Remediation of pear iron chlorosis by nanocellulose-iron chelation and mechanisms

Background: Nanocrystal cellulose has a strong ability to chelate iron and the nanocomposite possesses strong adsorptive property. Iron deficiency chlorosis (IDC) is a mineral disorder that weakens pear photosynthesis and cause a significant decline in plant yield and quality. Conventional methods to control IDC are generally due to low efficiency and overuse of chemicals. The purpose of this study was to explore the capability of nanocellulose (NC)-Fe chelate to remediate pear IDC. Acidic hydrolyzed NCs were chelated with Fe (NCFe) based on the net charge density of the components. Foliar application of NCFe was employed to pre-etiolated seedlings of Pyrus betulifolia as a plant material. The ability of NCFe to promote active iron content (CFe), photosynthesis rate, and relative gene expression was studied. Results: Nanocrystal cellulose prepared by acidic hydrolysis exhibit rod-like whiskers carrying on negative charges. When NCs were mixed with FeSO4, the NCFe particles maintained a small, whisker-like morphology with small dots (Fe) on the surface of the NC particles. The Z-average hydrodynamic diameter and zeta potential of the NC whiskers measured by DLS were 84.3 ± 0.2 nm and -47.3 ± 1.7 mV, respectively. The particle size and zeta potential of NCFe were 107.4±3.0 nm and -9.7±0.4 mV, respectively. The results showed that NCFe could significantly mitigate IDC in seedlings by increasing CFe, photosynthesis parameters, major physiological indicators, and regulating the expression of key enzymes. When NCFe was prepared at a NC-to-Fe charge density ratio of 1:3,000, CFe and chlorophyll contents were enhanced by approximately 9 times and 72.7%, respectively; the major physiological indicators were all significantly increased. Interestingly, NCFe treatment significantly downregulated the expression of the pectin methylesterase gene (PbPME) and upregulated the expression of the ferritin gene (PbFER) to increase CFe.Conclusion: NCs have strong potential to promote plant photosynthesis when chelated with Fe. The remediation capability of NCFe to IDC is attributed to the enhancement of photosynthesis parameters and indicators. NCFe treatment significantly downregulated the expression of the PME gene (PbPME) and upregulated the expression of the ferritin gene (PbFER) to increase the active iron content. This finding will provide a good alternative and a complementary strategy for Fe-chelate applications in plant iron chlorosis management.

Distinctive Roles of Two Acinetobactin Isomers in Challenging Host Nutritional Immunity

Acinetobacter baumannii has acquired antibiotic resistance at an alarming rate, and it is becoming a serious threat to society, particularly due to the paucity of effective treatment options. Acinetobactin is a siderophore of Acinetobacter baumannii , responsible for active iron supply, and it serves as a key virulence factor to counter host nutritional immunity during infection.

Spin-Crossover in Iron(II) Complexes of N,N′-Disubstituted 2,6-Bis(Pyrazol-3-yl)Pyridines: An Effect of a Distal Substituent in the 2,6-Dibromophenyl Group

A series of new bis(pyrazol-3-yl)pyridines (LR) N,N′-disubstituted by 4-functionalized 2,6-dibromophenyl groups have been synthesized to study the effect of a distal substituent on the spin-crossover (SCO) behaviour of the iron(II) complexes [Fe(LR)2](ClO4)2 by variable-temperature magnetometry, NMR spectroscopy, and X-ray diffraction. The SCO-assisting tendency of the substituents with different electronic and steric properties (i.e., the bromine atom and the methyl group) in the para-position of the 2,6-dibromophenyl group is discussed. Together with earlier reported SCO-active iron(II) complexes with N,N′-disubstituted bis(pyrazol-3-yl)pyridines, these new complexes open the way for this family of SCO compounds to emerge as an effective ‘tool’ in revealing structure–function relations, a prerequisite for successful molecular design of switchable materials for future breakthrough applications in sensing, switching, and memory devices.