Journal of Plant Research最新文献

Trichoderma spp., as excellent biocontrol agents, can induce systemic resistance to protect plants from phytopathogen attacks. In a previous study, Trichoderma biofertilizer activated the MsERF105 transcription factor (TF), which further enhanced the resistance of Malus sieversii against Alternaria alternata f. sp. mali, but how resistance signals are transmitted is still unknown. In this study, it was found that the MsERF105-centered disease-resistant regulatory network was induced by Trichoderma in M. sieversii. The TF-centered yeast one-hybrid indicated that WRKY33 and WRKY40 bound to WBOXATNPR1 elements and GT1 bound to GT1CONSENSUS elements in the promoter of MsERF105 to activate its expression. In addition, the proteins that interacted with MsERF105 were identified by yeast two-hybrid, including FUBP2 and HSP17.8. Furthermore, the candidate target genes of MsERF105 were screened using RNA-Seq, and yeast one-hybrid and tobacco transient transformation further showed MsERF105 bound to GCCBOX elements to regulate the expression of bHLH162, ERF017, NAC83 and NAC104; bound to CCAATBOX elements to regulate the expression of HSFs, HSP70s and HSP20; and bound to ERS elements to regulate the expression of DRPs. Finally, the Trichoderma-induced MsERF105-centered regulatory network of M. sieversii against A. alternata f. sp. mali was built, which provided reliable theoretical guidance for the application of Trichoderma and the disease-resistance breeding of M. sieversii.

The summer heat is a vital factor limiting the introduction of relatively large-leaf Rhododendron plants to low-altitude areas, making it crucial to evaluate the resistance of different germplasm to summer heat. A pot experiment was conducted in 2023 to investigate the temporal changes in the photosynthetic characteristics, physiological and biochemical characteristics, and chlorophyll fluorescence characteristics of 14 representative relatively large-leaf Rhododendron germplasm. The results showed the R. irroratum and 'Hotspur Red' exhibited the highest heat damage index (HDI), while R. jiulongshanense and 'Moser Maroon' had the lowest HDI among the 14 Rhododendron germplasm. The photosynthesis rate and F_v/F_m (maximum photochemical efficiency) initially decreased and then recovered in all germplasm except R. irroratum. In contrast, the leaf transpiration rate, stomatal conductance, and chlorophyll content gradually increased. Hydrogen peroxide concentration first decreased and then increased, while malondialdehyde concentration initially increased and then decreased. Additionally, the superoxide anion content gradually increased. The activities of superoxide dismutase, peroxidase, and catalase (CAT) initially increased and then decreased. The HDI was positively correlated with CAT activity (r = 0.28, P < 0.05) but negatively correlated with photosynthesis rate (r = -0.26, P < 0.05), leaf transpiration rate (r = -0.27, P < 0.05), and F_v/F_m (r = -0.43, P < 0.001). Variation in summer heat resistance, as indicated by HDI, was observed among the 14 Rhododendron germplasm. This heat resistance was mainly associated with leaf transpiration rate and F_v/F_m. The indirect role of antioxidant enzymes in maintaining reactive oxygen species homeostasis in summer heat resistance was observed. The results provide a reference for introducing and cultivating relatively large-leaf Rhododendron plants to low-altitude areas.

The physical filtering of pollinators is an important factor influencing pollination effectiveness. This study explored the potential functions of dense hairs that completely obstruct the entrance of floral tube in Marsdenia tinctoria by characterizing the flowers of this species, as well as its pollinators and their behavior. The corolla was white upon blooming in the morning, then turned yellow at night, and the flower finally dropped by the third morning. The hairs tended to be disheveled in yellow-petaled flowers. Pollination success increased with floral age. Direct observations of flowers in natural M. tinctoria populations over a period of 32 h recorded 126 visitors, of which 70% were wasps. We observed pollinia attached to the mouthparts of wasps, carpenter bees, and honeybees, but not to those of butterflies, moths, flies, or ants. Detailed examination of insect mouthparts and floral morphology indicated that insect visitors that acted as pollinators had mouthparts longer than the floral tubes, equipped with hairs to which pollinia could attach. The mouthparts of potter wasps were often covered with pollinaria, carrying on average 30-75 pollinia. The dense floral hairs were penetrated by large-bodied visitors, and blocked smaller visitors. Disturbance of these floral hairs allowed smaller insects to access nectar, suggesting that the hairs function in preventing nectar theft by smaller insects. This study presents the first case of wasp pollination in the genus Marsdenia and provides insights into the potential function of its dense floral hairs, a synapomorphy of this genus, in filtering floral visitors.

Plants generate electrical signals in response to mild and severe environmental stimuli to transmit physiological information and ultimately trigger defensive responses during stressful events. It has been proposed that detecting and characterizing such signals could allow researchers to mimic specific electrical stimuli and provoke desirable responses in crops. Nevertheless, manually inserting electrodes in plant tissues leads to irregular data records due to a lack of uniformity across insertion events. For this reason, we manufactured a prototype of an electrode/needle insertion device built in aluminum and acrylic and used it to measure electrical signals in C. annuum plants. As a result, the device had more consistent insertion characteristics such as depth and alignment between electrodes and with plant stems. The device was also used to obtain electrical signals and compare them with the signals obtained using the traditional insertion technique, demonstrating that the use of the device promotes stability and repeatability in the captured signals.

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.

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.