Journal of Plant Research最新文献

Salinity and light markedly influence cyanobacterial viability. High salinity disrupts the osmotic balance, while excess light energy affects redox potential in the cells. Regulating the ratio of saturated and unsaturated alka(e)ne and fatty acids in cyanobacteria is thought to have crucial roles in coping with these stresses by regulating membrane fluidity. In Synechococcus elongatus PCC 7942 (Syn7942), alkane is produced from fatty acid metabolites using acyl-acyl carrier protein reductase (Aar) and aldehyde-deformylating oxygenase (Ado) enzymes. However, the role of alka(e)nes and their correlation with fatty acid-related compounds, especially under salinity stress, is not yet fully understood. This study explored the significance of the natural alka(e)ne biosynthesis pathway using Syn7942. The role of alka(e)ne was assessed using single and double knockout mutants of the aar and/or ado genes in this biosynthetic process. The alka(e)ne levels and membrane lipid content exhibited an inverse relationship, correlating with cell fluidity under high-salinity and high-light conditions. The absence of alka(e)ne resulted in a severe growth phenotype of Δado and Δaar/Δado under high-salinity conditions and less severe under high-light conditions. In addition, feeding with C15:0 and/or C17:0 alkanes complemented the growth phenotype with different accumulation profiles. The Δaar mutant exhibited higher resistance to high salinity than the Syn7942 WT, indicating the importance of Ado for survival at high salinity. Overall, lipid-related compounds, especially alka(e)nes, markedly contribute to cell integrity maintenance under high-salinity conditions by regulating membrane rigidity and fluidity.

Breeders adjust wheat heading dates to improve regional adaptability and reduce or mitigate yield losses caused by meteorological disasters, pests and diseases. The Ppd-1 genes play a crucial role in determining wheat sensitivity to changes in day-length and serve as key regulators of heading dates once the vernalization requirement is satisfied. In this study, we identified a new allelic variant of the promoter region, Ppd-B1a.3, in the Chinese wheat cultivar Qingchun 37. Compared to the Ppd-B1b.1 (carried by Chihokukomugi), the main mutation sites in Ppd-B1a.3 include a substitution of C with G at the -505-bp, a T base insertion at the -625-bp, a mutation of TCG to GGT at the -632 to -634-bp, and a 163-bp insertion at the -691 bp. Analysis of F₂ populations indicated that Ppd-B1a.3 promotes heading and flowering (approximately 6 days earlier in population 1 and 17 days in population 2) under short-day conditions in a greenhouse. However, the evaluation of Ppd-B1a.3's effect under field conditions may be influenced by the copy number of the Ppd-B1 locus inherited from the other parent in the F₂ populations. Ppd-B1a.3 disrupts circadian rhythm expression and exhibits a stronger effect on heading and flowering than the three-copy Ppd-B1 allele carried by Jing 411. Origin analysis suggests that Ppd-B1a.3 may have derived from non-native germplasm. These results deepen our understanding of wheat photoperiod genes and provide useful genetic resources for fine-tuning wheat heading dates during breeding.

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.

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.

Thiol/disulfide-based redox regulation is a key mechanism for modulating protein functions in response to changes in cellular redox status. Two thioredoxin (Trx)-like proteins [atypical Cys His-rich Trx (ACHT) and Trx-like2 (TrxL2)] have been identified as crucial for oxidizing and deactivating several chloroplast enzymes during light-to-dark transitions; however, their roles remain to be fully understood. In this study, we investigated the functions of Trx-like proteins in seed development. Using the CRISPR/Cas9 system, we generated an Arabidopsis quadruple mutant defective in ACHT1, ACHT2, TrxL2.1, and TrxL2.2 (acht/trxl2). This mutant showed increased seed lethality prior to maturation, with embryogenesis impaired primarily during the heart and torpedo stages, which are critical phases for plastid differentiation into chloroplasts. Using transgenic plants expressing EGFP-fused proteins, we confirmed that ACHT and TrxL2 are localized in plastids during embryogenesis. Additionally, seed development in the acht/trxl2 mutant was further impaired under extended darkness and could not be recovered through complementation with variants of ACHT or TrxL2 lacking the redox-active Cys residue (replaced by Ser). These findings indicate that the protein-oxidation functions of ACHT and TrxL2 are important for plastid differentiation into chloroplasts, embryogenesis, and seed development.

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.

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.

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.

Cutting-induced adventitious root (AR) formation is crucial for vegetative propagation, a key method that produces plants identical to parent. However, many woody plants pose challenges for vegetative propagation due to difficulties in AR formation. Hormones play important roles during AR formation, with auxin serving as the key regulator and interacting with other hormones. In this review, we summarize the molecular events and hormone functions involved in AR formation in woody plants. A deeper understanding of these processes could enhance the design and manipulation of techniques to improve vegetative propagation in woody plants, ultimately leading to greater economic benefits.

Higher plants are divided into three major photosynthetic groups known as C₃, C₄, and crassulacean acid metabolism (CAM) plants. It is considered that cell wall thickness (T_CW) affects diffusion and leakiness of CO₂ within leaves, but it is unclear whether T_CW of photosynthetic cells differs among these groups. This study investigated T_CW of photosynthetic cells in herbaceous C₃, C₄, and CAM species under an electron microscope. Among 75 species of monocots and eudicots grown in a growth chamber in the same environment, the T_CW of mesophyll cells (MCs) was much higher in CAM species than in C₃ and C₄ species. However, when T_CW was compared between C₃ and C₄ species of grasses and eudicots, T_CW of MCs tended to be lower in C₄ species than in C₃ species; the opposite trend was observed for T_CW of bundle sheath cells (BSCs). T_CW of MCs and BSCs almost did not differ among the C₄ decarboxylation types (NADP-ME, NAD-ME, and PCK). In plants grown outdoors (51 species), similar trends of T_CW were also found among photosynthetic groups, but their T_CW was generally higher than that of growth-chamber plants. This study provides the T_CW spectrum of photosynthetic cells in herbaceous C₃, C₄, and CAM species. The results obtained would be valuable for our understanding of the diffusion and leakage of CO₂ in the leaves of different photosynthetic groups.