Bud dormancy is a key adaptive strategy in perennial plants, enabling them to survive adverse environmental conditions. However, it poses challenges in crop cultivation, especially in fruit crops such as apple, in which synchronized bud break is crucial for consistent growth and yield. The synthetic cytokinin 6-benzylaminopurine (6-BA) promotes dormancy release; however, its molecular and metabolic mechanisms remain largely unclear. This study investigates dormancy release in nursery-grown Xianheng 01 apple rootstocks through integrated transcriptomic, metabolomic, and hormonal analyses. Dormant buds were treated with 6-BA, with morphological, biochemical, and molecular profiling performed over 30 d. 6-BA treatment increased plant height and leaf emergence by increasing the levels of cytokinins (DHZR, IPA) and decreasing the level of abscisic acid (ABA). Transcriptomics analysis identified 7,009 differentially expressed genes (DEGs) in response to 6-BA treatment. The cytokinin-responsive gene A-ARR8 exhibited a distinct expression pattern, being upregulated at 1, 3, and 6 d post-treatment but downregulated at 11 d. In contrast, ABA-related genes SnRK2a/b, PP2C, and ABF3, were consistently downregulated throughout the treatment period. Metabolomic analysis identified 2,053 metabolites, showing early-phase dominance of phenylpropanoids, and flavonoids, followed by a shift towards ABC transporter-mediated nutrient mobilization. Conjoint analysis highlighted the coordinated activation of secondary metabolite biosynthesis and cytokinin signaling. These results demonstrate that 6-BA induces dormancy release through cytokinin–ABA antagonism and phased metabolic reprogramming from stress defense to growth promotion. Our findings provide a comprehensive framework for optimizing dormancy management in apple cultivation and highlight 6-BA as an effective agrochemical for improving temperate fruit production.
Avian pathogenic Escherichia coli (APEC) can cause colibacillosis, which is economically devastating to poultry industries worldwide. The bacterial membrane is critical to its environment adaptability and virulence. The inner membrane protein TolA maintains membrane integrity, but its roles in the fitness and pathogenesis of APEC are not completely understood. Thus, a tolA gene mutant and complemented strains of APEC were constructed and characterized. Mutant strain ΔtolA showed damage in the inner and outer membranes, as well as altered morphology, impaired flagella production, reduced motility, increased outer membrane vesicle (OMV) production, and reduced resistance to antibiotics and environmental stress. Deletion of the tolA gene resulted in significant reductions in biofilm formation and interbacterial competition, due to the downregulated expression of biofilm-associated genes and type VI secretion system (T6SS) genes, respectively. In addition, the mutant strain exhibited reductions in serum bactericidal resistance, cell infection capacity, intracellular survival, consequently leading to attenuated bacterial survival and virulence in mice. Compared with the wild-type and complemented strains, the mutant strain induced less expression of inflammatory cytokine interleukin 1 beta (IL-1β) in HD-11 macrophages, consistent with the pathological damage in mice. In conclusion, inner membrane protein TolA contributes to the antibiotic resistance, environmental adaptability, biofilm formation and virulence of APEC.
Prohexadione-calcium (Pro-Ca) has been shown to positively regulate crop tolerance to saline–alkali stress. However, the optimal concentration of Pro-Ca application and the mechanisms through which it enhances saline–alkali tolerance and yield in soybean remain unclear. This study aimed to determine the optimal concentration of exogenously applied Pro-Ca and reveal the mechanisms underlying Pro-Ca’s effect on remediation and yield response in soybean under saline–alkali stress. The results indicated that saline–alkali stress negatively impacted the morphological and physiological traits of soybean seedlings by triggering the production of reactive oxygen species (ROS), leading to oxidative damage of the grana lamellae due to excessive accumulation of Na+. An application of 100 mg L−1 Pro-Ca was found to be optimal, promoting dry matter accumulation and normalized difference vegetation index (NDVI) by significantly reducing Na+ uptake under saline–alkali stress. Moreover, integrated physiological, ultrastructural, and transcriptomic analyses indicated that Pro-Ca significantly enhanced the ascorbate–glutathione (AsA–GSH) cycle by up-regulating the expression of related genes to enhance the activities of ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), and the AsA/dehydroascorbate (DHA) and GSH/oxidized glutathione (GSSG) ratios to quench ROS, thereby protecting both thylakoid and mitochondrial membranes from degradation. The differentially expressed genes (DEGs) encoding ascorbate and aldarate metabolism were significantly (P<0.05) enriched in the integral component of the membranes. Furthermore, Pro-Ca treatment up-regulated the expression of genes encoding photosystems under saline–alkali stress, thereby reducing the photoinhibition and stomatal limitation (Ls), mitigating damage to photosystems, and preventing yield reduction. In summary, foliar application of Pro-Ca could efficiently enhance soybean seedlings’ tolerance to saline–alkali stress by inhibiting Na+ influx, enhancing the AsA–GSH cycle, maintaining the biomembrane system, and improving photosynthetic efficiency.
Leaf rust is a highly destructive foliar disease in wheat which causes major constraints in wheat production worldwide. In this study, we conducted a comprehensive assessment of adult plant resistance to leaf rust in 590 accessions from the advanced backcross-nested association mapping plus inter-crossed (AB-NAMIC) population. We used 660K genotype data to perform a genome-wide association study (GWAS), which identified significant quantitative trait loci (QTLs) on chromosomes 1B, 2A, 2B, and 7D, and then focused on the candidate gene TaRLK-1B on chromosome 1B. A cleaved amplified polymorphic sequence (CAPS) marker developed based on TaRLK-1B haplotypes could effectively differentiate between resistant and susceptible varieties. This gene encodes a membrane-localized leucine-rich repeat receptor-like kinase (LRR-RLK) that is upregulated in response to the fungal infection that causes leaf rust. Targeted knockout of TaRLK-1B in wheat led to reduced resistance to leaf rust, underscoring its essential role as a positive regulator of the defense against this disease. We propose that TaRLK-1B interacts with the receptor-like cytoplasmic kinase TaRLCK1B, potentially facilitating immune signal transduction. Our findings also demonstrate that pyramiding minor effect QTLs significantly increases resistance to leaf rust. This study provides novel insights into rust resistance genes and valuable QTL information, which can improve marker-assisted wheat breeding efforts.
Soil compaction has become a serious limitation for further increasing the grain yield of maize (Zea mays L.) in the North China Plain (NCP). However, considerable variability exists among maize hybrids in their grain yield responses to soil compaction. To understand the physiological processes related to the variation of responses among maize hybrids to different soil compaction levels, a two-year field experiment was conducted with 17 maize hybrids and three soil compaction treatments (NC, no compaction with soil bulk density (SBD) of 1.0–1.3 g cm–3; MC, moderate compaction with SBD of 1.4–1.5 g cm–3, and HC, heavy compaction with SBD>1.6 g cm–3) to examine the root and shoot morphological traits, dry matter accumulation, and grain yield. Compared to NC, MC and HC significantly reduced the maize yield by 0.9–26.7% and 5.9–41.1% across the hybrids and years, respectively. Hybrids with high compaction tolerance (H) had greater grain yield than those with middle compaction tolerance (M) and low compaction tolerance (L), particularly under HC. The yield benefits obtained from the H hybrid were enhanced due to better root and shoot growth under HC conditions. Greater root length, root surface area, and root weight, as well as root activity, absorption capacity, and antioxidant capacity for H hybrid was found under HC conditions, and it also showed increased leaf area index and dry matter accumulation. Moreover, the increases in root growth indices for the H hybrid were greater than that of shoot growth, particularly under HC conditions, leading to a greater root/shoot ratio. We conclude that soil compaction impacts maize root and shoot growth differently depending on genotype, and the root growth advantages of the H hybrid were more obvious than shoot growth, which enhanced the yield benefits from the H hybrid under heavy compaction conditions.
