There is a direct link between the increasing human population and soil degradation that raises current and future food security concerns. Soil amelioration using beneficial microorganisms, particularly arbuscular mycorrhizal fungi (AMF), is essential and pragmatic. AMF produces glomalin that also contributes to the mitigation of soil degradation. However, studies on the ecological role of glomalin are scattered and patchy, and no evident overview exists. We fill this knowledge gap by a systematic and comprehensive literature review of the glomalin’s role in the context of soil degradation problems, including soil desertification, fertility loss, and pollution. Glomalin improves soil physical properties, carbon sequestration, nutrient contents, microbial activities, stabilizes pollutants, and eventually assists ecological restoration. Such a positive impact of glomalin is thought to be through its prevailing impact on soil; by acting as a substrate for microbes, a gluing agent for aggregate formation, chelation of heavy metals and toxic pollutants, and improving carbon sequestration through long-term persistence (≥42 years) in soil. Given the production of glomalin as a result of an interplay between plant, soil, and AMF, hence, we provide specific strategies at the plant, soil, and microbial level to improve glomalin concentration. Specifically, we can develop genetically modified or hybrid plants for higher rhizodeposition and promotes soil microbial diversity through the inoculation of AMF and beneficial bacteria. We highlight the research gaps and discuss prospects. This knowledge will improve our understanding of glomalin, stimulate future research, and be useful for the sustainable restoration of degraded lands. Graphical Abstract

Multiple environmental stresses adversely affect plant growth and development. Plants under multiple stress condition trigger cascade of signals and show response unique to specific stress as well as shared responses, common to individual stresses. Here, we aim to identify common and unique genetic components during stress response mechanisms liable for cross-talk between stresses. Although drought and cold stress have been widely studied, insignificant information is available about how their combination affects plants. To that end, we performed meta-analysis and co-expression network comparison of drought and cold stress response in Arabidopsis thaliana by analyzing 390 microarray samples belonging to 29 microarray studies. We observed 6120 and 7079 DEGs (differentially expressed genes) under drought and cold stress respectively, using Rank Product methodology. Statistically, 28% (2890) DEGs were found to be common in both the stresses (i.e.; drought and cold stress) with most of them having similar expression pattern. Further, gene ontology-based enrichment analysis have identified shared biological processes and molecular mechanisms such as—‘photosynthesis’, ‘respiratory burst’, ‘response to hormone’, ‘signal transduction’, ‘metabolic process’, ‘response to water deprivation’, which were affected under cold and drought stress. Forty three transcription factor families were found to be expressed under both the stress conditions. Primarily, WRKY, NAC, MYB, AP2/ERF and bZIP transcription factor family genes were highly enriched in all genes sets and were found to regulate 56% of common genes expressed in drought and cold stress. Gene co-expression network analysis by WGCNA (weighted gene co-expression network analysis) revealed 21 and 16 highly inter-correlated gene modules with specific expression profiles under drought and cold stress respectively. Detection and analysis of gene modules shared between two stresses revealed the presence of four consensus gene modules.

We explore optical activity in thin films and bulk of type-I and type-II Weyl semimetals (WSMs), and demonstrate the existence of a giant Kerr effect in both. In time reversal symmetry broken WSM thin films, the polarization rotation is caused by the optical Hall conductivity including the anomalous Hall term. The Kerr angle is found to be $\propto Q/\omega$, with $Q$ and $\omega$ being the Weyl node separation and the optical frequency, respectively. In contrast, the optical activity in the bulk WSM is dominated by axion electrodynamics, which persists even in the Pauli-blocked regime of no optical transitions. In bulk WSMs, $Q$ acts analogously to the magnetization in magnetic materials, leading to a large polar Kerr effect (linear in $Q$), when light is incident on the WSM surface without Fermi arc states, and the Voigt effect (quadratic in $Q$), when light is incident on surface with Fermi arc states.