Characterization of a Novel Polysaccharide Derived from Rhizospheric Paecilomyces vaniformisi and Its Mechanism for Enhancing Salinity Resistance in Rice Seedlings.

Soil salinity is an important limiting factor in agricultural production. Rhizospheric fungi can potentially enhance crop salinity tolerance, but the precise role of signaling substances is still to be systematically elucidated. A rhizospheric fungus identified as Paecilomyces vaniformisi was found to enhance the salinity tolerance of rice seedlings. In this study, a novel polysaccharide (PPL2b) was isolated from P. vaniformisi and identified as consisting of Manp, Glcp, GalpA, and Galp. In a further study, PPL2b showed significant activity in alleviating salinity stress-induced growth inhibition in rice seedlings. The results indicated that under salinity stress, PPL2b enhances seed germination, plant growth (height and biomass), and biochemical parameters (soluble sugar and protein contents). Additionally, PPL2b regulates genes such as SOS1 and SKOR to decrease K+ efflux and increase Na+ efflux. PPL2b increased the expression and activity of genes related to antioxidant enzymes and nonenzyme substances in salinity-induced oxidative stress. Further study indicated that PPL2b plays a crucial role in regulating osmotic substances, such as proline and betaine, in maintaining the osmotic balance. It also modulates plant hormones to promote rice seedling growth and enhance their tolerance to soil salinity. The variables interacted and were divided into two groups (PC1 77.39% and PC2 18.77%) based on their relative values. Therefore, these findings indicate that PPL2b from P. vaniformisi can alleviate the inhibitory effects of salinity stress on root development, osmotic adjustment, ion balance, oxidative stress balance, and growth of rice seedlings. Furthermore, it suggests that polysaccharides produced by rhizospheric fungi could be utilized to enhance crop tolerance to salinity.

Evaluation of negative effect of Naphthenic acids (NAs) on physiological metabolism and polycyclic aromatic hydrocarbons adsorption of Phragmites australis.

Toxic substances in the environment disturb the adsorption of pollutants in plants but little is known about the underlying mechanisms of these processes. This study evaluated the PAH adsorption by Phragmites australis under NAs stress. Results showed that Naphthenic acids (NAs) significantly decreased the adsorption of PAHs and had higher selectivity for type and structure. P. australis root cell growth and mitosis were significantly affected by NAs, which was accompanied by serious disturbances in mitochondrial function. The physiological evaluation showed the NAs could increase Reactive Oxygen Species (ROS) accumulation by around 16-fold and cause damage to the root cell normal redox equilibrium. The levels of three key related antioxidants, PLA, CAT and POD, decreased significantly to 35-50% under NAs stress and were dependent upon NAs concentration. Furthermore, NAs could significantly change the concentration and species of root exudates of P. ausralis. Autotoxic substances, including alcohol and amines, increased by 28.63% and 23.96, respectively. Sixteen compounds were identified and assumed as potential biomarkers. Galactonic, glyceric, and octadecanoic acid had the general effect of activating PAH in soil. The global view of the metabolic pathway suggests that NAs influenced the citric acid cycle, fatty acid synthesis, amino acid metabolism and the phenylpropanoid pathway. Detection data results indicated that the energy products cause hypoxia and oxidative stress, which are the main processes under the NAs. Furthermore, verification of these processes was fulfilled through gene expression and biomarkers quantification. Our results provide novel metabolic insights into the mechanisms of PAHs adsorption by P. australis under NAs disturbance, suggesting that monitoring NAs in phytoremediation applications is necessary.

A new chitosan sub-micron and encapsulated Iturin A with enhanced antifungal activity against Ceratocystis fimbriata and Rhizopus strolonifer.

Iturin A is a natural antifungal agent that is widely used in the agriculture and food industries. In the present study, a new modified chitosan sub-micron, succinaldehydic acid (SAC) - chitosan (CS) system was synthesised by microwave irradiation and then as a carrier for capsulation of Iturin A (SAC-CS-IA). The structures of SAC-CS and SAC-CS-IA were characterised by SEM, NMR and FTIR. The size distribution suggested that the average size of SAC-CS and SAC-CS-IA was from 1.5 to 2.5 µm. An encapsulation efficiency of 92.02% under an adaptive pH (pH = 5) and time (5.5 h) was used. The study of release kinetics shows that about 80% of Iturin A was released in 25 days. An antifungal activity assay indicated that SAC-CS-IA exhibited higher antifungal activity against Ceratocystis fimbriata and Rhizopus strolonifer with 75.05 ± 3.24% and 80.54 ± 2.65%, respectively. The results indicate that the SAC-CS can improve the stability of IA on heat and pH with a wide range and tolerance most of enzymes. Actual tuber storage suggested that SAC-CS-IA can significantly inhibit pathogen fungal infection and reduce toxin product. Meanwhile, SAC-CS-IA could retain the water, starch, and soluble sugar contents. Low residue assay indicated that SAC-CS-IA could be used as an antifungal and anti-rotting agent in agriculture and food applications.