Small G Protein StRab5b positively regulates potato resistance to Phytophthora infestans.

Rabproteins are the largest members of the small G protein family and are widely distributed in eukaryotes. It comprises eight subfamilies and is responsible for regulating vesicle transport, plant growth and development, and biotic and abiotic stress responses. In this study, the small G protein gene StRab5b was cloned from potato, and its biological information, expression profile and induced expression level, overexpression and gene silencing were examined on regulating potato resistance to Phytophthora infestans using PCR, qPCR and Virus-induced gene silencing (VIGS). Our results indicate that the amino acid of StRab5b shows the highest and lowest homology with NbRab5b in N. benthamiana and StRab in potato respectively. StRab5b expression varied among different potato tissues and varieties, and was induced by P. infestans infection. Transiently ectopic expression of StRab5b in N. benthamiana enhanced its resistance to P. infestans, whereas, silencing of StRab5b and its homologous gene facilitated pathogen infection in potato and N. benthamiana respectively. Furthermore, stable expression of the StRab5b gene in potatoes enhanced its redox-stress response capacity, as manifested by the accumulation of H2O2 in infected leaves and subsequent increase in the activity and expression of ROS scavenging enzymes, thereby attenuating the development of P. infestans and ultimately reducing the lesions on infected potato leaves. In addition, the LOX gene transcripts and JA level were upregulated rapidly after inoculation with P. infestans. Collectively, our results suggest that StRab5b positively regulates the resistance against potato late blight (PLB) via JA-mediated defense signaling pathway.

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We examined the effects of shading photosynthetic characteristics, yield, and tolerance to low light in two potato varieties (Jizhangshu 12 and Jizhangshu 8) at four growth stages (seedling, seedling/budding, budding/early flowering and flowering/harvest). There were three shading treatments (0(CK), 20% and 50%). The results showed that at both 20% and 50% shading rates, the SPAD value (a measure of leaf cellular chlorophyll content) of the two varieties decreased significantly at the seedling stage compared with CK treatment. No significant change in the SPAD value occurred at the seedling/budding stage or the budding/early-flowering stage. However, the SPAD value increased marginally after shading at the initial flowering stage. Under the 50% shading regime, the SPAD values of both varieties followed the same trend as the 20% regime. The range of changes at different growth stages remained similar. The only exception was that shading at the beginning of flowering increased SPAD value. Shading had little effect on leaf stomatal conductance (gs) at each developmental stage. There was no significant difference between all treatments and the control, except that the gsvalue of Jizhangshu 8 decreased significantly (43.9%) compared with the control under 50% shading at the beginning of flowering. After the shading treatment, the intercellular CO2 concentration (Ci) of leaves showed an upward trend. 50% shading at the seedling and seedling/budding stages could significantly increase Ci, but not at other stages. The net photosynthetic rate (Pn) of the four periods were all decreased after 15 d of shading. The Pn reduction of the two varieties, 50% shading, was greater than 20% shading. The decline range of Pn of Jizhangshu 12 was less than that of Jizhangshu 8 at all stages, except for that at the seedling stage. The yield of shading treatments decreased in all four stages, with the decrease rate of 50% shading treatment being greater than that of the 20% shading treatment. 'Jizhangshu 12'was not tolerant to low light at the seedling stage but performed better than 'Jizhangshu 8' at other stages. The comprehensive analysis of two test varieties implied that varieties with strong tolerance to low light experienced a smaller boost in intercellular CO2 concentration and a smaller drop in net photosynthetic rate, stomatal conductance, and yield post-shading.

In vitro and in vivo release of diclofenac sodium-loaded sodium alginate/carboxymethyl chitosan-ZnO hydrogel beads.

To control release of drugs sensitive to gastrointestinal (GI) environmental effects or irritating to stomach, such as diclofenac sodium (DS), sodium alginate (SA) hydrogel beads are gaining considerable attention gradually. However, due to high swelling ratio, the sustained release performance of SA hydrogel is still far from satisfactory. The objective of this research was to develop new drug delivery device based on SA and ZnO nanoparticles (ZnO NPs). ZnO NPs were prepared by direct precipitation method, and carboxymethyl chitosan (CMCS) acted as stabilizing agent to dominate the preparation of ZnO NPs. The incorporation of CMCS-ZnO NPs resulted in slower and sustained release of DS in vitro. In vivo pharmacokinetics studies showed the bioavailability of DS was better after oral administration of DS-loaded SA/CMCS-ZnO hydrogel beads. These results suggested that SA/CMCS-ZnO hydrogel beads will be a prospective material for loading drugs sensitive to GI environmental effects or irritating to stomach.

Preparation and characterization of multilayer films composed of chitosan, sodium alginate and carboxymethyl chitosan-ZnO nanoparticles.

To deal with serious environmental pollution resulting from plastic packaging materials, biodegradable films using chitosan (CS) are gaining considerable increase gradually. However, chitosan films lack important properties to meet the preserved demands. This study aimed to develop new bio-based films incorporated with carboxymethyl chitosan-ZnO (CMCS-ZnO) nanoparticles and sodium alginate (SA) to overcome the weakness of CS films. CMCS-ZnO nanoparticles were successfully synthesized in the matrix of CMCS through direct precipitation method, which showed an average diameter of 100 nm. Multilayer films with CS film as the outer layer and SA film as the inner layer were prepared by solution casting method. The addition of CMCS-ZnO nanoparticles led to enhanced tensile strength, and to better water vapor resistance. The as-prepared films exhibited distinctive antibacterial activity against S. aureus and E. coli. The results suggested that the as-prepared film is expected to be a promising material for food packaging.

Characterization, release, and antioxidant activity of curcumin-loaded sodium alginate/ZnO hydrogel beads.

In this study, we fabricated a series of novel sodium alginate/ZnO hydrogel beads to optimize the release profile of curcumin (Cur) and to avoid the burst release associated with pure hydrogels, which were used to mitigate the weaknesses of Cur, such as rapid physiological clearance and sensitivity to ultraviolet (UV) light and alkaline solutions. The results show that the composite hydrogel beads exhibit good pH sensitivity and controlled-release capacity, which could prolong the residence time of Cur in the gastrointestinal tract. After exposure to UV irradiation for 6 h, the 1,1-Diphenyl-2-picrylhydrazyl (DPPH) scavenging capacity of Cur-loaded hydrogel beads was decreased by only 13.70%, whereas that of pure Cur decreased by 62.04% under the same conditions; therefore, the encapsulated Cur showed a higher antioxidant activity. The composite hydrogel beads protected the Cur from light degradation and can therefore prolong the antioxidant activity of Cur. These results are beneficial for the design of delivery systems to entrap and control the release of unstable drugs.