not be expected to show senescence. Thus, future comparative studies of closely related species, with and without senescence, should be possible. The assumptions of the major evolutionary theories of senescence are evaluated for their validity with respect to plants. Different plant species violate one or more of the assumptions of the theories, yet the consequences of violating these assumptions have never been investigated. Whereas, to date, evolutionary senescence has been studied only indirectly in plants, it is concluded that plants provide good experimental systems for clarifying our understanding of senescence in natural populations.     

Evolution of aging: Testing the theory usingDrosophila

Evolutionary explanations of aging (or senescence) fall into two classes. First, organisms might have evolved the optimal life history, in which survival and fertility late in life are sacrificed for the sake of early reproduction or high pre-adult survival. Second, the life history might be depressed below this optimal compromise by the influx of deleterious mutations; since selection against late-acting mutations is weaker, deleterious mutations will impose a greater load on late life. We discuss ways in which these theories might be investigated and distinguished, with reference to experimental work withDrosophila. While genetic correlations between life history traits determine the immediate response to selection, they are hard to measure, and may not reflect the fundamental constraints on life history. Long term selection experiments are more likely to be informative. The third approach of using experimental manipulations suffers from some of the same problems as measures of genetic correlations; however, these two approaches may be fruitful when used together. The experimental results so far suggest that aging inDrosophila has evolved in part as a consequence of selection for an optimal life history, and in part as a result of accumulation of predominantly late-acting deleterious mutations. Quantification of these effects presents a major challenge for the future.     

Abundance of white lace lerp psyllids on understorey and canopy river red gums and relationships with foliar sugars and tannins

1. Trees present herbivorous insects with the greatest diversity of resources of any plant growth form. Both ontogeny and shading can alter suitability for arboreal insect herbivores. 2. We conducted a longitudinal study of tagged ‘mature’ (>12 months old) Eucalyptus camaldulensis leaves to compare the suitability of understorey and canopy trees for the leaf senescence-inducing psyllid, Cardiaspina albitextura. We quantified sugars and tannins as possible predictors of nymphal abundance. 3. Canopy leaves hosted double the number of nymphs as understorey leaves. Variation among individual trees (understorey and canopy) was the most important source of heterogeneity explaining psyllid abundance, although relative leaf age significantly influenced oviposition on canopy leaves. The diversity of foliar sugars was higher among canopy leaves than among understorey leaves. There was significant between-tree diversity in total hydrolysable tannins (HTs) and total condensed tannins (CTs) among understorey trees but not among canopy trees. Heterogeneity among understorey and canopy trees was explained by greater diversity of ellagitannins (HTs) than of CTs. 4. Shading is detrimental to the survival of nymphs on both host types, but sugars are unlikely to explain variation in suitability. Vescalagin (an ellagitannin) was negatively correlated with the abundance of nymphs on both host types.     

Cellular expansion of MSCs: Shifting the regenerative potential

Mesenchymal-derived stromal or progenitor cells, commonly called “MSCs,” have attracted significant clinical interest for their remarkable abilities to promote tissue regeneration and reduce inflammation. Recent studies have shown that MSCs' therapeutic effects, originally attributed to the cells' direct differentiation capacity into the tissue of interest, are largely driven by the biomolecules the cells secrete, including cytokines, chemokines, growth factors, and extracellular vesicles containing miRNA. This secretome coordinates upregulation of endogenous repair and immunomodulation in the local microenvironment through crosstalk of MSCs with host tissue cells. Therapeutic applications for MSCs and their secretome-derived products often involve in vitro monolayer expansion. However, consecutive passaging of MSCs significantly alters their therapeutic potential, inducing a broad shift from a pro-regenerative to a pro-inflammatory phenotype. A consistent by-product of in vitro expansion of MSCs is the onset of replicative senescence, a state of cell arrest characterized by an increased release of proinflammatory cytokines and growth factors. However, little is known about changes in the secretome profile at different stages of in vitro expansion. Some culture conditions and bioprocessing techniques have shown promise in more effectively retaining the pro-regenerative and anti-inflammatory MSC phenotype throughout expansion. Understanding how in vitro expansion conditions influence the nature and function of MSCs, and their associated secretome, may provide key insights into the underlying mechanisms driving these alterations. Elucidating the dynamic and diverse changes in the MSC secretome at each stage of in vitro expansion is a critical next step in the development of standardized, safe, and effective MSC-based therapies.     

Deciphering RNA m6A regulation in aging: Perspectives on current advances and future directions

N⁶-methyladenosine (m⁶A) is a dynamic and reversible RNA modification that has emerged as a crucial player in the life cycle of RNA, thus playing a pivotal role in various biological processes. In recent years, the potential involvement of RNA m⁶A modification in aging and age-related diseases has gained increasing attention, making it a promising target for understanding the molecular mechanisms underlying aging and developing new therapeutic strategies. This Perspective article will summarize the current advances in aging-related m⁶A regulation, highlighting the most significant findings and their implications for our understanding of cellular senescence and aging, and the potential for targeting RNA m⁶A regulation as a therapeutic strategy. We will also discuss the limitations and challenges in this field and provide insights into future research directions. By providing a comprehensive overview of the current state of the field, this Perspective article aims to facilitate further advances in our understanding of the molecular mechanisms underlying aging and to identify new therapeutic targets for aging-related diseases.