Particle-based hematite crystallization is invariant to initial particle morphology.

SignificanceMany crystallization processes occurring in nature produce highly ordered hierarchical architectures. Their formation cannot be explained using classical models of monomer-by-monomer growth. One of the possible pathways involves crystallization through the attachment of oriented nanocrystals. Thus, it requires detailed understanding of the mechanism of particle dynamics that leads to their precise crystallographic alignment along specific faces. In this study, we discover a particle-morphology-independent oriented attachment mechanism for hematite nanocrystals. Independent of crystal morphology, particles always align along the [001] direction driven by aligning interactions between (001) faces and repulsive interactions between other pairs of hematite faces. These results highlight that strong face specificity along one crystallographic direction can render oriented attachment to be independent of initial particle morphology.

Transcriptional networks regulating suberin and lignin in endodermis link development and ABA response.

Vascular tissues are surrounded by an apoplastic barrier formed by endodermis that is vital for selective absorption of water and nutrients. Lignification and suberization of endodermal cell walls are fundamental processes in establishing the apoplastic barrier. Endodermal suberization in Arabidopsis (Arabidopsis thaliana) roots is presumed to be the integration of developmental regulation and stress responses. In root endodermis, the suberization level is enhanced when the Casparian strip, the lignified structure, is defective. However, it is not entirely clear how lignification and suberization interplay and how they interact with stress signaling. Here, in Arabidopsis, we constructed a hierarchical network mediated by SHORT-ROOT (SHR), a master regulator of endodermal development, and identified 13 key MYB transcription factors (TFs) that form multiple sub-networks. Combined with functional analyses, we further uncovered MYB TFs that mediate feedback or feed-forward loops, thus balancing lignification and suberization in Arabidopsis roots. In addition, sub-networks comprising nine MYB TFs were identified that interact with abscisic acid signaling to integrate stress response and root development. Our data provide insights into the mechanisms that enhance plant adaptation to changing environments.

Symplastic communication in the root cap directs auxin distribution to modulate root development.

Root cap not only protects root meristem, but also detects and transduces the signals of environmental changes to affect root development. The symplastic communication is an important way for plants to transduce signals to coordinate the development and physiology in response to the changing enviroments. However, it is unclear how the symplastic communication between root cap cells affects root growth. Here we exploit an inducible system to specifically block the symplastic communication in the root cap. Transient blockage of plasmodesmata (PD) in differentiated collumella cells severely impairs the root development in Arabidopsis, in particular in the stem cell niche and the proximal meristem. The neighboring stem cell niche is the region that is most sensitive to the disrupted symplastic communication and responds rapidly via the alteration of auxin distribution. In the later stage, the cell division in proximal meristem is inhibited, presumably due to the reduced auxin level in the root cap. Our results reveal the essential role of the differentiated collumella cells in the root cap mediated signaling system that directs root development.

High Mechanical Strength Alloy-like Minerals Prepared by Inorganic Ionic Co-cross-linking.

Alloys often combine different metals to generate superior mechanical properties. However, it is challenging to prepare high mechanical strength minerals with similar strategies. Using calcium carbonate (CaC) and calcium phosphate (CaP) as examples, this work synthesizes a group of compounds with the chemical formulas Ca(CO3 )x (PO4 )2(1- x )/3 (0 < x < 1, CaCPs) by cross-linking ionic oligomers. Unlike mixtures, these CaCPs exhibit a single temperature for the phase transition from amorphous to crystallized CaC (calcite) and CaP (hydroxyapatite). By heat-induced synchronous crystallization, dual-phase CaC/CaP with continuous crystallized boundaries are resembled to alloy-like minerals (ALMs). The mechanical properties of the ALMs are adjusted by tailoring their chemical compositions to reach a hardness of 5.6 GPa, which exceed those of control calcite and hydroxyapatite samples by 430% and 260%, respectively. This strategy expands the chemical scope of inorganic materials and holds promise for preparing high-performance minerals.

Magnaporthe oryzae CK2 Accumulates in Nuclei, Nucleoli, at Septal Pores and Forms a Large Ring Structure in Appressoria, and Is Involved in Rice Blast Pathogenesis.

Magnaporthe oryzae (Mo) is a model pathogen causing rice blast resulting in yield and economic losses world-wide. CK2 is a constitutively active, serine/threonine kinase in eukaryotes, having a wide array of known substrates, and involved in many cellular processes. We investigated the localization and role of MoCK2 during growth and infection. BLAST search for MoCK2 components and targeted deletion of subunits was combined with protein-GFP fusions to investigate localization. We found one CKa and two CKb subunits of the CK2 holoenzyme. Deletion of the catalytic subunit CKa was not possible and might indicate that such deletions are lethal. The CKb subunits could be deleted but they were both necessary for normal growth and pathogenicity. Localization studies showed that the CK2 holoenzyme needed to be intact for normal localization at septal pores and at appressorium penetration pores. Nuclear localization of CKa was however not dependent on the intact CK2 holoenzyme. In appressoria, CK2 formed a large ring perpendicular to the penetration pore and the ring formation was dependent on the presence of all CK2 subunits. The effects on growth and pathogenicity of deletion of the b subunits combined with the localization indicate that CK2 can have important regulatory functions not only in the nucleus/nucleolus but also at fungal specific structures such as septa and appressorial pores.

Oxygen vacancy regulation on tungsten oxides with specific exposed facets for enhanced visible-light-driven photocatalytic oxidation.

Introduced oxygen vacancy on WO3 with specific exposed facets was prepared through facile solvothermal treatment and different cooling methods. We demonstrated that the density of oxygen defects could be regulated by different cooling methods and speculated that oxygen vacancy with appropriate concentration range could promote photocatalytic activity through suppressing the recombination of photo-induced carriers. The specific exposed facets with higher oxidation efficiency were prepared by solvothermal reaction. WO3-A treated by air cooling exhibits the best photocatalytic oxygen evolution rate at 500 µmol g-1 h-1 using AgNO3 as sacrifice agent under visible light (λ > 400 nm) without any co-catalysts, which is about 2 times higher than WO3-N without oxygen defects. This strategy, using different cooling methods to regulate oxygen vacancy concentration on tungsten oxides, could contribute to the design of other high efficiency photocatalysts.