Self-Reduction-Related Defects, Long Afterglow, and Mechanoluminescence in Centrosymmetric Li2ZnGeO4:Mn2.

Mechanoluminescent materials have shown great application potential in the fields of stress detection, anti-counterfeiting, and optical storage; however, its development is hindered by the unclear mechanism. Different from the mainstream exploration of new mechanoluminescent materials in non-centrosymmetric structures, a centrosymmetric mechanoluminescent material Li2ZnGeO4:Mn2+ is synthesized by a standard high-temperature solid-state reaction in an ambient atmosphere. Combined with the Rietveld refinement, photoluminescence, electron spin resonance, and X-ray photoelectron spectroscopy, it is proved that the increase in oxygen vacancies is accompanied by the self-reduction process from Mn4+ to Mn2+, and the mechanism of mechanoluminescence is clarified through the afterglow and thermoluminescence spectra. The carriers trapped by the shallow traps participate in the mechanoluminescence process through the tunneling effect, while the carriers trapped by the deep traps take part in the mechanoluminescence process via conduction band or tunneling. A signature anti-counterfeiting application is designed using the new mechanoluminescent material Li2ZnGeO4:0.004Mn2+. Utilizing the afterglow characteristics of Li2ZnGeO4:xMn2+ phosphors, we designed an intelligent long-persistent luminescence quick response code (QR-code) and visualized information encoding/decoding model, which provides a fast, simple, and effective method for information encryption, transformation, and dynamic anti-counterfeiting. This study not only analyzes the self-reduction and mechanoluminescence processes in detail but also breaks the limitation of crystal symmetry and provides a new strategy for the exploration of novel mechanoluminescent materials.

Construction of a novel mechanoluminescent phosphor Li2MgGeO4:xMn2+ by defect control.

Lattice defect plays a significant role in the optical properties of elastic mechanoluminescent materials, which could be modulated by cationic non-equivalent replacement. Here, a series of novel mechanoluminescent phosphors Li2-xMgGeO4:xMn2+ (0 ≤ x ≤ 0.025) were synthesized via a high-temperature solid-state reaction method in an ambient atmosphere. The defect type and its relationship with optical perfomance were clarified via X-ray photoelectron spectroscopy, electron spin resonance, and thermoluminescent spectroscopy. Along with the introduction of Mn ions, the trap levels of oxygen vacancies become shallow, which are beneficial to produce long afterglow and mechanoluminescence. This study offers a feasible approach for developing new functional materials via defect control in self-reduction systems.

Overexpression of the Tibetan Plateau annual wild barley (Hordeum spontaneum) HsCIPKs enhances rice tolerance to heavy metal toxicities and other abiotic stresses.

BACKGROUND: The calcineurin B-like protein (CBL) and CBL-interacting protein kinase (CIPK) signaling system plays a key regulatory role in plant stress signaling. The roles of plant-specific CIPKs, essential for CBL-CIPK functions, in the response to various abiotic stresses have been extensively studied so far. However, until now, the possible roles of the CIPKs in the plant response to heavy metal toxicities are largely unknown. RESULTS: In this study, we used bioinformatic and molecular strategies to isolate 12 HsCIPK genes in Tibetan Plateau annual wild barley (Hordeum spontaneum C. Koch) and subsequently identified their functional roles in the response to heavy metal toxicities. The results showed that multiple HsCIPKs were transcriptionally regulated by heavy metal toxicities (e.g., Hg, Cd, Cr, Pb, and Cu) and other abiotic stresses (e.g., salt, drought, aluminum, low and high temperature, and abscisic acid). Furthermore, the ectopic overexpression of each HsCIPK in rice (Oryza sativa L. cv Nipponbare) showed that transgenic plants of multiple HsCIPKs displayed enhanced tolerance of root growth to heavy metal toxicities (Hg, Cd, Cr, and Cu), salt and drought stresses. These results suggest that HsCIPKs are involved in the response to heavy metal toxicities and other abiotic stresses. CONCLUSIONS: Tibetan Plateau annual wild barley HsCIPKs possess broad applications in genetically engineering of rice with tolerance to heavy metal toxicities and other abiotic stresses.

[Calcium sensors and their stress signaling pathways in plants].

Calcium (Ca2+) signals are a core regulator of plant growth and development and responses to environmental cues and thus highlighted in plant physiological and stress biology. External stimuli trigger specifically intracellular spatial and temporal [Ca2+]cyt variations in plant cells. This [Ca2+]cyt variations will be sensed and decoded by calcium sensors and, in turn, calcium sensor interacting proteins transmit resulting signals to the downstream effectors to activate the expression of early response genes or promote ion channel activities, finally leading to specific stress responses. How the plant cell distinguishes different types or intensity of external stimuli through sensing intracellular spatial and temporal variations of Ca2+ signals is a scientific issue recently highlighted by plant biologists. This review summarized recent advances in the research field of plant calcium sensors, including the structural characteristics, functional roles, and stress signaling path-ways of calcium-dependent protein kinases (CDPKs), calmodulins (CaMs), calmodulin-like proteins (CMLs), and cal-cineurin B-like proteins (CBLs) and their interacting kinases (CIPKs), and moreover provided new insights and perspectives.