Xanthomonas as a model system for studying pathogen emergence and evolution.

In this review, we highlight studies where whole genome sequencing, comparative genomics and population genomics have provided unprecedented insights into past and ongoing pathogen evolution. These include new understanding of adaptive evolution of secretion systems and their effectors. We focus on Xanthomonas pathosystems that have seen intensive study and improved our understanding of pathogen emergence and evolution, particularly in the context of host specialization: citrus canker, bacterial blight of rice, and bacterial spot of tomato and pepper. Across pathosystems, pathogens appear to follow a pattern of bursts of evolution and diversification that impact host adaptation. There remains a need for studies on the mechanisms of host range evolution and genetic exchange among closely related but differentially host-specialized species, and to start moving beyond the study of specific strain and host cultivar pairwise interactions to thinking about these pathosystems in a community context.

Estimation of forest canopy density through Geospatial Technology-a case study on Sathyamangalam Forest, Erode District, Tamil Nadu.

The term forest canopy density (FCD) refers to one of the important criteria used to evaluate forest's ecological health. It plays a significant role in assessing the health of the forest and serves as a key landmark for potential management actions. The canopy coverage or crown cover is referred to the percentage of the forest floor that is covered by the vertical projection of tree crowns and necessary for monitoring the condition of the forest. The present study aims to estimate the forest canopy density (FCD) through Geospatial Techniques for Sathyamangalam Forest for the period between 2016 and 2022 with SENTINEL 2A satellite data. The weighted overlay analysis method was implemented with biophysical parameters, namely, Normalize Difference Vegetation Index (NDVI), Advanced Vegetation Index (AVI), Shadow Index (SI), and Soil Bareness Index (SBI) to analyze the state of the forest and its activity. The results observed significantly that the forest canopy with 158.60 km2 in 2016 which is increased to 190.37 km2 in 2018 (1.14%) then suddenly decreased to 134.85 km2 in 2020 (2.47%). The forest canopy has recovered some of its original area with 168.83 km2 through better environmental conditions during 2021-2022 (1.52%). Therefore, Geospatial Technology plays a significant role in estimating recent changes in regional forest.

Transcriptome profiling of type VI secretion system core gene tssM mutant of Xanthomonas perforans highlights regulators controlling diverse functions ranging from virulence to metabolism.

IMPORTANCE: T6SS has received attention due to its significance in mediating interorganismal competition through contact-dependent release of effector molecules into prokaryotic and eukaryotic cells. Reverse-genetic studies have indicated the role of T6SS in virulence in a variety of plant pathogenic bacteria, including the one studied here, Xanthomonas. However, it is not clear whether such effect on virulence is merely due to a shift in the microbiome-mediated protection or if T6SS is involved in a complex virulence regulatory network. In this study, we conducted in vitro transcriptome profiling in minimal medium to decipher the signaling pathways regulated by tssM-i3* in X. perforans AL65. We show that TssM-i3* regulates the expression of a suite of genes associated with virulence and metabolism either directly or indirectly by altering the transcription of several regulators. These findings further expand our knowledge on the intricate molecular circuits regulated by T6SS in phytopathogenic bacteria.

Draft Genome Sequences for Five Photorhabdus Bacterial Symbionts of Entomopathogenic Heterorhabditis Nematodes Isolated from India.

Photorhabdus bacteria exhibit contrasting lifestyles; they are virulent insect pathogens but symbionts of the entomopathogenic Heterorhabditis nematodes. Photorhabdus genomes encode several secondary metabolites and insecticidal protein toxins. Here, we present the draft genome sequences for five Photorhabdus strains isolated from Heterorhabditis nematodes collected from various geographical regions of India.