Journal of Plant Research最新文献

Sasa senanensis (a dwarf bamboo), an evergreen herbaceous plant native to the cool temperate regions of eastern Asia, endures seasonal temperature fluctuations and significant variations in light intensity typical for understory plants. Following snowmelt in early spring, the light intensity received by Sasa leaves surges, then diminishes as the canopy of upper deciduous trees develops. The current-year leaves of S. senanensis unfold under these shaded conditions, rendering the preservation of overwintering leaves vital for maintaining photosynthetic productivity in early spring. This study investigated the adaptations of overwintering leaves of S. senanensis to the low temperatures and elevated light conditions typical of early spring, examining whether these leaves dissipate absorbed light energy as heat and/or reduce their antenna size in response to increased light levels. Comprehensive analyses of Fv/Fm and photosynthetic pigment compositions were conducted throughout the spring to autumn seasons from 2014 to 2017. Our results indicate that Fv/Fm in overwintering leaves was initially low in early spring but increased gradually before the onset of shading, maintaining high levels under shaded conditions across all examined years. The chlorophyll a/b ratio increased post-snowmelt and decreased with intensified shading annually, with the exception of 2015, suggesting that reductions in antenna size are not essential for Fv/Fm recovery. Furthermore, the quantities and de-epoxidation state of xanthophyll cycle pigments increased after snowmelt despite rising temperatures, then decreased with progressive shading each year, indicating that overwintering leaves adapt to early spring conditions by modulating their xanthophyll cycle pigments. This study demonstrates that the overwintering leaves of S. senanensis exhibit a flexible response in photosystem pigments to variations in the light environment.

Crassulacean acid metabolism (CAM), a specialized mode of photosynthetic carbon assimilation characterized by nocturnal fixation of atmospheric CO₂ and vacuolar malic acid storage, is found in a wide variety of vascular plant species, mainly those inhabiting water-limited environments. Identifying and characterizing diverse CAM species enhances our understanding of the physiological, ecological, and evolutionary significance of CAM photosynthesis. In this study, we examined the effect of CO₂ elimination on chlorophyll fluorescence-based photosynthetic parameters in two constitutive CAM Kalanchoe species and six orchids. In CAM-performing Kalanchoe species, the effective quantum yield of photosystem II showed no change in response to CO₂ elimination during the daytime but decreased with CO₂ elimination at dusk. We applied this method to reveal the photosynthetic mode of epiphytic orchids and found that Gastrochilus japonicus, Oberonia japonica, and Bulbophyllum inconspicuum, but not B. drymoglossum, are constitutive CAM plants, which were also confirmed by malate determination. Our data propose a novel approach to identify and characterize CAM plants without labor-intensive experimental procedures. Although B. drymoglossum leaves had relatively high malate content, they did not depend on it to perform photosynthesis even under water-deficient or increased light conditions. Anatomical comparisons revealed a notable difference in leaf structure between B. drymoglossum and B. inconspicuum; B. drymoglossum leaves possess large water storage tissue internally, unlike B. inconspicuum leaves, which develop pseudobulbs. Our findings suggest different evolutionary adaptations to water deficit between closely related B. drymoglossum and B. inconspicuum.

The oxidative damage induced by abiotic stress factors such as salinity, drought, extreme temperatures, heavy metals, pollution, and high irradiance has been studied in Arabidopsis thaliana. Ultra-weak photon emission (UPE) is presented as a signature reflecting the extent of the oxidation process and/or damage. It can be used to predict the physiological state and general health of plants. This study presents an overview of a potential research platform where the technique can be applied. The results presented can aid in providing invaluable information for developing strategies to mitigate abiotic stress in crops by improving plant breeding programs with a focus on enhancing tolerance. This study evaluates the applicability of charged couple device (CCD) imaging in evaluating plant stress and degree of damage and to discuss the advantages and limitations of the claimed non-invasive label-free tool.

A sessile lifestyle compels plants to endure an array of environmental stressors in the location where they grow. To cope with environmental stresses, plants have developed specialized cell wall structures called cuticles at the interface between the plant and the environment. In Arabidopsis thaliana seedlings, cuticles cover and protect aerial organs and young roots. However, the precise assembly of the molecular machinery required for cuticle formation on the surface of distinct organs that exhibit entirely different functions and developmental contexts remains unknown. Here, we demonstrate that a paralogous gene pair, ARABIDOPSIS THALIANA MERISTEM LAYER1 (ATML1) and PROTODERMAL FACTOR2 (PDF2), regulates precise cuticle formation in Arabidopsis thaliana seedlings. We found that the expression of ATML1 and PDF2 spatially overlapped with cuticle deposition in Arabidopsis thaliana seedlings. Furthermore, the loss of ATML1 and PDF2 activity resulted in a significant downregulation of the expression of genes required for cuticle formation and compromised cuticle formation in different organs. Seedlings with impaired activities of ATML1 and PDF2 exhibited higher susceptibility to environmental stress. In particular, PDF2 plays a predominant role in tolerance to environmental stress rather than ATML1 in the roots. Collectively, our study provides new insights into the regulatory mechanisms of cuticle formation and the developmental strategies plants use to protect their bodies from environmental stresses.

Erythrina is a Pantropical bird-pollinated genus of Fabaceae. Thus, its flowers are usually large, showy, red or yellowish, offering nectar as the principal resource. There are two main interaction systems with birds in Erythrina: in one, the inflorescences are erect and the flowers are horizontal, offering no landing platform; in the other, the inflorescences are horizontal and the flower parts are more exposed. Erythrina speciosa is pollinated by hummingbirds and E. poeppigiana is pollinated by passerines. Despite their structural variation, little is known about how species of the same genus diverge ontogenetically to form flowers adapted to pollinators with different beak morphology and feeding behaviors. Therefore, this study aimed to investigate floral development in two species according to their pollination system. Flowers and buds were collected and fixed for analysis using scanning electron microscopy and light microscopy. Some characteristics are common to both species: the formation of a pseudoracemose inflorescence, the unidirectional emergence of floral organs, and the formation of a short staminal sheath involving nine of the ten stamens (diadelphous androecium). Other characteristics, notably those related to the late stages of floral development, gradually diverged. Among them are inflorescence formation pattern; the formation of reduced and free keel petals in E. speciosa, while in E. poeppigiana they are longer and postgenitally united by their lower margins; and the participation of the standard in the floral display. The studied species share several traits common to other Papilionoideae, but some similarities between the species studied may not be phylogenetically related and reveal the potential ontogenetic pathways of functional convergence that flowers have experienced throughout evolution in the genus.

Barley (Hordeum vulgare L.) is an important cereal crop used in animal feed, beer brewing, and food production. Waterlogging stress is one of the prominent abiotic stresses that has a significant impact on the yield and quality of barley. Seed germination plays a critical role in the establishment of seedlings and is significantly impacted by the presence of waterlogging stress. However, there is a limited understanding of the regulatory mechanisms of gene expression and metabolic processes in barley during the germination stage under waterlogging stress. This study aimed to investigate the metabolome and transcriptome responses in germinating barley seeds under waterlogging stress. The findings of the study revealed that waterlogging stress sharply decreased seed germination rate and seedling growth. The tolerant genotype (LLZDM) exhibited higher levels of antioxidase activities and lower malondialdehyde (MDA) content in comparison to the sensitive genotype (NN). In addition, waterlogging induced 86 and 85 differentially expressed metabolites (DEMs) in LLZDM and NN, respectively. Concurrently, transcriptome analysis identified 1776 and 839 differentially expressed genes (DEGs) in LLZDM and NN, respectively. Notably, the expression of genes associated with redox reactions, hormone regulation, and other biological processes were altered in response to waterlogging stress. Furthermore, the integrated transcriptomic and metabolomic analyses revealed that the DEGs and DEMs implicated in mitigating waterlogging stress primarily pertained to the regulation of pyruvate metabolism and flavonoid biosynthesis. Moreover, waterlogging might promote flavonoid biosynthesis by regulating 15 flavonoid-related genes and 10 metabolites. The present research provides deeper insights into the overall understanding of waterlogging-tolerant mechanisms in barley during the germination process.

Pregnane derivatives such as pregnenolone or progesterone and many other metabolites are important in mammals where many of them act as hormones including sexual hormones. Much less is known about the presence and functions of pregnane derivatives in plants. The main objectives of this work were (1) to determine the presence of pregnane derivatives in winter wheat (2) verify if there are changes of concentration of pregnane derivatives during wheat growth/development with special attention to vernalisation process (3) to answer the question of whether selected pregnane derivatives are stimulators of wheat development and whether the potential stimulation of this development is accompanied by the expression of the Vrn1 (Vernalisation1) gene. To the best of our knowledge, this is the first report that demonstrates the presence of pregnenolone and 5α-dihydroprogesterone in the leaves and intact crowns of winter wheat. The levels of some of the pregnane derivatives changed during plant growth/development, it was demonstrated that pregnenolone, pregnanolone and 17α-hydroxypregnenolone stimulated wheat development. The changes in the Vrn1 expression are discussed in light of the stimulation of generative development by the pregnane derivatives.

Calotropis procera (Aiton) W.T. Aiton is a medicinal plant belonging to the family Apocynaceae as a core source of natural cardenolides. Cardiac glycosides (CGs) are steroid derivatives reported to have the ability to regulate cancer cell survival and death through multiple signaling pathways. Earlier stage-specific and wound-responsive accumulation of CGs and their genin units have already been reported. Recent cumulative evidences have implicated stress and defense response signaling in the production of secondary metabolite in plants. In this report, seasonal accumulation of CGs and its genin units have been explored along with their profiling under control vs stress conditions with a significant accumulation using LC-MS/MS. The study showed that Calotropis procera plants efficiently accumulate CGs and genin units in both winter and summer beside rainy season, as well as under thermal and salinity stress. Among the three cardenolides, the calotropagenin was accumulated more than coroglaucigenin and uzarigenin whereas CGs like calotropin, frugoside, uscharidin, uscharin, and asclepin were significantly accumulated in response to heat, cold and NaCl. Comparatively for hormonal treatments like methyl jasmonate and salicylic acid, targeted metabsolites showed upto twofold accumulation. Gene expression analysis of CG biosynthetic genes also validated the accumulation pattern of the targeted metabolite. This targeted metabolites accumulation enhances plant tolerance to adverse conditions. Gene expression analysis supports this strategy, emphasizing the plant's effective stress management. These findings significantly contribute to our understanding of how plants adapt to stress through the accumulation of metabolites, thereby enhancing their tolerance to challenging environmental conditions.

Information on the kinetic properties of Rubisco, a key enzyme for photosynthesis, is scarce in land plants that emerged early during the evolutionary process. This study examined the carboxylase activity and abundance of Rubisco in five conifers, two lycopods, and three control C₃ crops. The turnover rates of Rubisco carboxylation (k_cat^c) under saturated-CO₂ conditions in conifers and lycopods were comparable to those in the control C₃ crops. Rubisco carboxylase activity under CO₂-unsaturated conditions (v_cu) was also measured using reaction mixtures saturated with a N₂ gas containing CO₂ and O₂ at present atmospheric levels to predict the Rubisco CO₂ affinity from the percentage of v_cu in k_cat^c. The predicted CO₂ affinity in conifers and lycopods tended to be lower than that in the control C₃ crops. When the control C₃ crops and two previously examined C₄ crops were analyzed together, the k_cat^c of Rubisco with a low CO₂ affinity tended to be high. N allocation to Rubisco with a low k_cat^c tended to be high in these plants. In conifers and lycopods, the k_cat^c was lower than that expected on the basis of predicted Rubisco CO₂ affinity, unlike in the control crops. N allocation to Rubisco also tended to be lower than that expected on the basis of k_cat^c. These results indicate that Rubisco in the examined conifers and lycopods is not superior in terms of both k_cat^c and CO₂ affinity and that the abundance of Rubisco is not necessarily closely related to its kinetic properties. The reason for these phenomena is discussed in terms of the molecular evolution of Rubisco.

Since photosynthesis is highly sensitive to salinity stress, remote sensing of photosynthetic status is useful for detecting salinity stress during the selection and breeding of salinity-tolerant plants. To do so, photochemical reflectance index (PRI) is a potential measure to detect conversion of the xanthophyll cycle in photosystem II. Raphanus sativus var. raphanistroides is a wild radish species closely related to domesticated radish, and is distributed throughout the coastal regions of Japan, where it is thought to be salt tolerant. In this study, we raised wild and domesticated radishes under various salt conditions and assessed growth, photosynthetic status, and PRI. When grown at mild salt stress (50 mM NaCl), wild radish leaves showed photosynthetic activity levels comparable to control plants, whereas the photosynthetic activity of domesticated radish was suppressed. This result suggests that wild radishes are more salt-tolerant than domesticated radishes. Although photosynthetic rate and the photochemical quantum yield were significantly correlated with PRI in both species, the PRI resolution was insufficient to distinguish differences in salt tolerance between wild and domesticated radish. Wild radish had a lower maximum quantum yield (Fv/Fm) when grown under moderate salt stress (200 mM NaCl), suggesting chronic photoinhibition. The relationship between non-photochemical quenching (NPQ) and PRI was significant when leaves with chronic photoinhibition were eliminated but this relationship was not significant when they were included. In contrast, the relationship between photosynthesis and PRI was significant regardless of whether leaves displayed chronic photoinhibition or not. We conclude that PRI is useful to detect relatively large reductions in photosynthetic rate under salinity stress, and that care should be taken to evaluate NPQ from PRI.