Transcription factors dealing with Iron-deficiency stress in plants: focus on the bHLH transcription factor family

Integrated transcriptomics and metabolomics elucidate how arbuscular mycorrhizal fungi alleviate drought stress in Juglans sigillata

Walnut (Juglans sigillata), an economically significant ecotype of the Juglans genus in the Juglandaceae family, is cultivated mainly in southwest China, a region prone to seasonal drought. Drought significantly reduced both the yield and quality of walnuts in this area. Arbuscular mycorrhizal fungi (AMF) are symbiotic fungi that colonize plant roots and play crucial roles in enhancing plant drought resistance. This study investigated the effects of AMF on the alleviation of drought stress. Compared to non-inoculated drought-stressed plants, AMF inoculation improved plant growth, increased photosynthetic capacity, enhanced reactive oxygen species (ROS) scavenging ability, and significantly activities of superoxide Dismutase, peroxidase, and catalase were significantly increased by 19.90 %, 18.43 %, and 8.39 %, respectively. malondialdehyde, Superoxide anion, and Hydrogen peroxide levels decreased by 18.39 %, 20.75 %, and 21.44 %, respectively, and soluble sugar and proline concentrations also significantly increased (P < 0.05), helping to maintain the osmotic balance. In addition, transcriptome results showed that ATP-binding cassette transporter related to drought resistance were significantly enriched in plants inoculated with AMF, and genes related to growth, such as IAA and CKT synthesis, transcription factors (BZIP, WRKY, and GTE), and related antioxidant enzymes. The mitogen-activated protein kinases pathway-related genes were upregulated in the inoculated drought treatment group, whereas pinobanksin and homoeriodictyol were upregulated in the inoculated drought treatment group, both of which provide support for drought resistance. In summary, AMF alleviated drought stress and promoted Juglans sigillata growth by modulating key physiological, biochemical, and molecular mechanisms involved in drought resistance. This study offers important theoretical insights that support the application of AMF in sustainable agricultural practices.

Genome-Wide Identification and Cold Stress Response Mechanism of Barley Di19 Gene Family

The Di19 (Drought-induced 19) gene family encodes Cys2/His2-type zinc finger proteins that are known to be involved in plant responses to various abiotic stresses, including drought, salinity, and temperature extremes. However, little is known about their roles in barley (Hordeum vulgare), particularly in cold stress adaptation. This study aimed to conduct a comprehensive genome-wide analysis of the barley genome to identify Di19 gene family members and examine their expression patterns under cold stress, providing theoretical support for stress-resistant barley breeding. By aligning Di19 gene sequences from Arabidopsis and rice and using BLASTp, seven HvDi19 genes were identified in barley. Bioinformatics analysis revealed that all members contain a conserved Cys2/His2-type zinc finger domain and nuclear localization signals. Phylogenetic analysis grouped the HvDi19 genes into four subfamilies, with three homologous gene pairs, and Ka/Ks analysis indicated strong purifying selection. Tissue-specific expression analysis showed significant variation in HvDi19 expression across barley organs. Under cold stress, different barley varieties exhibited distinct HvDi19 gene expression profiles: for instance, HvDi19-1 was downregulated in cold-tolerant varieties, whereas HvDi19-7 showed increased expression in a cold-tolerant mutant, suggesting their potential roles in modulating cold response. These findings reveal the evolutionary conservation and cold-responsive expression characteristics of the HvDi19 gene family, laying a foundation for future functional studies. The results also provide important molecular resources for the genetic improvement of cold tolerance in barley, contributing to the development of stress-resilient crop varieties under climate change.

BAR11, a Ferritin Protein From Saccharothrix yanglingensis Enhances Disease Resistance in Malus domestica by Disrupting Iron Homoeostasis

Previously, we identified BAR11, an uncharacterized protein from the biocontrol actinomycete Saccharothrix yanglingensis Hhs.015, as an elicitor of plant immunity. BAR11 pretreatment significantly suppressed Valsa mali infection in apple (Malus domestica); however, its molecular function remained unclear, as did the mechanisms governing the response of the apples to BAR11 treatment. Here, we demonstrate that BAR11 functions as a ferritin, defined by a conserved four-helical bundle structure, and enhances oxidative stress tolerance in actinomycetes. Confocal microscopy revealed that BAR11 was secreted and delivered into apple cells, where it sequestered labile ferrous iron (Fe2+) and inhibited iron uptake. Notably, BAR11 treatment and iron deficiency induced nearly identical transcriptional reprogramming of iron homoeostasis-related genes in apple roots and similar resistance phenotypes, suggesting that BAR11 triggers a low iron-mimicry state, which potentiates apple immunity. Transcriptomic analysis further supported that BAR11 disrupted the expression of iron homoeostasis-related genes while activating that of defence-related ones. Moreover, the apple WRKY family transcription factor MdWRKY40 responded robustly to BAR11 and low-iron treatments and positively modulated BAR11-induced resistance against V. mali. Our findings reveal a paradigm wherein actinomycete ferritins act as cross-kingdom immune elicitors by disrupting iron homoeostasis in apple, providing a mechanistic foundation for iron-targeted biocontrol strategies.

Starvation from within: How heavy metals compete with essential nutrients, disrupt metabolism, and impair plant growth

Nutrient starvation is a critical consequence of heavy metal toxicity, severely impacting plant health and productivity. This issue arises from various sources, including industrial activities, mining, agricultural practices, and natural processes, leading to the accumulation of metals such as aluminum (Al), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and nickel (Ni) in soil and water. Heavy metal exposure disrupts key physiological processes, particularly nutrient uptake and transport, resulting in nutrient imbalances within the plant. Essential nutrients are often unavailable or improperly absorbed due to metal chelation and interference with transporter functions, exacerbating nutrient deficiencies. This nutrient starvation, coupled with oxidative stress induced by heavy metals, manifests in impaired photosynthesis, stunted growth, and reduced crop yields. This review presents important insights into the molecular mechanisms driving nutrient deprivation in plants exposed to heavy metals, emphasizing the roles of transporters, transcription factors, and signaling pathways. It also examines the physiological and biochemical effects, such as chlorosis, necrosis, and altered metabolic activities. Lastly, we explore strategies to mitigate heavy metal-induced nutrient starvation, including phytoremediation, soil amendments, genetic approaches, and microbial interventions, offering insights for enhancing plant resilience in contaminated soils.

GH3 Gene Family Identification in Chinese White Pear (Pyrus bretschneideri) and the Functional Analysis of PbrGH3.5 in Fe Deficiency Responses in Tomato

Iron (Fe) deficiency poses a major threat to pear (Pyrus spp.) fruit yield and quality. The Gretchen Hagen 3 (GH3) plays a vital part in plant stress responses. However, the GH3 gene family is yet to be characterized, and little focus has been given to the function of the GH3 gene in Fe deficiency responses. Here, we identified 15 GH3 proteins from the proteome of Chinese white pear (Pyrus bretschneideri) and analyzed their features using bioinformatics approaches. Structure domain and motif analyses showed that these PbrGH3s were relatively conserved, and phylogenetic investigation displayed that they were clustered into two groups (GH3 I and GH3 II). Meanwhile, cis-acting regulatory element searches of the corresponding promoters revealed that these PbrGH3s might be involved in ABA- and drought-mediated responses. Moreover, the analysis of gene expression patterns exhibited that most of the PbrGH3s were highly expressed in the calyxes, ovaries, and stems of pear plants, and some genes were significantly differentially expressed in normal and Fe-deficient pear leaves, especially for PbrGH3.5. Subsequently, the sequence of PbrGH3.5 was isolated from the pear, and the transgenic tomato plants with PbrGH3.5 overexpression (OE) were generated to investigate its role in Fe deficiency responses. It was found that the OE plants were more sensitive to Fe deficiency stress. Compared with wild-type (WT) plants, the rhizosphere acidification and ferric reductase activities were markedly weakened, and the capacity to scavenge reactive oxygen species was prominently impaired in OE plants under Fe starvation conditions. Moreover, the expressions of Fe-acquisition-associated genes, such as SlAHA4, SlFRO1, SlIRT1, and SlFER, were all greatly repressed in OE leaves under Fe depravation stress, and the free IAA level was dramatically reduced, while the conjugated IAA contents were notably escalated. Combined, our findings suggest that pear PbrGH3.5 negatively regulates Fe deficiency responses in tomato plants, and might help enrich the molecular basis of Fe deficiency responses in woody plants.

Genome-Wide Identification of GRAS Gene Family in Cunninghamia lanceolata and Expression Pattern Analysis of ClDELLA Protein Under Abiotic Stresses

The Chinese fir (Cunninghamia lanceolata) is a significant species utilized in afforestation efforts in southern China. It is distinguished by its rapid growth and adaptability to diverse environmental conditions. The GRAS gene family comprises a group of plant-specific transcription factors that play a pivotal role in plant growth and development, response to adversity, and hormone regulatory networks. However, the exploration of the GRAS family in gymnosperm Chinese fir has not yet begun. In this study, a total of 43 GRAS genes were identified in the whole genome of Chinese fir, and a phylogenetic analysis classified them into nine distinct subfamilies. Gene structure analysis revealed that the majority of ClGRAS genes lacked introns. It is notable that among these proteins, both ClGAI and ClGRA possess distinctive DELLA structural domains. Cis-acting element analysis revealed that nearly all ClGRAS genes contained light-responsive elements, while hormone-responsive elements, environmental-responsive elements (low-temperature- or defense-responsive elements), and meristem-organization-related elements were also identified. Based on transcriptome data and RT-qPCR expression patterns, we analyzed the expression of ClGAI and ClRGA genes across different developmental stages, hormones, and three abiotic stresses. Subcellular localization analysis demonstrated that ClGAI and ClRGA were localized to the nucleus. Transcriptional activation assays showed that both genes have self-activating activity. In conclusion, the results of this study indicate that the ClGRAS gene family is involved in the response of Chinese fir to environmental stress. Further research on the ClDELLA genes provides valuable information for exploring the potential regulatory network of DELLA proteins in Chinese fir.

Fabrication of Novel Porous Nano-pesticides by Modifying MPN onto Cu-TCPP MOFs to Enhance Bactericidal Efficacy and Modulate Its Bioavailability

Nano-pesticides have attracted much attention in the field of agriculture, due to existing problems such as decreased bactericidal effect and poor adhesion. An environmentally friendly metal porphyrin (Cu-TCPP)-based nanocarrier pesticide release of diniconazole (DIN) was designed to enhance bactericidal efficacy and modulate its bioavailability in a multidimensional manner by constructing a metal phenolic network (MPN) encapsulation. The introduction of the MPN prevents the DIN from prematurely escaping from the Cu-TCPP@DIN@MPN in the environment and gives it strong interfacial adhesion to resist rain washing. The resulting Cu-TCPP@DIN@MPN nanoparticles (NPs) showed a lamellar stacked embedded structure, which improved the inhibition of Fusarium oxysporum (90.9%) and photostability (67.2%), while they do not affect healthy plant growth and meet the relevant food safety requirements for DIN residues. This work provides new ideas for the development of superior photostable, adhesive, rainwater erosion-resistant, and sustainable nanocarrier pesticides.