Leaf Senescence Research Articles

Scaffold protein RACK1A positively regulates leaf senescence by coordinating the EIN3-miR164-ORE1 transcriptional cascade in Arabidopsis.

Plants have adopted versatile scaffold proteins to facilitate the crosstalk between multiple signaling pathways. Leaf senescence is a well-programmed developmental stage that is coordinated by various external and internal signals. However, the functions of plant scaffold proteins in response to senescence signals are not well understood. Here, we report that the scaffold protein RACK1A (RECEPTOR FOR ACTIVATED C KINASE 1 A) participates in leaf senescence mediated by ethylene signaling via the coordination of the EIN3-miR164-ORE1 transcriptional regulatory cascade. RACK1A is a novel positive regulator of ethylene-mediated leaf senescence. The rack1a mutant exhibits delayed leaf senescence, whilst transgenic lines overexpressing RACK1A display early leaf senescence. Moreover, RACK1A promotes EIN3 protein accumulation, and directly interacts with EIN3 (ETHYLENE INSENSITIVE 3) to enhance its DNA-binding activity. Together, they then associate with the miR164 promoter to inhibit its transcription, leading to the release of the inhibition on downstream ORE1 (ORESARA 1) transcription and the promotion of leaf senescence. This study reveals a mechanistic framework by which RACK1A promotes leaf senescence via the EIN3-miR164-ORE1 transcriptional cascade, and provides a paradigm for how scaffold proteins finely tune phytohormone signaling to control plant development. This article is protected by copyright. All rights reserved.

Phenology advances uniformly in spring but diverges in autumn among three temperate tree species in response to warming

Predicting the length of growing season to further warming relies on both spring and autumn phenological responses of different species, but with little experimental evidence under different levels of warming. Here, the timing of spring phenology including budburst and leaf unfolding, and autumn phenology including leaf coloration and leaf fall, were examined in 2-year-old seedlings of three temperate tree species (Fraxinus mandschurica, Quercus mongolica, and Juglans mandshurica) that were grown in the field under warming conditions (W0, ambient; W2, +2°C; W4, +4°C). Our study showed that warming advanced budburst and leaf unfolding by 9 and 8 days in the W2 treatments and by 13 and 15 days in the W4 treatments, respectively, with the magnitude varied greatly among species. However, we found a delayed autumn leaf senescence only for Q. mongolica, for which leaf coloration and leaf fall delayed by 19 and 6 days and by 17 and 12 days in the W2 and W4 treatments, respectively. The temperature sensitivity of budburst declined with increasing temperature in Q. mongolica. The growing season was extended by 7–18 and 10–25 days in W2 and W4, primarily through the advancement of spring phenology. Warming increased budburst synchrony, such that J. mandshurica, which typically has the earliest leaf emergence, lost its growth and competitive advantages over the more phenologically plastic species, F. mandschurica and Q. mongolica. Our results provide new insights into the effects of elevated temperatures on phenological shifts and their potential influences on tree species recruitment and forest structure and composition.

Abscisic acid in plants under abiotic stress: crosstalk with major phytohormones

Extensive crosstalk exists among ABA and different phytohormones that modulate plant tolerance against different abiotic stress. Being sessile, plants are exposed to a wide range of abiotic stress (drought, heat, cold, salinity and metal toxicity) that exert unwarranted threat to plant life and drastically affect growth, development, metabolism, and yield of crops. To cope with such harsh conditions, plants have developed a wide range of protective phytohormones of which abscisic acid plays a pivotal role. It controls various physiological processes of plants such as leaf senescence, seed dormancy, stomatal closure, fruit ripening, and other stress-related functions. Under challenging situations, physiological responses of ABA manifested in the form of morphological, cytological, and anatomical alterations arise as a result of synergistic or antagonistic interaction with multiple phytohormones. This review provides new insight into ABA homeostasis and its perception and signaling crosstalk with other phytohormones at both molecular and physiological level under critical conditions including drought, salinity, heavy metal toxicity, and extreme temperature. The review also reveals the role of ABA in the regulation of various physiological processes via its positive or negative crosstalk with phytohormones, viz., gibberellin, melatonin, cytokinin, auxin, salicylic acid, jasmonic acid, ethylene, brassinosteroids, and strigolactone in response to alteration of environmental conditions. This review forms a basis for designing of plants that will have an enhanced tolerance capability against different abiotic stress.

Combination of suitable planting density and nitrogen rate for high yield maize and their source-sink relationship in Northwest China.

Increasing crop yield per unit area by increasing planting density is essential to ensure food security. However, the optimal combination of planting density and N application for high-yielding maize and its source-sink characteristics need to be more clearly understood. A two-year field experiment was conducted combining three planting densities (D1: 70,000 plants ha-1 ；D2: 100,000 plants ha-1 ；D3: 130,000 plants ha-1 ) and three nitrogen rates (N1: 150 kg N hm-2 , N2: 350 kg N hm-2 , N3: 450 kg N hm-2 ). The results showed that increasing planting density significantly increased leaf area index and grain yield, but negatively affected ear traits. The Richards model was used to fit the dynamic changes of dry matter accumulation of maize under different treatments, and the fitting results were good. Increasing planting density increased population yield while limiting the development of individual plants, bringing the period of rapid dry matter accumulation to an early end and accelerating leaf senescence. Appropriate N rate could prolong the period of rapid accumulation of dry matter in maize, increase the 100-kernel weight. Increasing planting density enhanced post-silking dry matter accumulation to a lesser extent, and the source-sink relationship of the maize population gradually developed from sink limitation to source limitation with increasing planting density. The decrease in yield due to the insufficient source strength to meet the sink demand at too high densities was the reason that limited further improvement of the optimal planting density. Appropriate N rate facilitated the realization of yield potential at high density. This article is protected by copyright. All rights reserved.

Forage productivity and morphogenesis of Trachypogon vestitus as affected by phosphate fertilization levels in the Roraima’s savannas

The effects of phosphate fertilization (0, 40, 80 and 120 kg of P2O5 ha-1) on forage production and morphogenetic and structural characteristics of Trachypogon vestitus pastures were evaluated under natural field conditions in the savannas of Roraima. Phosphate fertilization positively and significantly (P<0.05) affected green dry matter (GDM) production, absolute growth rate (AGR), number of tillers plant-1, number of leaves tiller-1 (NLT), average leaf size (ALS), leaf tiller area (LTA), appearance rates (LAR), expansion (LER) and leaf senescence rates. The maximum yields of GDM, AGR, LAR, LER, NLT, LTA and ALS were obtained with the application of 109.2; 106.4; 56.1; 81.5; 97.4; 58.6 and 63.7 kg of P2O5 ha-1, respectively. The efficiency of P utilization was inversely proportional to the P doses applied.

Domesticating Vigna stipulacea: Chromosome-Level genome assembly reveals VsPSAT1 as a candidate gene decreasing hard-seededness.

To increase food production under the challenges presented by global climate change, the concept of de novo domestication-utilizing stress-tolerant wild species as new crops-has recently gained considerable attention. We had previously identified mutants with desired domestication traits in a mutagenized population of the legume Vigna stipulacea Kuntze (minni payaru) as a pilot for de novo domestication. Given that there are multiple stress-tolerant wild legume species, it is important to establish efficient domestication processes using reverse genetics and identify the genes responsible for domestication traits. In this study, we identified VsPSAT1 as the candidate gene responsible for decreased hard-seededness, using a Vigna stipulacea isi2 mutant that takes up water from the lens groove. Scanning electron microscopy and computed tomography revealed that the isi2 mutant has lesser honeycomb-like wax sealing the lens groove than the wild-type, and takes up water from the lens groove. We also identified the pleiotropic effects of the isi2 mutant: accelerating leaf senescence, increasing seed size, and decreasing numbers of seeds per pod. While doing so, we produced a V. stipulacea whole-genome assembly of 441 Mbp in 11 chromosomes and 30,963 annotated protein-coding sequences. This study highlights the importance of wild legumes, especially those of the genus Vigna with pre-existing tolerance to biotic and abiotic stresses, for global food security during climate change.

Morphological and Physiological Mechanisms of Melatonin on Delaying Drought-Induced Leaf Senescence in Cotton.

Leaf senescence reduces the photosynthetic capacity of leaves, thus significantly affecting the growth, development, and yield formation of cotton. Melatonin (MT) is a multipotent substance proven to delay leaf senescence. However, its potential mechanism in delaying leaf senescence induced by abiotic stress remains unclear. This study aimed to explore the effect of MT on delaying drought-induced leaf senescence in cotton seedlings and to clarify its morphological and physiological mechanisms. Drought stress upregulated the leaf senescence marker genes, destroyed the photosystem, and led to excessive accumulation of reactive oxygen species (ROS, e.g., H2O2 and O2-), thus accelerating leaf senescence. However, leaf senescence was significantly delayed when 100 μM MT was sprayed on the leaves of the cotton seedlings. The delay was embodied by the increased chlorophyll content, photosynthetic capacity, and antioxidant enzyme activities, as well as decreased H2O2, O2-, and abscisic acid (ABA) contents by 34.44%, 37.68%, and 29.32%, respectively. MT significantly down-regulated chlorophyll degradation-related genes and senescence marker genes (GhNAC12 and GhWRKY27/71). In addition, MT reduced the chloroplast damage caused by drought-induced leaf senescence and maintained the integrity of the chloroplast lamellae structure under drought stress. The findings of this study collectively suggest that MT can effectively enhance the antioxidant enzyme system, improve photosynthetic efficiency, reduce chlorophyll degradation and ROS accumulation, and inhibit ABA synthesis, thereby delaying drought-induced leaf senescence in cotton.

Genome‐scale transcriptomic insights into the mature growth dynamic of tobacco leaves

AbstractThe harvest time is a key factor for cigar leaves with high quality, which varies greatly depending on the environment. In this study, we performed a growth characterization of the cigar tobacco CX‐26 (Nicotiana tabacum L.) from the cluster stage to the vigorous stage and mature stage. Further, soil plant analysis development measurement of three middle leaves with 67 (T1), 71 (T2), and 75 days (T3) of growth after transplant indicates that the maturity might change from 71 to 75 days of growth. A genome‐scale transcriptome was conducted to explore the gene expression dynamics of this maturity change. A total of 80,502 genes were detected in the CX‐26 leaves, of which 64,611 genes were annotated on the reference genome. T1 and T2 leaves had fewer differential expressing genes (DEGs), while T3 leaves had 26,456 DEGs from T2 leaves, supporting the distinct growth of T3 leaves. Analyses of Gene ontology, Kyoto encyclopedia of genes and genomes identified that DEGs are involved inkey pathways including photosynthesis‐antenna proteins, plant hormone/mitogen‐activated protein kinase signaling pathway, and plant‐pathogen interaction. Abscisic acid and jasmonate acids positively regulate leaf senescence and chlorophyll degradation and were higher in the T3 leaves compared with T1 and T2 leaves. In contrast, the total sugar was reduced in T3 leaves compared with T1 and T2 leaves, indicating the overripe state of the T3 leaves. Furthermore, several photosynthesis‐related enzymes and a transcription factor were highlighted in the gene regulatory network, which might regulate the dynamics of carbohydrate metabolism, lipid metabolism, and energy metabolism. In summary, our study provides insight into the growth state of CX‐26 cigar leaves.

Retracted] FAM172A modulates apoptosis and proliferation of colon cancer cells via STAT1 binding to its promoter.

Following the publication of this paper, it was drawn to the Editor's attention by a concerned reader that lanes 1‑3 of the EMSA results shown in Fig.6 on p.1278 were strikingly similar to data that had already appeared in a different form in the following publication by different authors at different research institutes: QiuK, Li Z, Chen J, Wu S, Zhu X, GaoS, GaoJ, Ren G and Zhou X: EIN3 and ORE1 accelerate degreening during ethylene‑mediated leaf senescence by directly activating chlorophyll catabolic genes in Arabidopsis. PLoS Genet11: e1005399, 2015. Owing to the fact that the contentious data in the above article had already been published prior to its submission to Oncology Reports, the Editor has decided that this paper should be retracted from the Journal. After having been in contact with the authors, they accepted the decision to retract the paper. The Editor apologizes to the readership for any inconvenience caused. [Oncology Reports 35: 1273‑1280, 2016; DOI: 10.3892/or.2015.4485.

Observations of biogenic volatile organic compounds over a mixed temperate forest during the summer to autumn transition

Abstract. The exchange of trace gases between the biosphere and the atmosphere is an important process that controls both chemical and physical properties of the atmosphere with implications for air quality and climate change. The terrestrial biosphere is a major source of reactive biogenic volatile organic compounds (BVOCs) that govern atmospheric concentrations of the hydroxy radical (OH) and ozone (O3) and control the formation and growth of secondary organic aerosol (SOA). Common simulations of BVOC surface–atmosphere exchange in chemical transport models use parameterizations derived from the growing season and do not consider potential changes in emissions during seasonal transitions. Here, we use observations of BVOCs over a mixed temperate forest in northern Wisconsin during broadleaf senescence to better understand the effects of the seasonal changes in canopy conditions (e.g., temperature, sunlight, leaf area, and leaf stage) on net BVOC exchange. The BVOCs investigated here include the terpenoids isoprene (C5H8), monoterpenes (MTs; C10H16), a monoterpene oxide (C10H16O), and sesquiterpenes (SQTs; C15H24), as well as a subset of other monoterpene oxides and dimethyl sulfide (DMS). During this period, MTs were primarily composed of α-pinene, β-pinene, and camphene, with α-pinene and camphene dominant during the first half of September and β-pinene thereafter. We observed enhanced MT and monoterpene oxide emissions following the onset of leaf senescence and suggest that senescence has the potential to be a significant control on late-season MT emissions in this ecosystem. We show that common parameterizations of BVOC emissions cannot reproduce the fluxes of MT, C10H16O, and SQT during the onset and continuation of senescence but can correctly simulate isoprene flux. We also describe the impact of the MT emission enhancement on the potential to form highly oxygenated organic molecules (HOMs). The calculated production rates of HOMs and H2SO4, constrained by terpene and DMS concentrations, suggest that biogenic aerosol formation and growth in this region should be dominated by secondary organics rather than sulfate. Further, we show that models using parameterized MT emissions likely underestimate HOM production, and thus aerosol growth and formation, during early autumn in this region. Further measurements of forest–atmosphere BVOC exchange during seasonal transitions as well as measurements of DMS in temperate regions are needed to effectively predict the effects of canopy changes on reactive carbon cycling and aerosol production.

Shade-Induced Leaf Senescence in Plants.

Leaf senescence is a vital developmental process that involves the orderly breakdown of macromolecules to transfer nutrients from mature leaves to emerging and reproductive organs. This process is essential for a plant's overall fitness. Multiple internal and external factors, such as leaf age, plant hormones, stresses, and light environment, regulate the onset and progression of leaf senescence. When plants grow close to each other or are shaded, it results in significant alterations in light quantity and quality, such as a decrease in photosynthetically active radiation (PAR), a drop in red/far-red light ratios, and a reduction in blue light fluence rate, which triggers premature leaf senescence. Recently, studies have identified various components involved in light, phytohormone, and other signaling pathways that regulate the leaf senescence process in response to shade. This review summarizes the current knowledge on the molecular mechanisms that control leaf senescence induced by shade.

Effect of climate warming on the timing of autumn leaf senescence reverses after the summer solstice

Effect of climate warming on the timing of autumn leaf senescence reverses after the summer solstice

Effect of climate warming on the timing of autumn leaf senescence reverses after the summer solstice

Effect of climate warming on the timing of autumn leaf senescence reverses after the summer solstice

Influencia de los intervalos de corte en la calidad del heno de Panicum maximum cv. BRS Tamani en el Cerrado brasileño

The grass Panicum maximum cv. BRS Tamani is a hybrid high-quality, small-sized forage plant with intense tillering activity. This study was carried out to examine the potential of the grass Panicum maximum cv. BRS Tamani at different regrowth ages (49, 63, 77, and 91 d) for hay production, in the rainy period. The experiment was conducted at the Farm School of the Federal University of Mato Grosso do Sul-Brazil, between October 2015 and April 2016. The treatments corresponded to four regrowth ages, with four replicates, distributed into 9 m2 plots. Regrowth ages influenced the morphogenetic characteristics of the grass, except for leaf senescence and final leaf length. Green (9.6–17.6 t ha-1) and dry-matter (2.6–5.9 t ha-1) yields, hay yield (3.4-6.9 t ha-1), and proportions of stem (91.6–455.9 g kg-1) and senescent material (34.8–98.4 g kg-1) increased with the regrowth ages, while the proportion of leaves (837.7-402.1 g kg-1) and the leaf: stem ratio (15.9–0.9) decreased (P<0.05). The dry matter (881.7–852.8 g kg-1) and protein contents (81.2–47.6 g kg-1) of the hay decreased with the higher regrowth ages; however, the neutral detergent fibre (746.5–759.2 g kg-1) acid detergent fibre (519.8–567.7 g kg-1) and lignin (74.3–86.4 g kg-1) contents rose as the regrowth ages did. Nutrient digestibility decreased with the regrowth ages (P<0.05). Panicum maximum cv. BRS Tamani has the potential to produce of hay ha-1, better nutritive value and a high proportion of leaves in the regrowth interval of 49 to 63 d.

Knock out of amino acid transporter gene OsLHT1 accelerates leaf senescence and enhances resistance to rice blast fungus.

Plant amino acid transporters regulate not only long-distance transport and reallocation of nitrogen (N) from source to sink organs, but also the amount of amino acids in leaves hijacked by invading pathogens. However, the function of amino acid transporters in plant defense responses to pathogen infection remains unknown. In this study, we found that the rice amino acid transporter gene OsLHT1 was expressed in leaves and up-regulated by maturation, N starvation, and inoculation of the blast fungus Magnaporthe oryzae. Knock out of OsLHT1 resulted in development stage- and N supply-dependent premature senescence of leaves at the vegetative growth stage. In comparison with the wild type, Oslht1 mutant lines showed sustained rusty red spots on fully mature leaf blades irrespective of N supply levels. Notably, no relationship between the severity of leaf rusty red spots and concentration of total N or amino acids was found in Oslht1 mutants at different developmental stages. Disruption of OsLHT1 altered transport and metabolism of amino acids and biosynthesis of flavones and flavonoids, enhanced expression of jasmonic acid- and salicylic acid-related defense genes, production of jasmonic acid and salicylic acid, and accumulation of reactive oxygen species. OsLHT1 inactivation dramatically prevented the leaf invasion by M. oryzae, a hemi-biotrophic ascomycete fungus. Overall, these results establish a link connecting the activity of an amino acid transporter with leaf metabolism and defense against rice blast fungus.

Effect of climate warming on the timing of autumn leaf senescence reverses after the summer solstice

Effect of climate warming on the timing of autumn leaf senescence reverses after the summer solstice

Physiological and transcriptional responses to heat stress in a typical phenotype of Pinellia ternata.

Pinellia ternata is an important medicinal plant, and its growth and development are easily threatened by high temperature. In this study, comprehensive research on physiological, cytological and transcriptional responses to different levels of heat stress were conducted on a typical phenotype of P. ternata. First, P. ternata exhibited tolerance to the increased temperature, which was supported by normal growing leaves, as well as decreased and sustained photosynthetic parameters. Severe stress aggravated the damages, and P. ternata displayed an obvious leaf senescence phenotype, with significantly increased SOD and POD activities (46% and 213%). In addition, mesophyll cells were seriously damaged, chloroplast thylakoid was fuzzy, grana lamellae and stroma lamellae were obviously broken, and grana thylakoids were stacked, resulting in a dramatically declined photosynthetic rate (74.6%). Moreover, a total of 16 808 genes were significantly differential expressed during this process, most of which were involved in photosynthesis, transmembrane transporter activity and plastid metabolism. The number of differentially expressed transcription factors in MYB and bHLH families was the largest, indicating that these genes might participate in heat stress response in P. ternata. These findings provide insight into the response to high temperature and facilitate the standardized cultivation of P. ternata.

Postharvest illumination of alstroemeria: Effect of light quality on flower metabolism and shelf life

Despite the good postharvest performance of alstroemeria flowers, leaf yellowing is one of the most important signs of senescence and decay, as well as the flower size and time to abscission. In this work, we tested the effect of 50 μmol m−2 s−1 white (WL, broad spectrum) and red-blue (RBL, 40:60, 630 + 465 nm) light-emitting diodes on cut alstroemeria stored at 20 °C, or WL on cut alstroemeria stored at 5 °C, on postharvest flower quality and vase life. The light-treated floral stems had higher water consumption throughout storage compared to the controls stored in the dark, with no variation in stem diameter. The tepal area was increased by the light treatment at both storage temperatures. The leaf color remained similar to that at harvest in the light-treated flower stems (WL and RBL), while there was a strong yellowing in the controls stored in the dark. Anthocyanins increased mostly in flowers stored under WL, although this was more evident at 20 °C. WL treatment strongly slowed chlorophyll degradation and increased sugar content in leaves and tepals by 3.4 and 1.8 times, respectively, at 20 °C, and by 6 and 2.9 times, respectively, at 5 °C. The increase in sugar levels in light-treated flowers may have caused the tepal expansion but also delayed the onset of leaf senescence, and consequently the tepal abscission. The WL was the most effective storage condition not only to extend cut alstroemeria shelf life, but also to improve the postharvest flower quality, both at room temperature and under refrigeration.

Omics-assisted characterization of two-component system genes from Gossypium Raimondii in response to salinity and molecular interaction with abscisic acid.

The two-component system (TCS) genes are involved in a wide range of physiological processes in prokaryotes and eukaryotes. In plants, the TCS elements help in a variety of functions, including cell proliferation, response to abiotic and biotic stresses, leaf senescence, nutritional signaling, and division of chloroplasts. Three different kinds of proteins make up the TCS system in plants. These are known as HKs (histidine kinases), HPs (histidine phosphotransfer), and RRs (response regulators). We investigated the genome of Gossypium raimondii and discovered a total of 59 GrTCS candidates, which include 23 members of the HK family, 8 members of the HP family, and 28 members of the RR family. RR candidates are further classified as type-A (6 members), type-B (11 members), type-C (2 members), and pseudo-RRs (9 members). The GrTCS genes were analyzed in comparison with the TCS components of other plant species such as Arabidopsis thaliana, Cicer arietinum, Sorghum bicolor, Glycine max, and Oryza sativa. This analysis revealed both conservation and changes in their structures. We identified 5 pairs of GrTCS syntenic homologs in the G. raimondii genome. All 59 TCS genes in G. raimondii are located on all thirteen chromosomes. The GrTCS promoter regions have several cis-regulatory elements, which function as switches and respond to a wide variety of abiotic stresses. RNA-seq and real-time qPCR analysis showed that the majority of GrTCS genes are differentially regulated in response to salt and cold stress. 3D structures of GrTCS proteins were predicted to reveal the specific function. GrTCSs were docked with abscisic acid to assess their binding interactions. This research establishes the groundwork for future functional studies of TCS elements in G. raimondii, which will further focus on stress resistance and overall development.

Anatomical, morphogenic and structural characteristics of Xaraés palisade grass under grazing

This study evaluated under grazing intensities and periods of the year: leaf anatomy of Urochloa brizantha cv. Xaraés and its correlation with morphogenetic and structural characteristics, and leaves degradation after in situ incubation. Treatments were four grazing intensities (GI) defined by the pasture residuals leaf area index (rLAI 0.8, 1.3, 1.8, and 2.3) with three replications in a completely randomized design. Cows grazed in a rotational stocking with pastures regrowth period determined by 95% light interception. Leaves showed a higher proportion of sclerenchyma (2.64%) in pastures under lower GI and in the dry season (2.42%). Pastures managed under higher GI showed lower number of expanded leaves (2.58), lower number of lives leaves (3.45), and lower leaf senescence rate (0.05 cm tiller−1 d−1). Positive correlation was observed between leaf elongation rate and adaxial epidermis and vascular tissues. rLAI 1.8 and 2.3 provided greater residues after in situ leaf incubation at times 12, 48, 72, and 96 h compared to rLAI 0.8 and 1.3. rLAI and period of the year had little influence on leaf anatomy of the Xaraés managed under 95% LI, and leaf anatomy is correlated with the morphogenetic and structural pasture characteristics. Pastures managed under lower GI show more residues after leaves incubation in rumen.