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Maize is a valuable raw material for feed and food production. Healthy seed germination is important for improving the yield and quality of maize. Seed aging occurs relatively fast in crops and it is a process that delays germination as well as reduces its rate and even causes total loss of seed viability. However, the physiological and transcriptional mechanisms that regulate maize seeds, especially aging seed germination remain unclear. Coronatine (COR) which is a phytotoxin produced by Pseudomonas syringae and a new type of plant growth regulator can effectively regulate plant growth and development, and regulate seed germination. In this study, the physiological and transcriptomic mechanisms of COR-induced maize seed germination under different aging degrees were analyzed. The results showed that 0.001–0.01 μmol/L COR could promote the germination of aging maize seed and the growth of primary roots and shoots. COR treatment increased the content of gibberellins (GA3) and decreased the content of abscisic acid (ABA) in B73 seeds before germination. The result of RNA-seq analysis showed 497 differentially expressed genes in COR treatment compared with the control. Three genes associated with GA biosynthesis (ZmCPPS2, ZmD3, and ZmGA2ox2), and two genes associated with GA signaling transduction (ZmGID1 and ZmBHLH158) were up-regulated. Three genes negatively regulating GA signaling transduction (ZmGRAS48, ZmGRAS54, and Zm00001d033369) and two genes involved in ABA biosynthesis (ZmVP14 and ZmPCO14472) were down-regulated. The physiological test results also showed that the effects of GA and ABA on seed germination were similar to those of high and low-concentration COR, respectively, which indicated that the effect of COR on seed germination may be carried out through GA and ABA pathways. In addition, GO and KEGG analysis suggested that COR is also highly involved in antioxidant enzyme systems and secondary metabolite synthesis to regulate maize seed germination processes. These findings provide a valuable reference for further research on the mechanisms of maize seed germination. [ABSTRACT FROM AUTHOR]

Aims: In this study, a novel plant growth regulator 2,4-dichloroformamide cyclopropane acid (B2) was used to explore its effects on wheat stalk morphology, chemical composition, anatomical structure, crushing strength and their relationship with lodging resistance. The effects of stem quality change on grain filling and yield were further discussed. Methods: We conducted a series of experiments, including determinations of internode morphology and breaking resistance, analyses of chemical composition and hormone content, observation of internode anatomy, and measurement of grain filling rate, to explore the effects of internode developmental changes induced by B2 treatment on grain filling. Results: Spraying 150 μmol·L−1 B2 at jointing stage significantly decreased plant height, height of center of gravity, basal internode and cell length, while increased stem diameter, wall thickness of basal second internode, cortex thickness, vascular bundle transverse section area and cell cross-sectional area, which resulted in higher breaking strength and culm lodging resistance index. B2 also significantly reduced the content of gibberellin in the second basal internode, and increased the accumulation of lignin and cellulose, thus forming a shorter and stronger stalk. Correlation analysis showed that stem outer diameter, stem wall thickness, cellulose and lignin content were significantly and positively correlated with stem breaking strength. The improvement of stalk structure, especially vascular bundle area, increased bleeding sap, which contributed to grain filling and final yield formation. Conclusions: Lodging resistance and average grain-filling rate can be enhanced by spraying B2 at wheat jointing stage due to the improvement of culm structure, which is conducive to further increase of yield. [ABSTRACT FROM AUTHOR]

Heat stress has detrimental impacts on wheat growth and yield formation. Conferring heat tolerance through applying plant growth regulators is a feasible strategy to reduce loss. Gamma aminobutyric acid (GABA) is a four-carbon non-proteinogenic amino acid existing in organisms and accumulates in response to stress. In this study, spring wheat Liaochun17 and winter wheat Jingdu 40 were used to investigate the function of exogenous GABA on the heat tolerance of wheat seedlings. Data displayed that GABA treatment not only reduced the production of reactive active oxygen (ROS), but also improved the scavenging capacity of diphenyl picryl phenyl hydrazine active oxygen under heat stress, thus alleviating the accumulation of malondialdehyde and the damage of cell membrane. In addition, analysis of protein and amino acids revealed that GABA effectively promoted the accumulation of soluble protein and coordinated amino acid homeostasis. Summarily, our current findings revealed that GABA strengthened the resistance of wheat seedling to heat stress by maintaining the metabolism balance of ROS and amino acids. [ABSTRACT FROM AUTHOR]

Coronatine (COR) is a phytotoxin produced by Pseudomonas syringae and is a functional analogue of the bioactive hormone JA-Ile, which is widely involved in plant defence responses. In this study, we explored the effects of exogenous applications of COR on tobacco plants under polyethylene glycol-induced drought stress. Compared with control (CK), COR-treated tobacco plants exhibited higher leaf relative water content and better photosynthetic performance under drought exposure. Ultrastructural examination revealed that drought led to stomatal closure and disorganization of granum stacking in the chloroplasts (with obvious accumulation of plastoglobuli), and mitochondria in the CK samples presented injured cristae. In the leaf tissue of the COR-treated plants, regularly stacked granum thylakoids, few plastoglobuli and intact mitochondrial membranes and cristae were observed. Totals of 1803 and 6207 differentially expressed genes (DEGs) were identified between the samples from the COR-treated and CK plants under well-watered and drought conditions. Functional annotation analysis revealed that these DEGs were involved mainly in plant hormone signal transduction, cellular carbohydrate metabolic processes and photosynthesis processes. Six hundred forty transcription factor genes were also identified among the DEGs. This study provides a global view of COR-induced drought stress tolerance in tobacco from both physiological and transcriptional aspects. [ABSTRACT FROM AUTHOR]

In this study, Bi2O3 nanoparticles are prepared via an impregnation method and modified using multi-walled carbon nanotubes (MWCNTs) and PW12. XRD reveals that the prepared Bi2O3 corresponded to the monoclinic α-phase. SEM results reveal that the composite consists of a series of nanosheets with flower-like structures. In this study, malachite green (MG) is used as a simulated contaminant to test the degradation capability of the compound under sunlight, and the effect of PW12 doping on the photocatalytic properties of the sample is investigated. The results show that the degradation kinetic constant of 0.3 PW12/MWCNTs/Bi2O3 (0.8125 h−1) is about 3 times that of Bi2O3 (0.2767 h−1). The ternary complex containing 30% PW12 has a degradation rate of 95% in 2.5 h. h+ and · O 2 - were the major active species in the photocatalytic degradation of MG. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) originate from primary transcripts (pri-miRNAs) with characteristic stem-loop structures, and their accurate processing is required for the production of functional miRNAs. Here, using the pri-miR-166 family in Arabidopsis thaliana as a paradigm, we report the crucial role of pri-miRNA terminal loops in miRNA biogenesis. We found that multibranched terminal loops in pri-miR-166s substantially suppress miR-166 expression in vivo. Unlike canonical processing of pri-miRNAs, terminal loop-branched pri-miRNAs can be processed by Dicer-like 1 (DCL1) complexes bidirectionally from base to loop and from loop to base, resulting in productive and abortive processing of miRNAs, respectively. In both cases, DCL1 complexes canonically cut pri-miRNAs at a distance of 16-17 bp from a reference single-stranded loop region. DCL1 also adjusts processing sites toward an internal loop through its helicase domain. These results provide new insight into the poorly understood processing mechanism of pri-miRNAs with complex secondary structures. [ABSTRACT FROM AUTHOR]

Coronatine (COR) is a phytotoxin produced by Pseudomonas syringae. Its structure is similar to Jasmonates, which play a number of diverse roles in plant defense. Both have the COI1 plant receptor, so coronatine can manipulate plant hormone signaling to access nutrients and counteract defense responses. In addition to the hormone system, coronatine affects plant nitrogenous metabolism and chloroplast ultrastructure. In this study, we first examined a typical nitrogen-losing phenotype, and used the polyacrylamide gel approach to demonstrate soluble total protein patterns in a time-course experiment under different temperature conditions. We then employed dimensional gel electrophoresis technology (2-DE) and MALDI-TOF-MS to sequester and identify the sensitive proteins. We found a total of 27 coronatine sensitive proteins, 22 of which were located in the chloroplast and 6 of which were directly involved in photosynthesis. Finally, we measured levels of chlorophyll and photosynthetic performance to reveal the phenotypic effect of these proteins. Taken together, these results demonstrated that coronatine enhanced heat tolerance by regulating nitrogenous metabolism and chloroplast ultrastructure to maintain photosynthetic performance and reduce yield loss under heat stress. [ABSTRACT FROM AUTHOR]