Plant Physiology and Biochemistry最新文献

Soil salinization is a major environmental factor that severely affects global agriculture. Root endophytes can enter root cells, and offer various ecological benefits, such as promoting plant growth, improving soil conditions, and enhancing plant resistance. Su100 is a novel strain of endophytic fungus that was characterized from blueberry roots. In this study, we focused on evaluating the effects of Su100 secretion on maize growth. The results demonstrated that maize treated with Su100 fermentation broth (SFB) exhibited significantly stronger salt tolerance than the control. It is worth mentioning that the treated root system not only had an advantage in terms of biomass but also a change in root structure with a significant increase in lateral roots (LRs) compared to the control. Transcriptome analysis combined with hormone content measurements indicated that SFB upregulated the auxin signaling pathway, and also caused alterations in brassinosteroids (BR) and jasmonic acid (JA) biosynthesis and signaling pathways. Transcriptome analyses also indicated that SFB caused significant changes in the sugar metabolism of maize roots. The major changes included: enhancing the conversion and utilization of sucrose in roots; increasing carbon flow to uridine diphosphate glucose (UDPG), which acted as a precursor for producing more cell wall polysaccharides, mainly pectin and lignin; accelerating the tricarboxylic acid cycle, which were further supported by sugar content determinations. Taken together, our results indicated that the enhanced salt tolerance of maize treated with SFB was due to the modulation of sugar metabolism and phytohormone biosynthesis or signaling pathways. This study provided new insights into the mechanisms of action of endophytic fungi and highlighted the potential application of fungal preparations in agriculture.

Photosynthesis in fluctuating light requires coordinated adjustments of diffusion conductance and biochemical capacity, but the role of chloroplast ATP synthase activity (g_H⁺) in dynamic photosynthesis is not well understood. In this study, we measured gas exchange, chlorophyll fluorescence and electrochromic shift signals in fluctuating light for leaves of tomato (Solanum lycopersicum) and maize (Zea mays). During the transition from sun to shade, simultaneous increases in g_H⁺, effective quantum yield of PSII, and net CO₂ assimilation rate (A_N) occurred in tomato but uncoupled in maize, indicating that g_H ⁺ limited A_N during the sun-to-shade transition in tomato but not in maize. During the shade-to-sun transition, g_H ⁺ increased simultaneously with stomatal conductance, mesophyll conductance and Rubisco carboxylation capacity in tomato, suggesting that g_H⁺ is an overlooked factor affecting light induction of A_N in tomato. By comparison, g_H ⁺ maintained at high levels in maize and its A_N was mainly restricted by stomatal conductance. Our results reveal that the kinetics of g_H⁺ in fluctuating light differs between species, and chloroplast ATP synthase may be a potential target for improving dynamic photosynthesis in crops such as tomato.

In recent years, the widespread application of growth regulators and nutrients to boost yield and quality of strawberry fruits has led to the rapid growth of strawberry industry globally. Although the effects of major nutrients on strawberry yield have been widely studied, investigations into the effect of trace elements such as boron remain limited. This study examined the effect of boron application on the yield and quality of “Benihoppe” strawberry fruits. Nutrient solutions with varying boron concentrations (0, 0.024, 0.048, 0.072, and 0.096 mM) were applied to the plants, and their effect on fruit quality was evaluated. The results indicated that boron application enhanced the yield per plant, nutrient composition (total amino acid and vitamin C content), antioxidant properties (total phenol) and volatile components (esters) in strawberry fruits. Specifically, treatment with 0.048 mM boron concentration significantly increased the accumulation of soluble sugars, such as sucrose, whose concentration was 154.29% higher than that of the control treated with 0 mM concentration. This enhancement is attributable to the regulated expression of sucrose phosphate synthase (maker-Fvb2-2-augustus-gene-229.38) and β-fructofuranosidase-1/2/3 (augustus-masked-Fvb5-4-processed-gene-2.0, maker-Fvb5-3-augustus-gene-272.30, and maker-Fvb5-1-augustus-gene-0.37) genes, which play crucial roles in sugar metabolism and enzyme activity. Overall, boron application enhanced the quality of “Benihoppe” strawberries. The findings of this study offer substantial theoretical and practical guidance for using boron fertilizers in strawberry farming.

The transcription factor Ethylene Responsive Factor (ERF) is crucial for responding to various environmental stressors. Proteins containing the ERF-associated amphiphilic repression (EAR) motif often inhibit gene expression. However, the functions of LkERF, an EAR motif-containing protein from Larix kaempferi, especially in reactive oxygen species (ROS) homeostasis, are not well understood. In the present research, we introduce a novel transcription factor, LkERF6, which contains an EAR motif and positively regulates gene expression, thereby enhancing drought and salt tolerance in tobacco. LkERF6 is classified within the ERF-B1 subfamily due to its conserved AP2/ERF domain and EAR motif. Subcellular localization assays demonstrated LkERF6 is primarily localized in the nucleus. Further analysis revealed that LkERF6 interacts with GCC and DRE elements and is significantly induced by NaCl and PEG₆₀₀₀. Moreover, LkERF6 transgenic tobacco plants exhibit lower ROS accumulation and higher levels of antioxidant enzyme activities. Additionally, correlation analysis identified a strong association between LkERF6 and three genes: LkSOD, LkCCS, and LkCAT. Y1H, EMAS, and DLR assays confirmed that LkERF6 directly interacts with the promoters of these genes through GCC-box and DRE-box to activate their expression. These findings shed new light on the function of EAR motif-containing transcription factors and highlight LkERF6's crucial role in enhancing abiotic stress resistance by activating multiple ROS clearance genes.

This study elucidates the impact of element dose during nanoparticle (NPs) synthesis on plant growth indices. Novel NPs containing two essential micro-nutrients, zinc (Zn) and manganese (Mn), were co-doped on cerium oxide (CeO₂) (ZnMnCe) with different ratios (1, 2, and 3%). The synthesized NPs were characterized by advanced analytical techniques (EDX, TEM, SEM, XPS, and XRD) and hydroponically applied to barley (Hordeum vulgare L.). The impact of ZnMnCe NPs on growth indices and plant nutrients was examined. SEM, HRTEM, and confocal microscopy were used to show the morphological and structural influences of ZnMnCe NPs. Results showed that the plant growth indices (root/leaf length, chlorophyll fluorescence, pigmentation, and biomass) were remarkably improved with a 1% Mn/Zn addition. Conversely, growth retardation, cell membrane damage, root morphology deformation, and genotoxicity were apparent by 3% of Mn/Zn addition. Overall, a significant improvement in growth was revealed when Mn and Zn were included at 1%. However, increasing concentrations (2% and 3%) impaired the growth. These results show that the element ratio used in NPs synthesis is essential in the plant's physiological response. Precise adjustment of element dosage during NPs synthesis determines whether the NPs are beneficial or harmful. This must be well-balanced for nanofertilizer production and plant applications.

Lipids and Ca²⁺ are involved as intermediate messengers in temperature-sensing signaling pathways. Arbuscular mycorrhizal (AM) symbiosis is a mutualistic symbiosis between fungi and terrestrial plants that helps host plants cope with adverse environmental conditions. Nonetheless, the regulatory mechanisms of lipid- and Ca²⁺-mediated signaling pathways in mycorrhizal plants under cold and heat stress have not been determined. The present work focused on investigating the lipid- and Ca²⁺-mediated signaling pathways in arbuscular mycorrhizal (AM) and non-mycorrhizal (NM) roots under temperature stress and determining the role of Ca²⁺ levels in AM symbiosis and temperature stress tolerance in perennial ryegrass (Lolium perenne L.) Compared with NM plants, AM symbiosis increased phosphatidic acid (PA) and Ca²⁺ signaling in the roots of perennial ryegrass, increasing the expression of genes associated with low temperature (LT) stress, including LpICE1, LpCBF3, LpCOR27, LpCOR47, LpIRI, and LpAFP, and high temperature (HT) stress, including LpHSFC1b, LpHSFC2b, LpsHSP17.8, LpHSP22, LpHSP70, and LpHSP90, under LT and HT conditions. These effects result in modulated antioxidant enzyme activities, reduced lipid peroxidation, and suppressed growth inhibition caused by LT and HT stresses. Furthermore, exogenous Ca²⁺ application enhanced AM symbiosis, leading to the upregulation of Ca²⁺ signaling pathway genes in roots and ultimately promoting the growth of perennial ryegrass under LT and HT stresses. These findings shed light on lipid and Ca²⁺ signal transduction in AM-associated plants under LT and HT stresses, emphasizing that Ca²⁺ enhances cold and heat tolerance in mycorrhizal plants.

Cadmium (Cd) is a significant heavy metal contaminant within the environment, carrying a notable level of toxicity that presents a substantial hazard to both plant and human. Carrot (Daucus carota), a significant root vegetable crop globally, have evolved multiple transcriptional regulatory mechanisms to cope with Cd stress, with a crucial involvement of the myeloblastosis (MYB) transcription factor. In this study, the DcMYB62 gene encoding 288 amino acids, localized in the nucleus and demonstrated transcription activation property, was isolated from carrot (cv. ‘Kuroda’). There was a positive relationship observed between the levels of DcMYB62 expression and the accumulation patterns of carotenoids in two distinct carrot cultivars. Further investigation revealed that the expression of DcMYB62 improved Cd tolerance of Arabidopsis by increasing seed germination rate, root length, and overall survival rate. The levels of carotenoids in DcMYB62 transgenic Arabidopsis surpassed those in wild type, accompanied by elevated expression levels of 15-cis-phytoene desaturase, zeta-carotene desaturase, and carotenoid isomerase. Meanwhile, the heterologous expression of DcMYB62 promoted the biosynthesis of abscisic acid (ABA) and hydrogen sulfide (H₂S), which in turn suppressed the formation of hydrogen peroxide and superoxide anion, while also stimulating stomatal closure. Furthermore, the heterologous expression of DcMYB62 increased the transcription of genes associated with heavy metal resistance in Arabidopsis, notably nicotianamine synthase. Overall, this study contributes to understanding how DcMYB62 promote Cd stress resistance of plants by regulating the biosynthesis pathways of carotenoids, ABA, and H₂S, which offers valuable insights into the regulatory mechanism connecting DcMYBs with Cd stress response of carrot.

APETALA2/ethylene-responsive (AP2/ERF) plays crucial roles in resisting diverse stresses and in regulating plant growth and development. However, little is known regarding the structure and function of the AP2/ERF genes in pearl millet (Pennisetum glaucum). The AP2/ERF gene family may be involved in the development and maintenance of P. glaucum resilience to abiotic stresses, central to its role as a vital forage and cereal crop. In this study, PgAP2/ERF family members were identified and comprehensive bioinformatics analyses were performed, including determination of phylogenetic relationships, gene structures, conserved motifs, chromosomal localization, gene duplication, expression pattern, protein interaction network, and functional characterization of PgRAV_01 (Related to ABI3/VP1). In total, 78 PgAP2/ERF members were identified in the P. glaucum genome and classified into five subfamilies: AP2, ERF, DREB, RAV, and soloist. Members within the same clade of the PgAP2/ERF family showed similar gene structures and motif compositions. Six duplication events were identified in the PgAP2/ERF family; calculation of Ka/Ks values showed that purification selection dominated the evolution of PgAP2/ERFs. Subsequently, a potential interaction network of PgAP2/ERFs was generated to predict the interaction relationships. Additionally, abiotic stress expression analysis showed that most PgAP2/ERFs were induced in response to drought and heat stresses. Furthermore, overexpression of PgRAV_01 negatively regulated drought tolerance in Nicotiana benthamiana by reducing its antioxidant capacity and osmotic adjustment. Taken together, these results provide valuable insights into the characteristics and functions of PgAP2/ERF genes, with implications for abiotic stress tolerance, and will ultimately contribute to the genetic improvement of cereal crop breeding.

Nanomaterials as an emerging tool are being used to improve plant's net photosynthetic rate (A_N) when suffering salt stress, but the underlying mechanisms remain unclear. To clarify this, a hydroponic experiment was conducted to study the effects of polyacrylic acid coated nanoceria (PNC) on the A_N of salt-stressed cotton and related intrinsic mechanisms. Results showed that the PNC-induced A_N enhancement of salt-stressed leaves was strongly facilitated by the mesophyll conductance to CO₂ (g_m). Further analysis showed that the PNC-induced improvement of g_m was related to the increased chloroplast surface area exposed to intercellular airspaces, which was attribute to the increased mesophyll surface area exposed to intercellular airspaces and chloroplast number due to the increased K⁺ content and decreased reactive oxygen species level in salt-stressed leaves. Interestingly, our results also showed that PNC-induced variations in cell wall composition of salt-stressed cotton leaves strongly influenced g_m, especially, hemicellulose and pectin. Moreover, the proportion of pectin in cell wall composition played a more important role in determining g_m. Our study demonstrated for the first time that nanoceria, through alterations to anatomical traits and cell wall composition, drove g_m enhancement, which ultimately increased A_N of salt-stressed leaves.

Waterlogging stress is a severe abiotic challenge that impedes plant growth and development. Ramie (Boehmeria nivea L.) is a Chinese traditional characteristic economic crop, valued for its fibers and by-products. To investigate the waterlogging tolerance of ramie and provide the scientific basis for selecting waterlogging-tolerant ramie varieties, this study examined the morphological, physiological, biochemical, and molecular responses of 15 ramie germplasms (varieties) under waterlogging stress. The results revealed varied impacts of waterlogging stress across the 15 ramie varieties, characterized by a decrease in SPAD values, net photosynthesis rates, and relative water content of ramie leaves, along with a significant increase in relative conductivity and the activities of antioxidant enzymes such as SOD, POD, CAT, and APX. Additionally, the levels of soluble sugars, soluble proteins, and free proline exhibited varying degrees of increase. Through Principal Component Analysis (PCA), ZZ_2 and ZSZ_1 were identified as relatively tolerant and susceptible varieties. Transcriptome analysis showed that the differential expressed genes between ZZ_2 and ZSZ_1 were significantly enriched in metabolic pathways, ascorbate and aldarate metabolism, and inositol phosphate metabolism, under waterlogging stress. In addition, the expression of hypoxia-responsive genes was higher in ZZ_2 than in ZSZ_1 under waterlogging stress. These differences might account for the varied waterlogging responses between the two varieties. Therefore, this study explored the morpho-physiological responses of ramie under waterlogging stress and identified the molecular mechanisms involved, providing valuable insights for improving ramie varieties and breeding new ones.