Bhupendra Chaudhary

Root-specific CKX overexpression enhances root architecture, improves drought resilience, and upregulates stress-responsive gene expression, thereby promoting growth, seed yield, and overall stress tolerance in tobacco under drought stress. Drought stress is a global challenge that reduces crop yields, and is intensified by climate change. Cytokinins (CKs) play a crucial role in plant drought responses which are regulated by enzyme activity and genetic factors. To reveal the physiological effects of cytokinin catabolism on the root architecture under water stress conditions, we perform root-specific ectopic overexpression of the cytokinin-degrading CKX gene using WRKY6 gene promoter in tobacco. The overexpression lines show up to 18% increased plant height, > 30% increase in root length, and over twofold root biomass compared to wild-type (WT) plants. Enhanced root architecture in CKX lines is associated with extent of cytokinin catabolism, which improves nutrient uptake and water absorption, thereby supporting better plant growth. The CKX lines also demonstrate improved drought resilience in both soil- and hydroponic-based systems. Under water stress, the overexpression lines display superior growth, timely flowering, more than a 70% increase in seed formation, and over 27% higher seed germination compared to the WT plants. The CKX lines also maintain better electrolyte balance, higher chlorophyll retention, and increased antioxidant activity. Temporal global gene expression profiling under drought stress in tobacco revealed substantial variations in the number of differentially expressed genes (DEGs), with 6,975 differentially expressed genes after 8 h treatment. Among these DEGs, at least 21 genes were consistently upregulated across all drought stress time points. RT-PCR validation of key drought-responsive genes, viz. NtDREB3, NtP5CS, NtERD, NtLEA5, and NtLTP1 in CKX overexpression lines under water deficit suggest their role in drought adaptation. These findings on the hormonal regulation of root growth could be useful in developing drought-resilient crops.

The overwhelming use of PET plastic in various day-to-day activities led to the voluminous increase in PET waste and growing environmental hazards. A plethora of methods have been used that are associated with secondary pollutants. Therefore, microbial degradation of PET provides a sustainable approach due to its versatile metabolic diversity and capacity. The present work highlights the cutinase enzyme's role in PET degradation. This study focuses on the bacterial cutinases homologs screened from 43 reported phylum of bacteria. The reported bacterial cutinases for plastic degradation have been chosen as reference sequences, and 917 sequences have shown homology across the bacterial phyla. The dienelactone hydrolase (DLH) domain was identified for attaining specificity towards PET binding in 196 of 917 sequences. Various computational tools have been used for the physicochemical characterization of 196 sequences. The analysis revealed that most selected sequences are hydrophilic, extracellular, and thermally stable. Based on this analysis, 17 sequences have been further pursued for three-dimensional structure prediction and validation. The molecular docking studies of 17 selected sequences revealed efficient PET binding with the three sequences derived from the phylum Bacteroidota, the lowest binding energy of -5.9 kcal/mol, Armatimonadota, and Nitrososphaerota with -5.8 kcal/mol. The two enzyme sequences retrieved from the phylum Bacteroidota and Armatimonadota are metagenomically derived. Therefore, the present studies concluded that there is a high probability of finding cutinase homologs in various environmental resources that can be further explored for PET degradation. Graphical abstract

Key message Target mimicry based Gh-miR167 expression diminution illustrated dosage-dependent developmental deformities in floral and boll formation in cotton.

Plant cytokinins (CKs) promote development and physiological processes, drought tolerance, root architecture, and ultimately crop productivity. Biologically active CKs (iP, tZ, and cZ) are precisely maintained in the vegetative and floral tissues through their irreversible degradation by developmentally regulated CK-catabolizing cytokinin oxidase/dehydrogenase (CKX) enzyme. A meta-analysis of CKX proteins was performed through an exhaustive exploration of multiple genome databases of cyanobacteria, bryophyte, monocot and eudicot plants to reveal the intricate evolutionary profiles of CKX enzymes specific to the family Brassicaceae. At least 175 unique paralogous/orthologous CKX sequences were successfully retrieved and phylogenetically clustered into distinct groups. Observations of structural divergences among paralogous sequences compared to their orthologs indicated that the progenitor CKX sequence had been subjected to massive structural modifications, possibly as a result of the evolutionary split between monocots and eudicots. An analysis of dN/dS comparisons of orthologous genes revealed that segmental CKX gene duplications have evolved primarily under purifying selection. Further, 24 CKX genes with conserved signature domain were identified in the amphidiploid Brassica juncea genome (AABB; 2n = 36). Genetic evolution of paralogous and orthologous genes was largely responsible for the expansion of CKX homoeologs in the amphidiploid Brassica genomes. Also, comparative analyses of 1.5 kb-long upstream regulatory regions of BjCKX genes identified various development- and stress-responsive elements. Spatial and temporal expression profiles of CKX genes were primarily attributed to their structural diversity observed in the 5′-regulatory regions along with species evolution. This data suggested that CKX duplicate genes had partitioned their spatial expression (= function) during evolution. These findings illustrated the evolutionary importance of CKX genes during plant development, and also suggested their deployment for future crop improvement programs.