Plant Growth Regulation最新文献

Plant growth-promoting rhizobacteria (PGPR) are a crucial component of the soil microbiome. They have attracted noteworthy interest due to their plant growth- and health-enhancing effects. PGPR enhances plant growth through several biochemical pathways, such as phytohormone production, solubilizing plant-inaccessible phosphate, nitrogen fixation, siderophore production, and ACC deaminase activation. Collectively, these biochemical pathways contribute to improved nutrient uptake, plant growth, and stress tolerance, underscoring the importance of PGPR in sustainable agriculture. This review analyzes the existing research on PGPR, highlighting their associated biochemical pathways, molecular interactions, and ecological consequences in agriculture. The significant identified aspects include the synthesis of phytohormones, including cytokinins and auxins; phosphate solubilization; and nitrogen fixation, all essential for plant stress resistance and development. The review highlights the ecological and agricultural implications of PGPR. PGPR reduces reliance on chemical pesticides by naturally suppressing plant pathogens and reduces reliance on chemical fertilizers needed to improve nutrient uptake. The review addresses the potential challenges of complicated biochemical reactions related to PGPR–plant interactions, exploring how these reactions can be optimized for better plant growth and health. The review article discourses the challenges modeled by strain specificity, wide-ranging soil conditions, and potential environmental influences of PGPR. It also discusses the essentials for further research into new PGPR strains, long-term field studies, and biochemical pathways to advance sustainable agronomic practices.

Flooding is a critical environmental challenge that affects plant growth and development, and its frequency and severity are expected to increase with climate change. Plants have evolved diverse acclimation responses to survive under unfavorable conditions. Some plants adopt either escape or quiescence strategies when submerged. In an escape strategy, plants elongate their internodes to maintain essential gas exchange, whereas in a quiescent strategy, they rely on carbohydrate reserves to sustain vital metabolic processes during submergence. Ethylene is a key player in plant adaptation to flooding and modulates signaling and metabolic responses. Although significant progress has been made in unraveling the fundamental physiological and molecular mechanisms associated with ethylene-mediated plant responses to flooding stress, our knowledge in this field is still incomplete. Understanding how plants cope with unforeseen flood events is crucial for developing resilient crop varieties. This review provides recent discoveries and an overview of plant responses and tolerance mechanisms to flooding stress, encompassing cellular signaling and morphological adaptations. By examining these aspects, we aimed to catalyze innovative approaches for crop improvement to enhance flood resilience.

The elongation of the mesocotyl is modulated by phytohormones, which have been shown to exert both synergistic and antagonistic influences on this process. However, the complex regulatory networks involved remain to be fully understood. To investigate the interplay between strigolactone (SL) and brassinosteroid (BR) signaling pathways in the regulation of mesocotyl elongation, we analyzed the elongation phenotypes of mutants deficient in SL and BR signaling. Our findings indicate that the SL signaling pathway operates downstream of the BR signaling pathway during mesocotyl elongation. Furthermore, a comprehensive analysis of genome-wide expression profiles in response to BR treatment demonstrated that BR signaling activation inhibits carotenoid biosynthesis, while the inhibition of SL signaling alters the mesocotyl’s sensitivity to BR. This suggests a potential convergence of SL and BR pathways in regulating shared target genes during mesocotyl development. The results indicate that both SL and BR signaling pathways can influence mesocotyl elongation through the action of BBX6. These findings will enhance our understanding of the underlying mechanisms of mesocotyl development and provide valuable insights for the breeding elite rice varieties suitable for direct seeding.

Barley (Hordeum vulgare L.) is the fourth most productive cereal crop in the world, but barley sown in winter is often infected by the barley yellow mosaic virus (BaYMV) and the barley mild mosaic virus (BaMMV), which cause mosaic, stunting, discoloration and yield reduction. Plant microRNA (miRNA) plays a major part in defense against viral infection. In this study, total sRNAs from the leaves of three barley cultivars infected with a soil-borne virus, BaYMV or BaMMV, were analyzed by RNA sequencing. A total of 35 known miRNAs and 70 novel miRNAs were identified, of which hvu-miR397a and huv-miR156a were most differentially expressed. A total of 18 miRNAs were found to target 259 genes. Enrichment analysis revealed that targeted genes were associated with chloroplast functions. Overall, the results provided a whole landscape of small RNAs and mRNAs in response to BaYMV infection and can be referred to in plant breeding against virus infection.

Eugenol is one of the most important phenylpropanoid volatiles in strawberry fruit. The DOF (DNA binding with One Finger) proteins are plant-specific transcription factors, which are involved in diverse biological processes. However, the molecular mechanism of how the DOF transcription factors regulate eugenol biosynthesis is poorly understood. In this study, the novel DOF transcription factor, Fragaria × ananassa DOF1 (FaDOF1), was identified and characterized. Analysis of subcellular localization using GFP showed that FaDOF1 was localized in the nucleus. FaDOF1 was highly expressed in flowers and peaked at small green fruit stage during maturity. Eugenol concentrations at different developmental stages and tissues had significant correlations with the transcription levels of FaDOF1. Transient overexpression and silencing of FaDOF1 promoted and repressed eugenol accumulation in strawberry fruit, respectively. Y1H, GUS, and dual-LUC assays indicated that FaDOF1 was bound at the promoters of the two key genes in eugenol biosynthesis, FaEGS1 and FaEGS2, and activated their transcripts. In summary, our results suggest that FaDOF1 acts as a positive regulator of eugenol metabolism, which provide new insights into the regulatory mechanisms that can improve the quality of strawberry fruit.

The assessment of hull-less barley germplasm for salt tolerance is crucial for future barley breeding programs, as it allows them to be classified for their adaptability to salt stress. Here, the salt tolerance of 224 hull-less barley genotypes was assessed under different NaCl concentrations during the seedling stage. Three hydroponic experiments were conducted, with morpho-physiological characters collected 10, 7 and 10 days after treatment, respectively, for a preliminary, and two subsequent experiments. Results of the first and second experiments revealed that salt-induced the deterioration of various morpho-physiological characters was most pronounced in the number of leaves per plant, shoot heights, root lengths, shoot and root fresh and dry weights. An integrated score (IS) was used to rank the salt tolerance ability and the four highest (X89, X166, X327, and X349; salt-tolerant) and the two lowest ranking accessions (X66 and X386; salt-sensitive) were selected. Principal component analysis (PCA) and hierarchical cluster analysis of the seedling morpho-physiological characteristics among the hull-less barley genotypes showed strong correlations among most characters, which could be used as selection criteria for identifying salt tolerance in the barley germplasm. Furthermore, the combination of IS rank and PCA can be used to identify salt-tolerant and salt-sensitive genotypes of the barley during the seedling stage. These salt-tolerant genotypes hold the potential for developing new barley cultivars with enhanced salt tolerance, and offer opportunities to advance our understanding of the genetic factors involved in barley’s ability to withstand salt stress.

High salinity leads to a reduction in growth, germination, metabolic stability, and production of pepper (Capsicum annuum L.) plants worldwide. GABA priming showed a positive effect on plant growth and development and improved plant stress tolerance. The current study aimed to investigate the effect of exogenous GABA treatments on endogenous GABA shunt pathway in germinating seeds of green bell pepper (Capsicum annuum L.) under salt stress (0, 25, 50, 75, 100 and 200 mM NaCl) through the characterization of seed germination pattern, seedling growth, seed moisture content, GABA shunt metabolite levels (GABA, Alanine, and Glutamate), the level of oxidative damage in terms of the accumulation of reactive oxygen substances and the expression of pepper dehydrin gene (CaDHN3) in response to all salt stress treatments that were examined in this study. Pre-treatment of pepper seeds with GABA improved seed germination by enhancing germination percentage, germination rate, seedling length, seedling fresh and dry weights, seed moisture content, and decreasing mean time to germinate under salt stress. Data showed an increase with positive correlation between internal GABA metabolite, alanine, and glutamate levels and NaCl concentrations in response to all GABA priming treatments. The MDA content increased as NaCl concentration increased under all GABA treatments. However, there was a significant reduction in MDA content in all GABA treatments and hydro-primed pepper seeds when compared to untreated seeds under all NaCl concentrations. The expression of pepper dehydrin gene (CaDHN3) was significantly increased with the increase of NaCl concentrations under all GABA treatments. Priming pepper seeds with exogenous GABA significantly activates GABA shunt and accumulate GABA internally to maintain C: N balance, stabilize internal metabolism, sustain amino acid metabolism, enhance scavenging of reactive oxygen species (ROS) by activating defense mechanisms, and significantly increase the expression of CaDHN3 to prevent lipid peroxidation, maintain metabolic stability and enzymes function and prevent dehydration during seeds germination in response to salt stress.

Plant U-box (PUB) proteins are a type of E3 ligases that are major components of the ubiquitination cascade. PUBs can act as positive or negative regulators in diverse biological processes, including plant responses to biotic and abiotic stresses such as cold stress. However, PUBs in rye (Secale cereale L.), the most cold-resistant winter crop, remain poorly studied. In this study, 100 PUBs in the rye genome and 214 genes in the oat genome were identified. The rye PUBs were classified into seven classes based on protein motifs, and dispersed throughout the whole rye chromosomes with 30 duplication events. Cis-acting regulatory element analysis indicated that all the ScPUB genes possess abiotic stress-responsive elements in their promoter. Further, synteny analysis revealed that the PUBs in rye had higher similarity with wheat and barley, indicating a closer evolutionary distance than that with oat. Rye tissue-specific and abiotic stress-responsive ScPUBs gene expression were examined, and ScPUB6, which is responsive to the cold treatment, was chosen for further analysis. Yeast two-hybrid and bimolecular fluorescence complementation (BiFC) assays revealed three PUB6-interacting proteins (HSP70, 70-kDa heat shock protein; TIG, Trigger factor-like protein; MYB, Myb transcription factor), which might interact in the plasma membrane. Overall, this analysis of U-box E3 ligases could provide valuable information for an improved understanding of the function of PUBs in the cold resistance mechanism of winter crops.

The accumulation of reactive oxygen species (ROS) causes oxidative stress. Long-lived organisms should exhibit greater oxidative stress tolerance than short-lived organisms. For annual plants, such as flax (Linum usitatissimum L.), flowering time and lifespan are positively correlated. On this basis, early-flowering populations of two flax cultivars (Royal [R] and Stormont Cirrus [L]) were predicted to exhibit lower oxidative stress tolerance than normal-flowering controls. Oxidative stress tolerance was assessed by growing plants in water or 30 mM H₂O₂ and measuring i) mitochondrial uncoupling, via measurements of intact leaf respiration in the presence and absence of an uncoupling agent, ii) catalase activity, and iii) peroxide-induced cell membrane damage, via an electrolyte leakage assay. Endogenous salicylic acid (SA) levels were also measured since SA regulates both oxidative stress tolerance and flowering time. Early- and normal-flowering populations did not differ significantly for any of these parameters, suggesting that L. usitatissimum has evolved such low oxidative stress tolerance (as an annual species) that it cannot be further reduced. Differences were found between the two cultivars. Mitochondrial uncoupling was < 100% in R plants but > 100% in L plants, suggesting that oxidative phosphorylation was inhibited by the uncoupling agent in the latter but uncoupled in the former; catalase activity was higher in L plants than R plants, especially in early-flowering populations grown in H₂O₂, suggesting L plants eliminate ROS more rapidly; and peroxide-induced cell membrane damage was higher in L plants than R plants, suggesting that R plants experience less oxidative damage to their membrane phospholipids. SA may play some role in these cultivar-specific responses. As R and L cultivars are bred for seed oil and fibres, respectively, their differences may reflect trade-offs between oxidative stress tolerance and trait selection.

The MAPK cascade, evolutionarily conserved among eukaryotes, plays a crucial role in regulating plant growth, development, and resistance to both biotic and abiotic stresses. However, the gene function of MAPK cascade in foxtail millet (Setaria italica) is poorly studied. In this study, RNA sequencing revealed that the MAPK cascade is the primary enrichment pathway in foxtail millet under salt treatment. Meanwhile, fourteen genes encoding mitogen-activated protein kinase kinases (SiMKKs) were identified and could be categorized into four subfamilies. Under salt treatment, the expression of 11 SiMKKs was upregulated, with SiMKK6-2 in group A showing the most significant increase. SiMKK1 and SiMKK6-1, the other two members of the same subfamily, were also significantly upregulated under salt stress. Overexpression of these three genes in Arabidopsis thaliana reduced the sensitivity of roots to salt stress. The transgenic plants exhibited an increase in lateral roots. Under salt stress, the decrease in primary root length of transgenic plants was significantly less than that of wild-type plants. These three genes are involved in regulating the development of primary and lateral roots of plants, which can maintain better root development to improve plant tolerance to salt stress.