Species-specific function of conserved regulators in orchestrating rice root architecture.

Shoot-borne adventitious/crown roots form a highly derived fibrous root system in grasses. The molecular mechanisms controlling their development remain largely unknown. Here, we provide a genome-wide landscape of transcriptional signatures - tightly regulated auxin response and in-depth spatio-temporal expression patterns of potential epigenetic modifiers - and transcription factors during priming and outgrowth of rice (Oryza sativa) crown root primordia. Functional analyses of rice transcription factors from WUSCHEL-RELATED HOMEOBOX and PLETHORA gene families reveal their non-redundant and species-specific roles in determining the root architecture. WOX10 and PLT1 regulate both shoot-borne crown roots and root-borne lateral roots, but PLT2 specifically controls lateral root development. PLT1 activates local auxin biosynthesis genes to promote crown root development. Interestingly, O. sativa PLT genes rescue lateral root primordia outgrowth defects of Arabidopsis plt mutants, demonstrating their conserved role in root primordia outgrowth irrespective of their developmental origin. Together, our findings unveil a molecular framework of tissue transdifferentiation during root primordia establishment, leading to the culmination of robust fibrous root architecture. This also suggests that conserved factors have evolved their transcription regulation to acquire species-specific function.

Genome-wide discovery of genetic variations between rice cultivars with contrasting drought stress response and their potential functional relevance.

Drought stress is a serious threat to rice productivity. Investigating genetic variations between drought-tolerant (DT) and drought-sensitive (DS) rice cultivars may decipher the candidate genes/regulatory regions involved in drought stress tolerance/response. In this study, whole-genome resequencing data of four DS and five DT rice cultivars were analyzed. We identified a total of approximately 4.8 million single nucleotide polymorphisms (SNPs) and 0.54 million insertions/deletions (InDels). The genetic variations (162,638 SNPs and 17,217 InDels) differentiating DS and DT rice cultivars were found to be unevenly distributed throughout the rice genome; however, they were more frequent near the transcription start and stop sites than in the genic regions. The cis-regulatory motifs representing the binding sites of stress-related transcription factors (MYB, HB, bZIP, ERF, ARR, and AREB) harboring the SNPs/InDels in the promoter regions of a few differentially expressed genes (DEGs) were identified. Importantly, many of these DEGs were located within the drought-associated quantitative trait loci. Overall, this study provides a valuable large-scale genotyping resource and facilitates the discovery of candidate genes associated with drought stress tolerance in rice.

Saccharothrix sp. TD-093 from the Thar Desert, India: Metabolite Fingerprinting of Antimicrobial Compounds and in silico Analysis.

During a screening program for actinomycetes from underexplored and arid Thar Desert (India), TD-093 was isolated. The isolate was characterized based on 16S rDNA sequencing. Aqueous and organic solvent extracts of culture supernatant were investigated for antimicrobial activity. Bioactive fractions, after column chromatography separation, were subjected to GC-MS analysis. Based on 16S rDNA sequence result, isolate TD-093 showed nearest match to Saccharothrix (96%) and is a potential new species. Aqueous and organic solvent extracts showed antimicrobial activity against Staphylococcus epidermidis, Micrococcus luteus, Pseudomonas fluorescens, and Escherichia coli as well as clinical isolates (Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, and Acinetobacter baumannii). GC-MS metabolite fingerprinting resulted in 32 compounds belonging to fatty acid, hydrocarbon, alcohol, aldehyde, amide, ester, ketone, disulfide, and nitrile chemical groups. Combination analyses of the compounds based on retention time, similarity index, mass ion spectra, and retention indices-observed and calculated, showed that many of the compounds could be presumed to be novel. Further, four compounds showed retention indices that have not been documented in databases. In silico analysis (using software Prediction of Activity of Spectra for Substances) of compounds predicted by GC-MS data showed that 21 compounds had potential antibacterial activity.

Integrated transcriptome, proteome and metabolome analyses revealed secondary metabolites and auxiliary carbohydrate metabolism augmenting drought tolerance in rice.

Drought is one of the major consequences of climate change and a serious threat to rice production. Drought stress activates interactions among genes, proteins and metabolites at the molecular level. A comparative multi-omics analysis of drought-tolerant and drought-sensitive rice cultivars can decipher the molecular mechanisms involved in drought tolerance/response. Here, we characterized the global-level transcriptome, proteome, and metabolome profiles, and performed integrated analyses thereof in a drought-sensitive (IR64) and a drought-tolerant (Nagina 22) rice cultivar under control and drought-stress conditions. The transcriptional dynamics and its integration with proteome analysis revealed the role of transporters in regulation of drought stress. The proteome response illustrated the contribution of translational machinery to drought tolerance in N22. The metabolite profiling revealed that aromatic amino acids and soluble sugars contribute majorly to drought tolerance in rice. The integrated transcriptome, proteome and metabolome analysis performed using statistical and knowledge-based methods revealed the preference for auxiliary carbohydrate metabolism through glycolysis and pentose phosphate pathway contributed to drought tolerance in N22. In addition, L-phenylalanine and the genes/proteins responsible for its biosynthesis were also found to contribute to drought tolerance in N22. In conclusion, our study provided mechanistic insights into the drought response/adaptation mechanism and is expected to facilitate engineering of drought tolerance in rice.

Numerical groundwater modelling for studying surface water-groundwater interaction and impact of reduced draft on groundwater resources in central Ganga basin.

Water resources in India's Indo-Gangetic plains are over-exploited and vulnerable to impacts of climate change. The unequal spatial and temporal variation of meteorological, hydrological and hydrogeological parameters has created additional challenges for field engineers and policy planners. The groundwater and surface water are extensively utilized in the middle Gangetic plain for agriculture. The primary purpose of this study is to understand the discharge and recharge processes of groundwater system using trend analysis, and surface water and groundwater interaction using groundwater modelling. A comprehensive hydrological, and hydrogeological data analysis was carried out and a numerical groundwater model was developed for Bhojpur district, Bihar, India covering 2395 km2 geographical area, located in central Ganga basin. The groundwater level data analyses for the year 2018 revealed that depth to water level varies from 3.0 to 9.0 meter below ground level (m bgl) in the study area. The M-K test showed no significant declining trend in the groundwater level in the study area. The groundwater modelling results revealed that groundwater head is higher in the southern part of the district and the groundwater flow direction is from south-west to north-east. The groundwater head fluctuation between the monsoon and the summer seasons was observed to be 2 m, it is also witnessed that groundwater is contributing more to rivers in the monsoon season in comparison with other seasons. Impact of reduction in pumping on groundwater heads was also investigated, considering a 10% reduction in groundwater withdrawal. The results indicated an overall head rise of 2 m in the southern part and 0.2-0.5 m in the middle and northern part of the district.